research topics on blockchain technology

Research Topics & Ideas

Blockchain & Cryptocurrency

If you’re just starting out exploring blockchain-related topics for your dissertation, thesis or research project, you’ve come to the right place. In this post, we’ll help kickstart your research by providing a hearty list of research topics and ideas related to blockchain and crypto, including examples from recent studies.

PS – This is just the start…

We know it’s exciting to run through a list of research topics, but please keep in mind that this list is just a starting point . These topic ideas provided here are intentionally broad and generic , so keep in mind that you will need to develop them further. Nevertheless, they should inspire some ideas for your project.

To develop a suitable research topic, you’ll need to identify a clear and convincing research gap , and a viable plan to fill that gap. If this sounds foreign to you, check out our free research topic webinar that explores how to find and refine a high-quality research topic, from scratch. Alternatively, consider our 1-on-1 coaching service .

Blockchain & Crypto-Related Research Topics

• The application of blockchain technology in securing electronic health records.
• Investigating the potential of smart contracts in automating insurance claims.
• The impact of blockchain on the traceability and transparency in supply chain management.
• Developing a blockchain-based voting system for enhancing electoral transparency.
• The role of blockchain in combating counterfeit goods in the luxury goods market.
• Assessing the security implications of quantum computing on cryptocurrency encryption.
• The use of blockchain for royalty distribution in the music industry.
• Investigating the scalability challenges of Ethereum and potential solutions.
• The impact of blockchain technology on cross-border remittances in developing countries.
• Developing a blockchain framework for real-time IoT device management.
• The application of tokenization in real estate asset management.
• Examining regulatory challenges for cryptocurrency exchanges in different jurisdictions.
• The potential of decentralized finance (DeFi) in disrupting traditional banking.
• Investigating the environmental impact of Bitcoin mining and potential sustainable alternatives.
• The role of blockchain in enhancing data security in cloud computing.
• Analysing the impact of Initial Coin Offerings (ICOs) on traditional venture capital funding.
• The use of blockchain for enhancing transparency in charitable organizations.
• Assessing the potential of blockchain in combating online identity theft and fraud.
• Investigating the use of cryptocurrency in illicit trade and its regulatory implications.
• The application of blockchain in automating and securing international trade finance.
• Analysing the efficiency of different consensus algorithms in blockchain networks.
• The potential of blockchain technology in managing intellectual property rights.
• Developing a decentralized platform for peer-to-peer energy trading using blockchain.
• Investigating the security vulnerabilities of various cryptocurrency wallets.
• The role of blockchain in revolutionizing the gaming industry through in-game assets.

Blockchain & Crypto Research Ideas (Continued)

• Assessing the impact of cryptocurrency adoption on monetary policy and banking systems.
• Investigating the integration of blockchain technology in the automotive industry for vehicle history tracking.
• The use of blockchain for secure and transparent public record keeping in government sectors.
• Analysing consumer adoption patterns and trust issues in cryptocurrency transactions.
• The application of blockchain in streamlining and securing online voting systems.
• Developing a blockchain-based platform for academic credential verification.
• Examining the impact of blockchain on enhancing privacy and security in social media platforms.
• The potential of blockchain in transforming the retail industry through supply chain transparency.
• Investigating the feasibility of central bank digital currencies (CBDCs).
• The use of blockchain in creating tamper-proof digital evidence systems for law enforcement.
• Analysing the role of cryptocurrency in financial inclusion in underbanked regions.
• Developing a blockchain solution for secure digital identity management.
• Investigating the use of blockchain in food safety and traceability.
• The potential of blockchain in streamlining and securing e-commerce transactions.
• Assessing the legal and ethical implications of smart contracts.
• The role of blockchain in the future of freelance and gig economy payments.
• Analysing the security and efficiency of cross-chain transactions in blockchain networks.
• The potential of blockchain for digital rights management in the media and entertainment industry.
• Investigating the impact of blockchain technology on the stock market and asset trading.
• Developing a blockchain framework for transparent and efficient public sector audits.
• The use of blockchain in ensuring the authenticity of luxury products.
• Analysing the challenges and opportunities of blockchain implementation in the healthcare sector.
• The potential of blockchain in transforming the logistics and transportation industry.
• Investigating the role of blockchain in mitigating risks in supply chain disruptions.
• The application of blockchain in enhancing transparency and accountability in non-profit organizations.

Recent Blockchain-Related Studies

While the ideas we’ve presented above are a decent starting point for finding a  research topic, they are fairly generic and non-specific. So, it helps to look at actual studies in the blockchain and cryptocurrency space to see how this all comes together in practice.

Below, we’ve included a selection of recent studies to help refine your thinking. These are actual studies,  so they can provide some useful insight as to what a research topic looks like in practice.

• A Novel Optimization for GPU Mining Using Overclocking and Undervolting (Shuaib et al., 2022).
• Systematic Review of Security Vulnerabilities in Ethereum Blockchain Smart Contract (Kushwaha et al., 2022).
• Blockchain for Modern Applications: A Survey (Krichen et al., 2022).
• The Role and Potential of Blockchain Technology in Islamic Finance (Truby et al., 2022).
• Analysis of the Security and Reliability of Cryptocurrency Systems Using Knowledge Discovery and Machine Learning Methods (Shahbazi & Byun, 2022).
• Blockchain technology used in medicine. A brief survey (Virgolici et al., 2022).
• On the Deployment of Blockchain in Edge Computing Wireless Networks (Jaafar et al., 2022).
• The Blockchains Technologies for Cryptocurrencies: A Review (Taha & Alanezi, 2022). Cryptocurrencies Advantages and Disadvantages: A Review (Qaroush et al., 2022).
• Blockchain Implementation in Financial Sector and Cyber Security System (Panduro-Ramirez et al., 2022).
• Secure Blockchain Interworking Using Extended Smart Contract (Fujimoto et al., 2022).
• Cryptocurrency: The Present and the Future Scenario (Kommuru et al., 2022).
• Preparation for Post-Quantum era: a survey about blockchain schemes from a post-quantum perspective (Ciulei et al., 2022).
• Cryptocurrency Blockchain Technology in the Digital Revolution Era (Astuti et al., 2022).
• D-RAM Distribution: A Popular Energy-Saving Memory Mining Blockchain Technology (Jing, 2022).
• A Survey on Blockchain for Bitcoin and Its Future Perspectives (Garg et al., 2022).
• Blockchain Security: A Survey of Techniques and Research Directions (Leng et al., 2022).
• The Importance and Use of Blockchain Technology in International Payment Methods (Erdoğdu & Ünüsan, 2023).
• Some Insights on Open Problems in Blockchains: Explorative Tracks for Tezos (Invited Talk) (Conchon, 2022).

As you can see, these research topics are a lot more focused than the generic topic ideas we presented earlier. So, in order for you to develop a high-quality research topic, you’ll need to get specific and laser-focused on a specific context with specific variables of interest.  In the video below, we explore some other important things you’ll need to consider when crafting your research topic.

Get 1-On-1 Help

If you’re still unsure about how to find a quality research topic, check out our Research Topic Kickstarter service, which is the perfect starting point for developing a unique, well-justified research topic.

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Open Access

Peer-reviewed

Research Article

Where Is Current Research on Blockchain Technology?—A Systematic Review

Affiliation Dept. of Innovation and Software, Lappeenranta University of Technology, Lappeenranta, Finland

Affiliation Dept. of Computer Science & Engineering, Sogang University, Seoul, South Korea

* E-mail: [email protected]

Affiliation Sogang Institute of Advanced Technology, Sogang University, Seoul, South Korea

Affiliation Dept. of Computer Science, Aalto University, Helsinki, Finland

• Jesse Yli-Huumo, 
• Deokyoon Ko, 
• Sujin Choi, 
• Sooyong Park, 
• Kari Smolander

• Published: October 3, 2016
• https://doi.org/10.1371/journal.pone.0163477
• Reader Comments

Blockchain is a decentralized transaction and data management technology developed first for Bitcoin cryptocurrency. The interest in Blockchain technology has been increasing since the idea was coined in 2008. The reason for the interest in Blockchain is its central attributes that provide security, anonymity and data integrity without any third party organization in control of the transactions, and therefore it creates interesting research areas, especially from the perspective of technical challenges and limitations. In this research, we have conducted a systematic mapping study with the goal of collecting all relevant research on Blockchain technology. Our objective is to understand the current research topics, challenges and future directions regarding Blockchain technology from the technical perspective. We have extracted 41 primary papers from scientific databases. The results show that focus in over 80% of the papers is on Bitcoin system and less than 20% deals with other Blockchain applications including e.g. smart contracts and licensing. The majority of research is focusing on revealing and improving limitations of Blockchain from privacy and security perspectives, but many of the proposed solutions lack concrete evaluation on their effectiveness. Many other Blockchain scalability related challenges including throughput and latency have been left unstudied. On the basis of this study, recommendations on future research directions are provided for researchers.

Citation: Yli-Huumo J, Ko D, Choi S, Park S, Smolander K (2016) Where Is Current Research on Blockchain Technology?—A Systematic Review. PLoS ONE 11(10): e0163477. https://doi.org/10.1371/journal.pone.0163477

Editor: Houbing Song, West Virginia University, UNITED STATES

Received: May 10, 2016; Accepted: September 9, 2016; Published: October 3, 2016

Copyright: © 2016 Yli-Huumo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper.

Funding: The author(s) received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Currency transactions between persons or companies are often centralized and controlled by a third party organization. Making a digital payment or currency transfer requires a bank or credit card provider as a middleman to complete the transaction. In addition, a transaction causes a fee from a bank or a credit card company. The same process applies also in several other domains, such as games, music, software etc. The transaction system is typically centralized, and all data and information are controlled and managed by a third party organization, rather than the two principal entities involved in the transaction. Blockchain technology has been developed to solve this issue. The goal of Blockchain technology is to create a decentralized environment where no third party is in control of the transactions and data.

Blockchain is a distributed database solution that maintains a continuously growing list of data records that are confirmed by the nodes participating in it. The data is recorded in a public ledger, including information of every transaction ever completed. Blockchain is a decentralized solution which does not require any third party organization in the middle. The information about every transaction ever completed in Blockchain is shared and available to all nodes. This attribute makes the system more transparent than centralized transactions involving a third party. In addition, the nodes in Blockchain are all anonymous, which makes it more secure for other nodes to confirm the transactions. Bitcoin was the first application that introduced Blockchain technology. Bitcoin created a decentralized environment for cryptocurrency, where the participants can buy and exchange goods with digital money.

However, even though Blockchain seems to be a suitable solution for conducting transactions by using cryptocurrencies, it has still some technical challenges and limitations that need to be studied and addressed. High integrity of transactions and security, as well as privacy of nodes are needed to prevent attacks and attempts to disturb transactions in Blockchain [ 1 ]. In addition, confirming transactions in the Blockchain requires a computational power.

It is important to identify what topics have been already studied and addressed in Blockchain and what are currently the biggest challenges and limitations that need further studies. To address these questions, we decided to use a systematic mapping study process [ 2 ] to identify relevant papers related to Blockchain. In the systematic mapping study, we applied a well-designed research protocol to search for material in scientific databases. The produced map of current research on Blockchain will help other researchers and practitioners in identifying possible research areas and questions for future research.

Although cryptocurrencies are also a business and management topic, we decided to narrow down the research topic to the technical perspective of Blockchain. Our objective was to find and map all papers with technical viewpoints on Blockchain. We were interested in finding Blockchain research topics related to various technical areas, such as security, performance, data integrity, privacy, and scalability.

The rest of the paper is organized as follows. Section 2 introduces the background of Blockchain and Bitcoin. In addition, we present some already identified challenges and technical limitations of Blockchain technology. In Section 3, we describe the applied research methodology and the process of collecting relevant research papers. Section 4 presents the results of the gathered papers and extracted data. Section 5 presents the identified classification schemes. Section 6 discusses the study and answers the research questions. Section 7 concludes the paper.

Blockchain, mostly known as the technology running the Bitcoin cryptocurrency, is a public ledger system maintaining the integrity of transaction data [ 1 ]. Blockchain technology was first used when the Bitcoin cryptocurrency was introduced. To this day, Bitcoin is still the most commonly used application using Blockchain technology [ 3 ]. Bitcoin is a decentralized digital currency payment system that consists of a public transaction ledger called Blockchain [ 4 ]. The essential feature of Bitcoin is the maintainability of the value of the currency without any organization or governmental administration in control. The number of transfers and users in the Bitcoin network is constantly increasing [ 5 ]. In addition, the conversions with traditional currencies, e.g. KRW, EUR and USD, occur constantly in currency exchange markets [ 6 ][ 7 ]. Bitcoin has therefore gained the attention of various communities and is currently the most successful digital currency using Blockchain technology [ 6 ].

Bitcoin uses the public key infrastructure (PKI) mechanism [ 8 ]. In PKI, the user has one pair of public and private keys. The public key is used in the address of the user Bitcoin wallet, and the private key is for the authentication of the user. The transaction of Bitcoin consists of the public key of the sender, multiple public keys of the receiver, and the value transferred. In about ten minutes, the transaction will be written in a block. This new block is then linked to a previously written block. All blocks, including information about every transaction made, are stored in the disk storage of the users, called nodes. All the nodes store information about all recorded transactions of the Bitcoin network and check the correctness of each new transaction made by using previous blocks. The nodes are rewarded by checking the correctness of transactions. This method is called mining, and it is confirmed with Proof-of-Work, which is one of the main concepts of Blockchain technology. When all transactions are successfully confirmed, a consensus exists between all the nodes. The new blocks are linked to previous blocks and all the blocks are aligned in one continuous chain. This chain of blocks is the public ledger technique of Bitcoin, called Blockchain.

Blockchain is the decentralized managing technique of Bitcoin, designed for issuing and transferring money for the users of the Bitcoin currency. This technique can support the public ledger of all Bitcoin transactions that have ever been executed, without any control of a third party organization [ 1 ]. The advantage of Blockchain is that the public ledger cannot be modified or deleted after the data has been approved by all nodes. This is why Blockchain is well-known of its data integrity and security characteristics. Blockchain technology can also be applied to other types of uses. It can for example create an environment for digital contracts and peer-to-peer data sharing in a cloud service [ 1 ]. The strong point of Blockchain technique, data integrity, is the reason why its use extends also to other services and applications.

Blockchain technology has also some technical challenges and limitations that have been identified. Swan [ 1 ] presents seven technical challenges and limitations for the adaptation of Blockchain technology in the future:

• Throughput : The potential throughput of issues in the Bitcoin network is currently maximized to 7tps (transactions per second). Other transaction processing networks are VISA (2,000tps) and Twitter (5,000tps). When the frequency of transactions in Blockchain increases to similar levels, the throughput of the Blockchain network needs to be improved.
• Latency : To create sufficient security for a Bitcoin transaction block, it takes currently roughly 10 minutes to complete one transaction. To achieve efficiency in security, more time has to be spent on a block, because it has to outweigh the cost of double spending attacks. Double-spending is the result of successful spending of money more than once [ 9 ]. Bitcoin protects against double spending by verifying each transaction added to the block chain, to ensure that the inputs for the transaction have not been spent previously [ 9 ]. This makes latency a big issue in Blockchain currently. Making a block and confirming the transaction should happen in seconds, while maintaining security. To complete a transaction e.g. in VISA takes only a few seconds, which is a huge advantage compared to Blockchain.
• Size and bandwidth : At the moment, the size of a Blockchain in the Bitcoin network is over 50,000MB (February 2016). When the throughput increases to the levels of VISA, Blockchain could grow 214PB in each year. The Bitcoin community assumes that the size of one block is 1MB, and a block is created every ten minutes [ 10 ]. Therefore, there is a limitation in the number of transactions that can be handled (on average 500 transaction in one block) [ 11 ]. If the Blockchain needs to control more transactions, the size and bandwidth issues have to be solved.
• Security : The current Blockchain has a possibility of a 51% attack. In a 51% attack a single entity would have full control of the majority of the network’s mining hash-rate and would be able to manipulate Blockchain. To overcome this issue, more research on security is necessary.
• Wasted resources : Mining Bitcoin wastes huge amounts of energy ($15million/day). The waste in Bitcoin is caused by the Proof-of-Work effort. There are some alternatives in industry fields, such as proof-of-stake. With Proof-of-Work, the probability of mining a block depends on the work done by the miner [ 12 ]. However, in Proof-of-Stake, the resource that is compared is the amount of Bitcoin a miner holds [ 12 ]. For example, someone holding 1% of the Bitcoin can mine 1% of the “Proof-of-Stake blocks” [ 12 ]. The issue with wasted resources needs to be solved to have more efficient mining in Blockchain.
• Usability : The Bitcoin API for developing services is difficult to use. There is a need to develop a more developer-friendly API for Blockchain. This could resemble REST APIs.
• Versioning, hard forks, multiple chains : A small chain that consists of a small number of nodes has a higher possibility of a 51% attack. Another issue emerges when chains are split for administrative or versioning purposes.

Overall, Blockchain as a technology has the potential to change the way how transactions are conducted in everyday life. In addition, the applications of Blockchain are not limited to cryptocurrencies, but the technology could be possibly applied in various environments where some forms of transactions are done. The research on the possibilities of Blockchain in applications is certainly an interesting area for future research, but at the moment Blockchain suffers from technical limitations and challenges. Anonymity, data integrity and security attributes set a lot of interesting challenges and questions that need to be solved and assessed with high quality research. Scalability is also an issue that needs to be solved for future needs. Therefore, to identify and understand the current status of research conducted on Blockchain, it is important to gather all relevant research. It is then possible to evaluate what challenges and questions have been tackled and answered, and what are the most problematic issues in Blockchain at the moment.

Research methodology

Systematic mapping study was selected as the research methodology for this study. The goal of a systematic mapping study is to provide an overview of a research area, to establish if research evidence exists, and quantify the amount of evidence [ 2 ]. In this study we follow the systematic mapping process described by Petersen et al. [ 13 ]. We also use guidelines for a systematic literature review described by Kitchenham and Charters [ 2 ] to search for relevant papers. We chose the systematic mapping process as our research methodology because our goal was to explore the existing studies related to Blockchain technology. The results of the mapping study would help us to identify and map research areas related to Blockchain technology and possible research gaps. The process for the systematic mapping study is presented in Fig 1 , and consists of five process steps and outcomes. The Prisma Checklist is provided in S1 Checklist .

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

https://doi.org/10.1371/journal.pone.0163477.g001

Definition of research questions

The first stage of the systematic mapping process is the definition of the research questions. The goal of this study was to provide an overview of the current research on Blockchain technology. Therefore, we defined four research questions:

• RQ1: What research topics have been addressed in current research on Blockchain? The main research question of this mapping study is to understand the current research topics on Blockchain. By collecting all the relevant papers from scientific databases, we would be able to create an overall understanding of Blockchain research and map the current research areas. Mapping the current research done on Blockchain technology will help other researchers and practitioners to gain better understanding on the current research topics, which will help to take the research on Blockchain even further.
• RQ2: What applications have been developed with and for Blockchain technology? Blockchain is mostly known for its relation to Bitcoin cryptocurrency. Bitcoin uses Blockchain technology in currency transactions. However, Bitcoin cryptocurrency is not the only solution that uses Blockchain technology. Therefore, it is important to find the current applications developed by using Blockchain technology. Identifying other applications can help to understand other directions and ways to use Blockchain.
• RQ3: What are the current research gaps in Blockchain research? A systematic mapping of research enables understanding the current research gaps. The identification of research gaps will help other researchers and practitioners to focus their research on areas that require more research. Finding research gaps will help to understand and find unanswered research questions in current Blockchain technology.
• RQ4: What are the future research directions for Blockchain? Understanding the potential future research directions for Blockchain technology is a consequence of RQ1-RQ3. Answering this research question is beneficial when deciding where the research on Blockchain technology should be directed and what issues need to be solved.

Conducting the search

The second stage of a mapping study is to search for all the relevant scientific papers on the research topic. A search protocol defines the methods that will be used to undertake a specific systematic literature search. A pre-defined protocol is needed to reduce the possibility of researcher bias [ 2 ].

We created a search protocol that we used for scientific databases to gather all the papers relevant for our research topic. The terms used in the search string were chosen after pilot searches, where we tested possible keywords. After the pilot search we decided to use only the term Blockchain as the search string, even though Bitcoin could also have been a possible one. However, in the pilot search we used also Bitcoin as a search term, but we identified a huge number of papers that were related to economic topics in cryptocurrencies, rather than technological aspects of Blockchain technology. Therefore, since our goal in this mapping study process was to find and map the papers related to technical aspects of Blockchain technology, we decided to drop the term Bitcoin. We believe that by using only the term Blockchain as the search string, the majority of Bitcoin-related papers with a technical perspective on Blockchain were still included. In addition, it seemed that if a Bitcoin-related paper did not have the term Blockchain anywhere in its meta-data, the paper was related to the economics of a cryptocurrency.

After designing and testing the search protocol, we chose the scientific databases for the searches. We decided to concentrate on peer-reviewed, high quality papers published in conferences, workshops, symposiums, books and journals related to the research topic. We used six scientific databases for paper retrieval. The chosen databases were (1) IEEE Xplore, (2) ACM Digital Library, (3) Springer Link, (4) ScienceDirect, (5) Ebsco, and (6) PLOS One. We decided not to use grey literature e.g. from Google searches, and kept scientific peer review as the criterion.

Screening of relevant papers

Because all papers in the searchers were not necessarily related to the research questions, they needed to be assessed for their actual relevance [ 2 ]. After using the search protocol in the scientific databases, the next stage was the screening of papers. For screening the relevant papers, we used a process inspired by Dybåand Dingsøyr [ 14 ]. At the first screening phase, we screened the papers based on their titles and excluded studies that were not relevant to the research topic. For example, the search protocol returned papers related to Blockchain in other scientific fields, which had different meaning than the Blockchain technology used in computer science. These papers were clearly out of the scope of this mapping study, which was a valid reason to exclude them. However, in some cases it was difficult to determine the relevancy of the paper on the basis of the title of the paper. In these situations, we passed the paper through to the next stage for further reading. In the second phase, the authors read the abstracts of every paper that passed the previous phase. In addition, we used specific inclusion and exclusion criteria to screen each paper. We decided to exclude the following types of papers: (1) papers without full text availability, (2) papers where the main language was not English, (3) papers that had some other meaning than Blockchain used in computer science, (4) papers that were duplicates, and (5) papers that were posters. When a paper passed all the five exclusion criteria, and after reading the abstract it was considered as focusing on Blockchain, we decided to include it in the next screening stage.

Keywording on the basis of the abstract

The next stage in a mapping study process after finding the relevant papers through abstracts is keywording. For this stage, we used the process defined by Petersen et al. [ 13 ] ( Fig 2 ). Keywording was done in two steps. In the first step we read the abstract and identified keywords and concepts that reflected the contribution of the paper [ 13 ]. The second step was to develop a higher level of understanding based on these keywords [ 13 ]. We used the keywords to cluster and form categories for the mapping of the studies. After the categories had been clustered, we read all the selected papers. After the reading we also updated the categories or created new ones, if the paper revealed something new. This resulted in a systematic map of clustered categories formed from all the relevant papers on the research topic.

https://doi.org/10.1371/journal.pone.0163477.g002

Data extraction and mapping process

A data extraction form ( Table 1 ) was designed to collect the information needed to address the research questions of this mapping study [ 2 ]. Data items DI0 to DI6 gathered basic information of the papers. These items included e.g. the title of the paper, the name(s) of the author(s), the country of the author(s), and publication type/place. The rest of the data items (DI7-DI10) were gathered after reading the papers. These data items included e.g. study goals and major findings of each paper. We collected the extracted data items to Excel, which helped us to organize and analyze the data.

https://doi.org/10.1371/journal.pone.0163477.t001

Basic information of the papers

In this section, the search and selection results of the systematic mapping study are presented. Out of the extracted data items ( Table 1 ), this section reports on data items DI0-DI6.

Search and selection results

The search and selection results are presented in Fig 3 . The PRISMA flow diagram is also provided in S1 Diagram . 121 papers were initially retrieved when the designed search protocol was applied to the selected scientific databases. The first inclusion and exclusion round was based on the titles of the retrieved papers. All the paper titles were examined by two authors, which led to the selection of 55 papers. The reason for the high number of excluded papers (66) was that they were not related to the research topic. For example, many excluded papers discussed the business perspective of Bitcoin, and therefore they did not belong to our study. We also retrieved multiple papers related to other scientific areas, such as chemistry and mathematics, where the keyword Blockchain had another meaning than the technology used in computer science.

https://doi.org/10.1371/journal.pone.0163477.g003

After the selection of 55 papers, we removed duplicates and used the next round exclusion and inclusion criteria defined in section 3.3. This round resulted in the selection of 48 papers. After this, three authors read the abstracts of all the selected papers. This did not result in the exclusion of any papers, however. Based on the abstracts, all the selected papers had a topic related to Blockchain with a technical viewpoint.

However, we decided to pass some unclear papers to the next selection round for more in-depth analysis. In the last stage of paper selection, three authors read all the papers. This resulted in the selection of 41 papers, which we included in this study as primary papers. Three papers were dropped due to their focus on the economic perspective of Blockchain and Bitcoin. Additional four papers were excluded for being only reports describing Blockchain and how it works without providing any actual new research findings or evidence. The full list of the selected papers with the extracted data items is presented in S1 Table .

Publication year, source and geographic distribution

Fig 4 shows the publication year distribution of the selected primary papers. Interestingly, all the selected papers were published after the year 2012. This shows that Blockchain as a research area is a very recent and new one. When looking at the publication year distribution more closely, out of all the selected papers, 2 papers (5%) were published in 2013, 16 papers (39%) in 2014 and 23 papers (56%) in 2015. This shows an increasing number of publications each year, which suggests also a growing interest in Blockchain technology. This is not a surprise, because the idea of Blockchain and Bitcoin was first coined only in 2008 [ 4 ].

https://doi.org/10.1371/journal.pone.0163477.g004

Fig 5 shows the source of each selected primary paper. The possible sources for a paper are the academia, industry, or both. Our results showed that 30 papers (73.1%) were published by an academic source and only 3 papers (7.3%) were published by an industry source. In 8 papers (19.5%), the authors were from both academia and industry. It is, however, highly possible that most of the papers published by the industry are not included in scientific databases. Most industry papers can be found as white papers and are not often published in peer-reviewed conferences or journals.

https://doi.org/10.1371/journal.pone.0163477.g005

The geographical distribution of the selected papers is shown in Fig 6 . The largest number of papers (13, 31%) were published by universities or companies in the USA. After this, the two most common publication countries were Germany with 6 papers (14.6%) and Switzerland with 5 papers (12.2%). The rest of the countries had four or less papers published. The geographical distribution of the selected primary papers shows that Blockchain technology has gathered research interest around the world.

https://doi.org/10.1371/journal.pone.0163477.g006

Publication type and channel

Fig 7 shows the publication type of the selected papers. Publication type means the channel where the paper has been published. The publication types included in this mapping study were conference, journal, workshop, symposium, and book chapter. Most of the papers were published in conferences (23) (56%) and workshops (12) (29.2%). The rest of the papers were published in symposiums (4) (9.7%), as a book chapter (1) (2.4%), or in a journal (1) (2.4%). In addition, Table 2 shows the publication channel of each selected paper. Most papers were published in conferences and workshops in the International Conference on Financial Cryptography and Data Security (FC) (13) (31.7%). 3 or less of the selected papers had used other publication channels.

https://doi.org/10.1371/journal.pone.0163477.g007

https://doi.org/10.1371/journal.pone.0163477.t002

Classification of the relevant papers

In this section, the classification of the selected primary papers is presented, including extracted data items DI7-DI10 ( Table 1 ). After reading all the selected papers and creating classifications based on the findings, we identified that a majority of the papers were related to the technical challenges and limitations presented by Swan [ 1 ]. Therefore, we decided to use these challenges and limitations for the classification to map the existing research on Blockchain. The challenges and limitations presented by Swan are throughput, latency, size and bandwidth, security, wasted resources, usability, versioning, hard forks, and multiple chains. In addition, we identified a new classification type, privacy. Privacy in an essential attribute in the Blockchain environment, because of its anonymity characteristic. In addition, we also used the class others to map papers that were not related to any of the classes mentioned above.

We also identified that there were three different paper types for each class, Blockchain report, Blockchain improvement and Blockchain application. A Blockchain report includes papers that report previously identified solutions and ideas in Blockchain and Bitcoin. A Blockchain improvement includes papers that suggest new solutions and improvements to the current Blockchain or Bitcoin technology. A Blockchain application includes papers that present an application based on Blockchain technology. The final map of this study is presented in Fig 8 .

https://doi.org/10.1371/journal.pone.0163477.g008

We also decided to examine the papers based on their relation to Bitcoin ( Fig 9 ), because it is considered so far the most important and commonly used solution based on Blockchain technology. As expected, a great number of papers were related to Bitcoin, rather than other applications. In 33 (80.5%) of the selected papers, the research was conducted in the Bitcoin environment. We found only 8 papers (19.5%) that did focus on Bitcoin, but on other applications using Blockchain technology.

https://doi.org/10.1371/journal.pone.0163477.g009

We also made a comparison between the paper type (Blockchain report, Blockchain improvement, and Blockchain application) and the publication year. The comparison is shown in Fig 10 . The figure shows an increasing number of papers in both report and application categories over the three years. Improvement papers had a significant increase in 2014, but a decrease in 2015.

https://doi.org/10.1371/journal.pone.0163477.g010

Security was the one of the major research topics in the selected primary papers. 14 out of the 41 papers (34%) were related to challenges and limitations in Blockchain and Bitcoin security. We identified various topics in security, including trends and impacts of security incidents, 51% attack, data malleability problems, and authentication and cryptography issues.

Trends and impacts of security incidents : With the increasing use of Bitcoin as a way to conduct payments and transfers, security incidents and their impact on the economic losses of Bitcoin users have increased. Some of the identified papers presented security incidents that had occurred in the Bitcoin network, such as economic losses by several Bitcoin scams and distributed denial-of-service (DDoS) attacks on exchanges and mining pools. Vasek et al. [ 33 ] investigated four types of Bitcoin scams (Ponzi scams, mining scams, scam wallet and fraudulent exchanges) by tracking online forums and voluntary vigilantes. The authors noted that $11 million had been contributed to scams by 13000 victims in Bitcoin from September 2013 to September 2014. Lim et al. [ 48 ] analyzed the trend of security breaches in Bitcoin and their countermeasures. According to the authors, all possible types of security breaches had occurred, including DDoS attacks, private account hacking using Trojan horses, or viruses from ads. The authors introduce some security countermeasures for individual users and safe Bitcoin transactions (e.g. a hardware wallet and a hardware authentication device). Vasek et al. [ 27 ] present evidence on DDoS attacks in the Bitcoin network using DDoS-related posts in the popular Bitcointalk.org forum. The authors figured out that the most targeted service category was the use of anti-DDoS protection, influencing factors such as the mining pool size. The major findings of the study were that the most often targeted service was currency exchange (41%), followed by mining pools (38%). According to the paper, 54% of the services that had experienced DDoS attacks had anti-DDoS protection, although it was not certain whether they had the protection on at the time of attack. In addition, of the services that had not yet experienced a DDoS attack, only 15% had anti-DDoS protection. The paper concludes that over 60% of large mining pools have suffered DDoS attacks, compared to 17% of small pools.

51% Attack : The Blockchain mechanism is designed with the assumption that honest nodes control the network [ 4 ]. If attacker nodes collectively control more computational power than the good ones, the network is vulnerable to the so called 51% Attack. Beikverdi et al. [ 20 ] argue that although the Bitcoin itself is designed as a fully decentralized network, market-based centralization of mining power by a few large mining pools increase the risk of a 51% Attack. Their study shows that the centralization factor of Bitcoin has been continuously increasing from 2011 (0.26) to 2014 (0.33). In this context, 0 means purely decentralized and 1 means fully centralized. Moreover, there are studies claiming that the 1/2 assumption of computational power is not enough for security. Garay et al. [ 39 ] propose applications built on the core of the Bitcoin protocol focusing on the Byzantine agreement (BA), which is the fundamental scientific problem for decentralized transaction agreement in the Bitcoin network. The suggested application presents a simple BA protocol with the assumption that the adversary’s hashing power is bounded by 1/3. Eyal and Sier [ 30 ] introduce a Selfish Mine attack where colluding miners obtain a revenue larger than a fair share by keeping their discovered blocks private. The authors propose a protocol modification which commands less than 1/4 of the total computation power.

The more recent Blockchain-based systems, such as Ethereum, allow users to specify scripts in transactions and contracts to support applications beyond simple cash transactions. In this case, the required computational resources for verification could be larger, depending on the user-specified script size. Luu et al. [ 46 ] present a security attack called the verifier’s dilemma, which drives rational miners to skip verification where the verifying transactions require significant computational resources in Bitcoin and especially in Ethereum. The authors formalize a consensus model to give incentives to miners by limiting the amount of work required to verify a block.

Armknecht et al.[ 42 ] explain how to support security and privacy in the Ripple system, which is one of the consensus-based distributed payment protocols. The paper discusses the basic difference between the protocol of Ripple and Bitcoin-focused Blockchain fork. A fork can occur if two conflicting ledgers get a clear majority of votes, and could lead to double spending attacks. According to Decker and Wattenhofer [ 52 ], the propagation delay in the Bitcoin network is the primary cause for Blockchain forks and inconsistencies among replicas, which was done by analyzing Blockchain synchronization mechanism.

Data malleability problems : Data integrity is an essential issue in the Blockchain environment. It is necessary that when data gets sent and verified, it has not been altered or tampered with. We found two studies related to data integrity that studied malleability attacks in Blockchain. Malleability describes the fact that the signatures that prove the ownership of Bitcoin being transferred in a transaction do not provide any integrity guarantee for the signatures themselves [ 36 ]. Therefore, in a malleability attack an attacker intercepts, modifies, and rebroadcasts a transaction, causing the transaction issuer to believe that the original transaction was not confirmed [ 36 ].

Decker & Wattenhoffer [ 36 ] studied transaction malleability in Bitcoin environment and used a real-life case as an example. According to the paper, the transaction malleability problem is real and should be considered when implementing Bitcoin clients. Andrychowicz et al. [ 31 ] made a similar study by conducting practical experiments which presented a high possibility of a malleability attack and its impact. In their study, the malleability attack caused incorrect balance computing, application crashes, and a deadlock which stopped new transactions in several well-known Bitcoin wallets. The paper suggests a deposit protocol with a timed commitment scheme to enable a malleability-resilient refund transaction as a solution to the malleability problem.

Authentication and cryptography issues : In Bitcoin, the private key is the major authentication element. Authentication in cryptocurrency controls self-certification. There have been some incidents with authentication. For example, there is the well-known case in Mt.Gox, where a Bitcoin wallet company was attacked. In the attack, Mt.Goxs storage that included private keys of their customer was stolen. This incident has motivated some studies in strengthening authentication in Bitcoin. In addition to the Mt.Gox case, Bos et al. [ 26 ] state that the use of elliptic curve cryptography (ECC), which is used to derive Bitcoin addresses to users, is insufficient and does not have the required randomness.

We identified a number of papers that had the goal to address the issues in the Bitcoin authentication process. Bamert et al. [ 18 ] suggest a Bitcoin hardware token, the BlueWallet. The device communicates by using Bluetooth Low Energy, and is able to secure and sign Bitcoin transactions. Ateniese et al. [ 19 ] propose a certification system for Bitcoin that offers an opt-in guarantee to send and receive Bitcoins only to/ from certified users, and control of the creation of Bitcoins addresses by trusted authorities. According to the paper, this approach improves the trustworthiness of real-world entities into the system, which mitigates the existing reservations to the adoption of Bitcoin as a legitimate currency. Mann et al. [ 17 ] suggest two-factor authentication for a Bitcoin wallet. The authors used a smart phone as the second authentication factor. The solution can be used with hardware already available to most users, and the user experience/interface has similarities to the existing online banking authentication methods.

Wasted resources

The energy efficiency problem is not handled in the computer engineering field at the moment. However, in special domains like mobile cloud computing, it might be one of the major issues in the future [ 55 ]. Mining Bitcoins requires a high amount of energy to compute and verify transactions securely and with trustworthiness [ 1 ]. However, for the efficiency of mining and Proof-of-Work, it is important to decrease the amount of wasted resources.

We identified some papers related to the wasted resource problems in Bitcoin. Wang and Liu [ 21 ] present the evolution of Bitcoin miners in terms of volume of solo and pool miners and their productivity. In the early stages, the computation power was evenly distributed among the solo miners. As the Bitcoin network evolved, the computation power of some pool miners increased. The study notes that all miners play a zero-sum-computation race game: each miner increases their computation power, and then the total computation power in the network increases; consequently the system increases the difficulty value to maintain a steady Bitcoin creation speed, which in turn reduces the Bitcoin mining rate of individual miners [ 21 ].

We also identified some papers that proposed solutions for the wasted resources problem in Blockchain and Bitcoin. Wang and Liu [ 21 ] suggest an economic model for getting high economic returns in consideration of the use of mining hardware with high computation-over-power efficiency and electricity price. Paul et al. [ 16 ] have calculated and show how a new scheme can lead to an energy-efficient Bitcoin. The authors modified the present block header by introducing some extra bytes to utilize the timestamp more effectively. The suggested scheme uses less computing power, and thus the mining is more environment-friendly. Anish [ 15 ] proposes methods of achieving contextually higher speeds of Bitcoin mining, involving simultaneous usage of CPUs and GPUs in individual machines in mining pools. The results presented in the paper show how standard hardware miners in large mining pools could quite significantly add to the overall hash rate. Barkatullah et al. [ 54 ] describe the architecture and implementation details of a CoinTerras first-generation Bitcoin mining processor, Goldstrike 1, and how this processor was used to design a Bitcoin mining machine called Terraminer IV, especially about how high power density issues were solved and energy efficiency increased.

The original definition of the challenges and limitations in the usability of Blockchain by Swan [ 1 ] describes Bitcoin API as hard and difficult to use. This definition can be viewed mainly from the developer’s perspective, where Bitcoin API is hard to implement and use in and with other services and applications. We did not find any papers related to the usability issue from the software developer’s perspective. However, we found several papers that considered the usability of Bitcoin from the cryptocurrency user’s perspective. Therefore, we decided to expand the original definition of Blockchain usability to take usability into account also from the point of view of the cryptocurrency user.

An important factor in Blockchain usability from the user’s perspective is the ability to analyze Blockchain. In Blockchain, new blocks are created constantly and confirmed by miners, which creates an interesting environment of transaction flows. It is therefore essential to have supporting tools to help users analyze the whole Blockchain network to improve the usability. We found applications that had been developed for this purpose. BitConeView [ 51 ] is a system for the visual analysis of Bitcoin flows in Blockchain. BitIodine [ 23 ] parses Blockchain, clusters addresses that are likely to belong to the same user or group of users, classifies such users and labels them, and finally visualizes the complex information extracted from the Bitcoin network. Both these systems were tested successfully with experiments and cases, and showed effectiveness in analyzing and detecting patterns in the Bitcoin network. These systems can help also in improving security and privacy -related issues.

Bankruptcy and the closure of Bitcoin exchanges can cause economical damage to the customers [ 38 ]. Decker et al. [ 38 ] propose an audit software to improve usability in Bitcoin exchanges. The goal of the software is to prove the exchange participants’ solvency without publishing important information. In addition, Vandervort [ 25 ] discusses the link between a buyer and a seller with a layer of limited anonymity, thus preventing buyers from finding or validating information in Bitcoin. The paper presents three different models by which a reputation/rating system could be implemented in conjunction with Bitcoin transactions, and considers the pros and cons of each. Improving these aspects of exchanges done in the Bitcoin network can improve the usability by providing additional information for the users making the transactions.

Throughput, latency, size and bandwidth, and versioning, hard forks, multiple chains

Interestingly, we did not identify any papers that were related to other technical challenges and limitations, such as throughput, latency, size and bandwidth, versioning, hard forks, and multiple chains.

In a Blockchain network, a distributed consensus network without a trusted party, all the transactions are transparent and announced to the public. Therefore, privacy in Blockchain is maintained by breaking the flow of information. The public can see all transactions, but without information linking the transaction to identities [ 4 ]. For this security model, 10 studies out of 41 (24%) proposed privacy issues and countermeasures to increase anonymity in Blockchain.

Meiklejohn and Orlandi [ 32 ] present a definitional framework of anonymity focusing on the ownership of the coin. There are also studies that show experimental evidence on the lack of anonymity in the Bitcoin network. Koshy et al. [ 35 ] analyzed a traffic pattern in Bitcoin and conclude that some subset of Bitcoin addresses can be mapped to an IP address simply by observing the transaction relay traffic. Feld et al. [ 53 ] introduce a framework to traverse the Bitcoin network and generate statistics based on that. By using the tool, the authors figured out that an average peer-list contains addresses that mostly reside in the own autonomous systems of the peers. Taking this information into account, the authors claim that transaction linking could be possible.

Similar to our mapping study, Herrera-Joancomartí [ 6 ] provide an exhaustive review of papers on Bitcoin anonymity research. according to the author, very few papers have been published regarding the traffic of Bitcoin that may reveal private information. In order to solve the anonymity reduction, a mix of services has been proposed in some papers. A number of studies have applied a transaction mixing technique to increase privacy. A mixing transaction allows the users to move Bitcoins from one user address to another without a clear trace linking between the addresses. Such transactions can act as a primitive to help improve anonymity when transaction linking becomes more challenging.

Valenta and Rowan [ 24 ] have modified the Mixcoin protocol to prevent the mix from learning the input/output address mappings of participating users. The authors propose a system, Blindcoin, which modifies the Mixcoin mixing protocol by using blind signatures and a public append-only log. The log makes it possible for a third party to verify the validity of accusations when blind signatures are used. Ziegeldorf et al. [ 47 ] present CoinParty, a decentralized mixing service for Bitcoin based on a combination of decryption mix-nets with threshold signatures. According to the authors, CoinParty is secure against malicious adversaries, and the evaluation of their prototype shows that it scales easily to a great number of participants in real-world network settings. Ruffing et al. [ 37 ] propose CoinShuffle, a completely decentralized Bitcoin mixing protocol that allows the users to utilize Bitcoin in a truly anonymous manner. It does not require any (trusted, accountable or untrusted) third party and it is compatible with the current Bitcoin system. CoinShuffle introduces only a small communication overhead for its users, while avoiding additional anonymization fees and minimizing the computation and communication overhead for the rest of the Bitcoin system. Androulaki et al. [ 41 ] propose a solution, an extension of ZeroCoin (EZC), to hide transaction value and address balances in Bitcoin for increased privacy. ZeroCoin acts as a temporary currency to impede the traceability of coins, but it does not hide the number of transactions and balances of Bitcoin addresses. The proposed improvements include mixing Bitcoins from various sources before sending them to a destination and enabling payments in the form of EZC without the need to transform them back to Bitcoin. For the effectiveness of mixing techniques in improving anonymity, Möser et al. [ 49 ] present analysis results on some available Bitcoin mixing services. The test results showed that linking the input and output transactions was possible in 1 out of 3 tested services. Other than mixing techniques, Saxena et al. [ 28 ] suggest use of composite signatures to prevent linking between sending and receiving addresses.

Smart contracts, new cryptocurrencies, botnet, broadcast protocol, trustworthiness

We also identified other classifications that were not included in the seven technical challenges and limitations defined by Swan [ 1 ]. Three of the papers were related to the use of Smart contracts in the Blockchain environment. A smart contract is a solution that utilizes Blockchain technology to create contracts between two or more participants. Similarly to the use of Bitcoin Blockchain, smart contracts are done in a decentralized environment, where contract terms are executed by the Blockchain systemwhen the terms are fulfilled. Bigi et al. [ 45 ] introduce a decentralized smart contract protocol inspired by BITHALO and validated the feasibility of the protocol based on the protocols of Bitcoin. The approach is a combination of the game theory and formal models. The authors argue that a decentralized smart contract system can be a promising approach and worthy of being studied and developed further. Wan et al. [ 43 ] propose an electronic signing protocol between two parties using the Bitcoin network as a way of providing a time-stamping service. In addition, smart contracts can be possibly used in various environments and industries for different purposes. For example, Kishigami et al. [ 50 ] provide a Blockchain-based digital content distribution system and show a prototype of the concept. The idea was presented to one hundred people including creators, content owners and digital content stake holders. The feedback showed that the most impressive point was the decentralized mechanism for Digital Right Management. However, the proposed system has no incentive mechanism for mining calculation, which can make it a challenge to adopt at the moment.

Even though Bitcoin is the most famous and commonly used cryptocurrency adopting Blockchain technology, there has also been research on developing other cryptocurrencies. Zhang and Wen [ 22 ] have designed a new generation cryptocoin called IoTcoin, based on the protocol of Bitcoin and Blockchain. In IoT-coin, people can use keys and scripts which are obtained in them to exchange paid sensor data or smart property. IoTcoins can be used to present the ownership of many IoT commodities, such as smart property, paid data and digital controlled energy. Another cryptocurrency has been proposed by Vandervort et al. [ 29 ] as a model of a community cryptocurrency with a community fund feature.

We also found three papers that used Blockchain for Botnet networks, a P2P broadcast protocol, and a trustworthiness improvement. Ali et al. [ 34 ] ppresent Zombiecoin, which runs in Bitcoin networks and offers a Botnet C&C (command-and-control) mechanism. Botnet networks include a number of computers communicating in an effort to compute representative tasks. However, the weak point for botnet is the C&C infrastructure. The Bitcoin transaction can be used as a communication vehicle. Andrychowicz and Dziembowsk [ 40 ] ppresent a formal model for peer-to-peer communication and a Proof-of-Work concept used in Bitcoin, and based on the model, propose a broadcast protocol which is more secure against an adversary with arbitrary computational power. Wilson and Ateniese [ 44 ] have adopted the Bitcoin technology to enhance the Pretty Good Privacy (PGP) mechanism. In this mechanism, a Bitcoin address, Bitcoin identity verification transactions, and a Blockchain key server are used to improve the user’s trustworthiness.

Summary of the identified challenges/limitations and suggested solutions in Blockchain

In Fig 11 we summarize the identified challenges and suggested solutions in Blockchain and Bitcoin.

https://doi.org/10.1371/journal.pone.0163477.g011

In this chapter we discuss the results and answer the four main research questions. In addition, at the end of this chapter, we discuss the limitations and validity of the study.

RQ1: What research topics have been addressed in current research on Blockchain?

The results of this mapping study showed that a majority of the current research on Blockchain is focused on finding and identifying improvements to the current challenges and limitations in Blockchain [ 1 ]. A large portion of the research concentrates on security and privacy issues in Blockchain.

The security vulnerability of the Blockchain network and the growing interest in Bitcoin have increased the economic losses of both miners and end users. The identified vulnerabilities include computation power -based attacks, such as the 51% attack, selfish mine attack, transaction data malleability problems, and deanonymization by transaction linking. Although several solutions to address these issues have been presented, many of them are just brief idea suggestions, lacking concrete evaluation of their effectiveness.

The research on other topics in challenges and limitations described by Swan [ 1 ], such as wasted resources and usability, was rather limited. We found some research done on computational power and wasted resources in Bitcoin mining, and improvements on the usability of Bitcoin. However, the number of papers was considerably small compared to those on security and privacy issues. Computational power is one of the key attributes in Blockchain, and it requires attention in the research. When Blockchain grows more complex, it also requires more computational power to confirm more blocks. The Proof-of-Work concept is a rather new idea, which is the reason why it has to be studied more, to make sure that it can work in large-scale Blockchain environments.

Interestingly, we did not find many studies on challenges and limitations in latency, size and bandwidth, throughput, versioning, hard forks, and multiple chains. It is surprising that the attention paid to and research done on other challenges and limitations than security and privacy was rather low. We assumed that especially topics like latency, size and bandwidth, and wasted resources would have received more attention in the overall research map. When the size of Blockchain increases, it has a direct impact on all these challenges and limitations in scalability. It is possible that these issues have not been studied a lot because the Blockchain concept is still rather new.

In addition to the identified research topics, the findings in this mapping study showed that a majority of research was conducted in the Bitcoin environment. This was also the original assumption of the authors, considering that Bitcoin is currently the most commonly used and important technology using Blockchain, with the largest user base. However, we were quite surprised that the number of other solutions than Bitco using Blockchain was so low. The results showed that the research outside the Bitcoin environment was mostly focused on smart contracts and other cryptocurrencies, but the research on Bitcoin and its security issues formed the majority.

RQ2: What applications have been developed with and/to Blockchain technology?

We originally defined a Blockchain application as a solution that has been developed with Blockchain technology. By this definition, we identified some prototype applications developed and suggested for using Blockchain in other environments, such as IoT, smart contracts, smart property, digital content distribution, Botnet, and P2P broadcast protocols. This shows that Blockchain technology is not limited to applications in cryptocurrencies. Instead, the idea of a public ledger and a decentralized environment can be applied to various other applications in different industries, which makes the whole Blockchain research more interesting.

However, we also found a set of different applications developed for the Bitcoin environment, rather than using Blockchain technology in some other environment. Some of the applications were developed for Bitcoin analysis. Applications like BitConeView [ 51 ] and BitIodine [ 23 ] help users to analyze the Bitcoin network and study how Bitcoin transactions are completed, with a visual presentation. These types of applications can help to understand the essence of Blockchain, and how a decentralized transaction environment actually works. Analysis applications can also help to identify frauds and possible security issues by following the flows of transactions.

Another major direction for applications is security. We found applications where the focus was on Bitcoin mixers. Bitcoin mixing applications, such as CoinParty [ 47 ] and CoinShuffle [ 37 ] can help the Bitcoin network to become more secure, by adding an extra layer of privacy for the users. These types of applications and solutions will likely increase in the future, considering that security and privacy are the main attributes in a decentralized transaction environment.

RQ3: What are the current research gaps in Blockchain research?

We were able to identify a few major research gaps. The first gap is that the research on topics such as latency, throughput, size and bandwidth, versioning, hard forks, and multiple forks does not exist in the current literature. This is a major research gap, which requires more research in the future. These topics are not possibly the most interesting topics for researchers at the moment, because the sizes of the current Blockchain applications are relatively small. Bitcoin is currently the largest solution with Blockchain. The number of transactions in Bitcoin is considerably smaller than e.g. in VISA. However, in the future, if Blockchain solutions are used by tens of millions of people and the number of transactions is multiplied drastically, more research on e.g. latency, size and bandwidth, and wasted resources needs to be conducted to ensure scalability.

The second research gap is the lack of research on usability. We identified only papers that discussed usability from the user perspective, not from the developer perspective, as suggested by Swan [ 1 ]. For instance, the difficulty of using Bitcoin API has not been tackled yet. This needs to be studied and improved in the future. This could spark more applications and solutions to the Bitcoin environment.

The third research gap is that the majority of current research is conducted in the Bitcoin environment, rather than in other Blockchain environments. Research on e.g. smart contracts needs to be carried out to increase knowledge outside cryptocurrencies. Even though Blockchain was first introduced in the cryptocurrency environment, the same idea can be used in various other environments. Therefore, it is necessary to conduct research on the possibilities of using Blockchain in other environments, because it can reveal and produce better models and possibilities for doing transactions in different industries.

The fourth research gap can be found in the low number of high quality publications in journal level publication channels. Currently most of the research is published in conferences, symposiums and workshops. There is a need for high quality journals where the focus is on Blockchain.

RQ4: What are the future research directions for Blockchain?

The future research directions for Blockchain are not clear, and it is interesting to see where it is heading. On the other hand, Bitcoin has received a lot of attention as a cryptocurrency, and more people are trading and buying Bitcoins every day. Therefore, it is highly possible that Bitcoin is important as one of the future research topics, and it will attract industry and academia to conduct more research from both business and technical perspectives.

Bitcoin is only one solution using Blockchain technology. There are also a lot of other cryptocurrencies at the moment, competing with Bitcoin to be the world’s primary cryptocurrency. We believe that future research will also include research conducted on other cryptocurrencies. However, at the moment it seems that Bitcoin has by far the largest market share, and it will be a challenge for other cryptocurrencies to compete with it.

However, we believe that future research will not only focus on Bitcoin and other cryptocurrencies, but on other possible applications using Blockchain as a solution. We already found some papers that studied the possibility of using smart contracts, licensing, IoT, and smart properties in the Blockchain environment. We believe that this type of research will have a lot of impact in the future, and can possibly be even more interesting than cryptocurrencies. To use a decentralized environment in e.g. sharing a virtual property could be a solution that revolutionizes the way companies can sell their products. Taking this in consideration, we strongly believe that when Blockchain technology gets adopted more by both industry and academia, it will generate a significant amount of new research.

When more Blockchain solutions are taken in use with larger numbers of users, it will also have an impact on the research done on technical limitations and challenges. In the future, increased sizes and user bases in various Blockchains will trigger the need to conduct more research on the challenges and limitations in topics related to scalability. In addition, the security and privacy of Blockchain will be always a topic for research, when new ways are invented to disturb and attack Blockchain. Although Blockchain is a rather new technology, there already exist profound studies in each problem domain including security and distributed system literature (for example, multi-level authentication technique [ 56 ], energy-efficient resource management for distributed systems [ 55 , 57 ], and etc.). A closer look and adoption of proven solutions would accelerate overcoming current challenges and limitations of Blockchain technology.

Limitations of the systematic mapping study

The principal limitations of a systematic mapping study are related to publication bias, selection bias, inaccuracy in data extraction, and misclassification [ 58 ].

Publication bias refers to the problem that positive results are more likely to be published than negative ones, since negative results take longer to be published or are cited in other publications to a lesser extent [ 2 ][ 58 ]. To address this issue, we used several well-known scientific databases in the search protocol to find as many papers as possible. This increased the number of papers we were able to find for this mapping study, which to some extent also increased the possibility to find papers with negative results. However, considering that Blockchain technology is rather a new topic in computer science industry and academia, it is possible that research has been conducted in the industry and published as white papers or internally within companies. Therefore, all research conducted on the technical aspects on Blockchain might not be included in this mapping study. However, by using only scientific databases as a source for finding relevant research, we were able to collect papers that were probably of a higher quality.

Selection bias refers to the distortion of statistical analysis owing to the criteria used to select the publications [ 58 ]. We addressed this issue by designing our search protocol carefully. We also conducted a pilot search with different keywords, to ensure that we included as many papers as possible in this mapping study. We defined rigorous inclusion and exclusion criteria, to ensure that all the selected papers were part of our research topic, and answered the research questions. However, there is one major limitation that needs to be addressed. Our search protocol included only the term Blockchain. There is a possibility that not all the research related to Blockchain was found due to our search protocol for paper retrieval. Much of the research related to Blockchain concerns economic, legal, or regulation aspects of Bitcoin and its possibilities as a cryptocurrency. Our goal was to study the technical aspects of Blockchain, rather than trying to understand how Bitcoin as a cryptocurrency can work in the real-world environment. Based on our pilot search, we believe that we were able to retrieve a majority of the relevant papers by using only Blockchain as the search term.

Inaccuracy in data extraction and misclassification refer to the possibility that information is extracted differently by different reviewers [ 58 ]. We addressed this issue by using three authors in the paper retrieval process. All three authors went through the abstracts of the selected papers, and gave their opinion on including or excluding the paper. In a situation where the opinions did not match, we had a discussion to address whether that specific paper should be included or excluded. In addition, the classifications of the papers were done in several face-to-face meetings, where the three authors discussed and created classifications and mappings to all the 41 selected primary papers.

Blockchain technology runs the Bitcoin cryptocurrency. It is a decentralized environment for transactions, where all the transactions are recorded to a public ledger, visible to everyone. The goal of Blockchain is to provide anonymity, security, privacy, and transparency to all its users. However, these attributes set up a lot of technical challenges and limitations that need to be addressed.

To understand where the current research on Blockchain technology positions itself, we decided to map all relevant research by using the systematic mapping study process [ 2 ]. The goal of this systematic mapping study was to examine the current status and research topics of Blockchain technology. We excluded the economic, law, business, and regulation perspectives, and included only the technical perspective. We extracted and analyzed 41 primary papers from scientific databases. We provide recommendations on future research directions of Blockchain technology based on the current research status as following:

• Continue to identify more issues and propose solutions to overcome challenges and limitations of Blockchain technology. The interest on Blockchain technology has been drastically increased since 2013. The cumulative number of papers is increased from 2 in 2013 to 41 in 2015. Majority of the studies has been focused on addressing the challenges and limitations, but there still exist many issues without proper solutions.
• Conduct more studies on scalability issues of Blockchain. Most of the current research on the Blockchain technology is focused on security and privacy issues. To be ready for pervasive use of Blockchain technology, scalability issues such as performance and latency have to be addressed.
• Develop more Blockchain based applications beyond Bitcoin and other cryptocurrency systems. The current research is focused on Bitcoin system. However, the research also shows that Blockchain technology is applicable for other solutions such as smart contracts, property licensing, voting etc.
• Evaluate the effectiveness of the proposed solutions with an objective evaluation criteria. Although several solutions to challenges and limitations have been presented, many of them are just brief idea suggestions and lack concrete evaluation on their effectiveness.

Supporting Information

S1 table. the full list of selected primary papers..

https://doi.org/10.1371/journal.pone.0163477.s001

S1 Checklist. PRISMA Checklist.

https://doi.org/10.1371/journal.pone.0163477.s002

S1 Diagram. PRISMA Flow diagram.

https://doi.org/10.1371/journal.pone.0163477.s003

Author Contributions

• Conceptualization: JY DK SC SP KS.
• Data curation: JY DK SC.
• Formal analysis: JY DK SC.
• Investigation: JY DK SC.
• Methodology: JY DK SC.
• Project administration: SC.
• Resources: SP KS.
• Supervision: SP KS.
• Visualization: JY.
• Writing – original draft: JY DK.
• Writing – review & editing: JY DK SC.
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A Systematic Overview of Blockchain Research

Blockchain has been receiving growing attention from both academia and practices. This paper aims to investigate the research status of blockchain-related studies and to analyze the development and evolution of this latest hot area via bibliometric analysis. We selected and explored 2451 papers published between 2013 and 2019 from the Web of Science Core Collection database. The analysis considers different dimensions, including annual publications and citation trends, author distribution, popular research themes, collaboration of countries (regions) and institutions, top papers, major publication journals (conferences), supportive funding agencies, and emerging research trends. The results show that the number of blockchain literature is still increasing, and the research priorities in blockchain-related research shift during the observation period from bitcoin, cryptocurrency, blockchain, smart contract, internet of thing, to the distributed ledger, and challenge and the inefficiency of blockchain. The findings of this research deliver a holistic picture of blockchain research, which illuminates the future direction of research, and provides implications for both academic research and enterprise practice.

1 Introduction

With the era of bitcoin, digital cash denoted as BTC makes it possible to store and transmit value through the bitcoin network [ 1 ] . And therewith, blockchain, the technology underlying bitcoin, which adopts a peer-to-peer network to authenticate transactions, has been gaining growing attention from practices, especially Libra, a global currency and financial infrastructure launched by Facebook, and digital currency electronic payment. Currently, blockchain is also an increasingly important topic in the academic field. Blockchain research has considerably progressed, attracting attention from researchers, practitioners, and policy-makers [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ] .

Considering the huge potential benefits that blockchain would bring in various aspects of industries, for instance, finance and economy [ 10 , 11 , 12 ] , internet of things [ 13 , 14 , 15 ] , energy [ 16 , 17 ] , supply chain [ 18 , 19 ] , and other areas. It is often compared with the Internet and is even referred to as a new form of the Internet. As a result, the number of publications in the blockchain is growing rapidly. According to an initial search on the Web of Science Core Collection, over 2000 scientific papers published are related to blockchain.

Under the circumstances where the number of research publications in the blockchain is quickly increasing, although studies have tried to provide some insights into the blockchain research via literature reviews [ 20 , 21 , 22 , 23 , 24 ] . Comprehensive scientometric analysis of academic articles published in influential journals are beneficial to the further development of blockchain research. This research conducts a bibliometric visualization review and attempts to deliver an overview of the research in this fast-growing field.

The objectives of this research are as follows. First, we intend to build an overview of the distribution of blockchain-related research by time, authors, journals, institutions, countries (regions), and areas in the blockchain academic community. Second, we probe the key research topics of blockchain study, for which purpose, we conduct keyword co-occurrence analysis. Third, we picture the intellectual structure of blockchain study based on co-citation analysis of articles and author co-citation analysis. Finally, we identify the direction for the evolution of blockchain study. We adopt Citespace to detect and visualize emerging trends in blockchain study. To achieve these targets, we posed the following research questions:

Q1: What is the distribution pattern of blockchain publications and citations over recent years? Q2: Which are the main international contributing countries (regions) and institutions in blockchain research, and the collaboration network among them? Q3: What are the characteristics of the authorship distribution pattern? Q4: What are the key blockchain subjects based on the number of publications? Q5: Which are the major journals or conferences for blockchain-related research? Q6: Which are the most influential papers in blockchain research based on the number of citations? Q7: Who are the most influential authors in blockchain research according to the author co-citation network? Q8: What are the research trends in blockchain? Q9: What are the most supportive funding agencies for blockchain research?

Our intended contributions in this research are twofold. First, it is an attempt of adopting co-citation analysis to provide comprehensive and up-to-date developing trends in the lasted hot area, blockchain. Second, this study depicts a state-of-the-art blockchain research development and gives enlightenment on the evolution of blockchain. The findings of this research will be illuminating for both academic researchers, entrepreneurs, as well as policymakers.

The rest of the article is organized as follows. The literature review mainly summarizes related work. The “Data and methodology” section describes the data source and methodological process. The “Results” section presents the main results based on the bibliometric analysis as well as statistical analysis. “Conclusions and implications” conclude this research provides answers to the aforementioned research questions and poses directions for further work.

2 Literature Review

Scientometric analysis, also known as bibliometric network visualization analysis has been widely adopted in numerous areas to identify and visualize the trends in certain fields. For instance, Bonilla, et al. analyzed the development of academic research in economics in Latin America based on a scientometric analysis [ 25 ] . Li, et al. conducted research on emerging trends in the business model study using co-citation analysis [ 26 ] . Gaviriamarin, et al. applied bibliometric analysis to analyze the publications on the Journal of Knowledge Management [ 27 ] .

Since the birth of bitcoin, as the foundation of which, blockchain has gained an increasing amount of attention in academic research and among practices. The research papers focus on the blockchain are quite abundant and are continuing to emerge. Among a host of papers, a few studies investigate the research trend of blockchain-based on a bibliometric analysis [ 22 , 23 , 28 , 29 , 30 ] .

Table 1 presents a summary of these bibliometric studies that summarized some findings on blockchain research, yet very few investigated the co-citation network and the evolution of popular topics in a timeline view. The number of papers these articles analyzed is relatively small, which may be because they used simple retrieval formula in searching blockchain-related articles, and it could pose a threat to bibliometric analysis. Therefore, this research aims to conduct a comprehensive analysis of the status of blockchain research, which is beneficial to future research and practices.

An overview of existing bibliometric studies on blockchain research

Note: NP = number of publications; WOS = Web of Science Core Collection; CNKI = China National Knowledge Infrastructure Databases; EI = EI Compendex, an engineering bibliographic database published by Elsevier; Scopus = Elsevier’s abstract and citation database.

3 Data and Methodology

This section elaborates steps to conduct a comprehensive bibliometric-based analysis: 1) data collection, 2) methodological process. The overall approach and methodology are shown in Figure 1 , the details could be seen as follows.

Research methodology

3.1 Data and Collection

As the leading database for science and literature, the Web of Science Core Collection has been widely used in bibliometrics analysis. It gives access to multidisciplinary information from over 18,000 high impact journals and over 180,000 conference proceedings, which allows for in-depth exploration of the complete network of citations in any field.

For the sake of acquiring enough articles that are relative to the blockchain, we select keywords from Wikipedia and industry information of blockchain, and some existing research literature [ 1 , 20 , 23 , 30 ] . Moreover, in consideration of that, there are a host of blockchain research papers in various fields, in fact, although some papers use keywords in abstract or the main body, blockchain is not the emphasis of the researches. Therefore, in order to get more accurate research results, we choose to conduct a title search instead of a topic search. Table 2 presents the retrieval results with different keywords in the titles, we find that among publications that are relative to the blockchain, the number of Proceeding Papers is the biggest, which is closely followed by articles, and a few reviews. Based on the comparison of five search results in Table 2 . In addition, for accuracy and comprehensiveness, we manually go through the abstract of all the papers form conducting a title search, and choose papers that are related to blockchain. Finally, a dataset with 2451 articles is used in the subsequent analysis.

The dataset we choose has good representativeness, although it may not completely cover all papers on the blockchain, it contains core papers, and in bibliometric analysis, core papers are enough to provide a holistic view for a comprehensive overview of blockchain research.

Blockchain research article characteristics by year from 2013 to 2019

Note: Document type include: Article(A), Proceedings Paper(P), Review(R); Timespan = 2013 ∼ 2019, download in May 31, 2019; Indexes = SCI-EXPANDED, SSCI, A&HCI, CPCI-S, CPCI-SSH, ESCI, CCR-EXPANDED, IC.

3.2 Methodological Process

The bibliometric approach has received increasing attention in many research domains. In this study, the methodological process mainly includes three methods: 1) descriptive statistical analysis, 2) article co-citation, author co-citation, and cluster analysis on co-cited articles; 3) time-zone analysis on co-cited keywords.

Descriptive statistical analysis displays an overall status of the research development in the target field, which mainly presents an overview by publication years, document types, the research area of published journals, number of citations, and in terms of most cited paper, influential author, institutions and countries. Co-citation analysis helps to identify the frequency of co-cited papers and authors and provides crucial insights into the intellectual structure of certain research fields [ 31 ] . Time-zone analysis helps to understand the flow of information and research trends in the target area [ 32 ] .

Various visualization tools have been designed and developed as computer software such as Citespace and VOSviewer. In this study, we use Citespace for co-citation analysis and timezone analysis, VOSviewer is adopted for social network analysis and visualization, we also apply other tools such as Excel and Tableau for basic statistical analysis and the visualization of the bibliometric results. Notably, in Citespace, core nodes are displayed as “citation tree-rings”, which contain abundant information of an article, for instance, the color of a citation ring denotes the year of corresponding citations, and the rule of colors in Citespace is the oldest in dark blue and newest in light orange with a spectrum of colors in between, the thickness of a ring is proportional to the number of citations in a time slice [ 33 ] . Figure 2 illustrates the details of the citation tree-rings. In addition, Citespace adopts a time-slicing mechanism to produce a synthesized network visualization [ 34 ] .

Citation tree-rings [ 33 ]

4.1 Distribution by Publication Year

Table 3 illustrates several characteristics of blockchain-related publications sorted by the year of publication. The annual number of articles and countries has been growing continuously since the proposing of Nakamoto’s paper in 2008 [ 1 ] , and the first blockchain research paper was published in 2013. By examining the published papers over time, there were only eight articles published in 2013. Afterward, with a continuous increase, a peak of 1,148 articles was published in 2018, and the number of publications is likely to grow ever since. Meanwhile, the annual number of countries taking part in blockchain research has also rapidly increased from 6 to 93 between 2013 and 2017, whereas the average number of Times Cited for single articles declined from 34.00 to 1.73 between 2013 and 2018. Over the observation period, 97 countries took part in the research on the blockchain with a sample of 44 in the H-index of our paper.

Statistical description of Blockchain research article from 2013 to 2019

Note: NP = number of publications; No.CO = number of countries; AV.TC = average number of Times Cited.

Figure 3 presents the cumulative numbers of published articles and citations from 2013 to 2019. There was a drastic increase in the number of papers published annually after 2016. As for the cumulative number of citations, there was no citation of blockchain literature before 2013, and 272 citations in 2013. By 2018, this number has grown over 10,000, which implies a widespread influence and attention of blockchain study in recent years.

Cumulative growth in blockchain publications and citations, 2013–2019

The exponential growth is a typical characteristic of the development of research fields [ 35 ] . The model can be expressed as:

where C is the cumulative number of articles or citations, Y is the publication or citation year, α , and β are parameters. In this study period, the cumulative articles and citations in the filed grow exponentially by R articles  2 = 0.9463 and R citations  2 = 0.8691 respectively. This shows that the research quantity curve of the blockchain is like an exponential function, which means the attention of academic circles on the blockchain has been increasing in recent years.

4.2 Distribution and International Collaboration Among Countries/Regions

A total of 97 countries/areas have participated in blockchain research during the observation period. Table 4 shows the number of articles for each country (region) contributing to publications. Remarkably, an article may be written by several authors from different countries/areas, therefore, the sum of articles published by each country is large than the total number of articles. As can be seen from Table 4 , the USA and China play leading roles amongst all countries/areas observed, with publications of 532 (20.94%) and 489 (19.24%) articles respectively, followed by the UK, which published 214 (8.42%) articles.

Blockchain research country (region) ranked by number of articles (top 25)

Note: NP = number of publications; No.TC = number of total Times Cited; AV.TC = average number of Times Cited; No.CA = number of Citing Articles.

From the perspective of citations, according to country/area distribution in Table 4 , we also find that USA-authored papers were cited by 1,810 papers with 3,709 (36.57%) citations, accounting for 36.57% of total citations. Meanwhile, articles from the USA also have a very high average number of citations per paper with a frequency of 6.97, which ranks third among the top 25 countries/ areas. Interestingly, the articles from Austria and Singapore appeared with the highest average number of citations per paper, with a frequency of 7.44 and 7.16 respectively, whereas the number of publications from these two countries was relatively low compared with the USA. The second was China, following the USA, papers were cited by 753 articles with 1,357 (13.38%) citations. Although the number of articles from China is close to the USA, the average number of citations per paper is lower with a frequency of 2.78. The subsequent countries include the UK, Germany, and Italy. The results indicate that the USA is the most influential country in blockchain.

International collaboration in science research is both a reality and a necessity [ 36 ] . A network consisting of nodes with the collaborating countries (regions) during the observation period is shown in Figure 4 . The network is created with the VOS viewer in which the thickness of the linking lines between two countries (regions) is directly proportional to their collaboration frequency. We can see from Figure 4 that the USA has the closest collaborative relationships with China, the UK, Australia, Germany, and Canada. China has the closest collaborative relationships with the USA, Australia, Singapore, UK, and South Korea. UK has the closest collaborative relationships with the USA, China, France, and Switzerland. Overall, based on the collaboration network, collaboration mainly emerges in highly productive countries (regions).

International collaboration network of the top 25 countries (territories), 2013–2019

4.3 Institution Distribution and Collaboration

A total of 2,190 institutions participated in blockchain-related research, and based on the number of publications, the top 25 of the most productive institutions are shown in Table 5 . Chinese Academy of Sciences had the highest number of publications with 43 papers, followed by the University of London with 42 papers, and Beijing University of Posts Telecommunications ranked third with 36 papers. The subsequent institutions included the University of California System and the Commonwealth Scientific Industrial Research Organization (CSIRO). In terms of the number of total Times Cited, Cornell University is cited most with 499 citations, and the average number of Times Cited is 20.79. Massachusetts Institute of Technology followed closely with 407 citations and with an average number of Times Cited of 22.61. The University of California System ranks third with 258 citations and an average number of Times Cited of 8.06. ETH Zurich ranked fourth with 257 citations and an average number of Times Cited of 10.28. It is notable that the National University of Singapore also had a high average number of Times Cited of 12.56. These results indicate that most of the influential institutions are mainly in the USA and Europe and Singapore. The number of publications from institutions in China is large, whereas few of the papers are highly recorded in average Times Cited. Papers from the National University of Defense Technology China took the highest of average Times Cited of 7.79.

Blockchain research country (territory) ranked by number of articles (top 25)

To further explore data, the top 186 institutions with at least 5 articles each are chosen for collaboration network analysis. The collaboration network map is shown in Figure 5 , the thickness of linking lines between two institutions is directly proportional to their collaboration frequency. As seen from the cooperation network in the Chinese Academy of Sciences, Cornell University, Commonwealth Scientific Industrial Research Organization (CSIRO), University of Sydney, and ETH Zurich cooperated widely with other institutions. This shows that collaboration between institutions may boost the research of blockchain which echoes with extant research that proposes with-institution collaboration and international collaboration may all contribute to article quality [ 37 ] .

Collaboration network for institutions, 2013–2019

4.4 Authorship Distribution

The total number of authors who contribute to the publications of blockchain is 5,862. Remarkably, an article may be written by several authors from different countries (regions) or institutions. Therefore, the total number of authors is bigger than the total number of articles. In fact, during the observation period, the average number of authors per paper is 2.4 articles. Reveals the distribution of the number of authors with different numbers of papers. As seen from the results, most of the authors had a tiny number of papers, i.e., among 5,862 authors, 4,808 authors have only one paper, 662 authors have two papers, and 213 authors have three papers.

According to the participation number of articles, the most productive author in the blockchain is Choo, Kim-Kwang Raymond from Univ Texas San Antonio, who took part in 14 articles in blockchain, followed by Marchesi, Michele from Univ of Cagliari, who took part in 13 articles related to blockchain. The third most productive author is Bouri, Elie from the Holy Spirit University of Kaslik, and David Roubaud from Montpellier Business School. Miller, Andrew, Shetty, Sachin, and Xu, Xiwei ranked fourth, who took part in 10 articles related to blockchain.

The distribution of number of author with different numbers of articles

Note: No.AU = number of author; No.AR = number of articles.

Figure 6 displays the collaboration network for authors. The thickness of the linking lines between the two authors is directly proportional to their collaboration frequency. As we can see from Figure 6 , it indicates the most productive authors cooperate widely with others.

Collaboration network for authors, 2013–2019

4.5 Distribution of Subject Categories

Table 7 presents the top 25 blockchain categories ranked in terms of the number of articles published. As can be seen from Table 7 , among the top 10 categories, six are related to the Computer Science field, which indicates that blockchain-related researches are more abundant in the field of Computer Science compared with other research fields. Besides, there are also publications in the category of Business & Economics with 385 records.

The top 25 blockchain categories ranked by the number of publications

Figure 7 illustrates the betweenness centrality network of papers of the above categories by using Citespace after being simplified with Minimum Spanning Tree network scaling, which remains the most prominent connections. We can see from Figure 7 , the centrality of Computer Science, Engineering Electrical Electronic, Telecommunications, Engineering, and Business & Economics are notable.

Categories involved in blockchain, 2013–2019

4.6 Journal Distribution

The research of blockchain is published in 1,206 journals (conferences), the top 25 journals (conferences) are displayed in Table 8 . Blockchain research papers are concentrated in these top journals (conferences) and with a concentration ratio of nearly 20%. The major blockchain research journals include Lecture Notes in Computer Science, IEEE Access, Economics Letters, Future Generation Computer Systems, and Finance Research Letters, with more than 20 articles in each one. Meanwhile, the major blockchain research conferences include IEEE International Conference on Hot Information-Centric Networking, International Conference on Parallel and Distributed Systems Proceedings, International Conference on New Technologies Mobility, and Security, and Financial Cryptography and Data Security, with at least 14 articles published in each of these.

The top 25 blockchain publication journals (conferences)

Note: NP = number of papers; No.TC = number of total Times Cited; Italic represents conference.

4.7 Intellectual Structure of Blockchain

Since the notion of co-citation was introduced, there are a host of researchers have adopted the visualization of co-citation relationships. The work is followed by White and Griffith [ 38 ] , who identified the intellectual structure of science, researches then broaden the unit of analysis from articles to authors [ 39 , 40 ] . There are two major types of co-citation analysis, namely, article cocitation analysis and author co-citation analysis, which are commonly adopted to visualize the intellectual structure of the research field. In this study, we explore the intellectual structure of blockchain by using both article co-citation analysis and author co-citation analysis. We apply Citespace to analyze and visualize the intellectual structure [ 41 ] .

In this study, mining spanning trees was adopted to present the patterns in the author cocitation network, a visualization of the network of author co-citation is demonstrated in Figure 8 . In the visualization of the co-citation network, pivot points are highlighted with a purple ring, and landmark nodes are identified with a large radius. From Figure 8 , there are six pivot nodes and landmark nodes: Nakamoto S, Buterin V, Eyal I, Wood G, Swan M, Christidis K. These authors truly played crucial roles during the development of blockchain research. Table 9 shows the ranking of author citation counts, as well as their prominent publications.

Network of author co-citation, 2013–2019

The top 15 co-cited author ranked by citation counts

Nakamoto S, as the creator of bitcoin, authored the bitcoin white paper, created and deployed bitcoin’s original reference implementation, is not surprised at the top of the co-citation count ranking, and has 1,202 citations in our dataset. Buterin V, a Russian-Canadian programmer, and writer primarily are known as a co-founder of ethereum and as a co-founder of Bitcoin Magazine, follows Nakamoto S, receives 257 citations. Eyal I, an assistant professor in technion, is a third of the ranking, with a representative article is “majority is not enough: Bitcoin mining is vulnerable”. Wood G, the ethereum founder, and free-trust technologist ranks fourth with 244 citations. The other core author with high citations includes Swan M, Christidis K, Bonneau J, Szabo N, Zyskind G, Castro M, and Meiklejohn S, with more than 150 citations of each person, and the typical publications of there are present in Table 9 .

To further investigate the features of the intellectual structure of blockchain research, we conducted an article co-citation analysis, using cluster mapping of co-citation articles networks to complete a visualization analysis of the evolution in the research field of blockchain. According to the article co-citation network, we adopted Citespace to divide the co-citation network into several clusters of co-cited articles. The visualization of clusters of co-cited articles is displayed in Figure 9 .

Clusters of co-cited articles, 2013–2019

As we mentioned earlier in the “Data and Methodology” section, the colors of citation rings and links are corresponding to the different time slices. Therefore, the deeper purple cluster (Cluster #1) is relatively old, and the prominent clusters (Cluster #0 and #2) are more recent. Cluster #0 is the youngest and Cluster #1 is the oldest. Cluster labels are identified based on burst terms extracted from titles, abstracts, keywords of bibliographic records [ 26 , 41 ] . Table 10 demonstrates six predominant clusters by the number of members in each cluster.

Results show that the research priorities of the clusters keep changing during the observation period. From the earlier time (Cluster # 1), bitcoin and bitcoin network are the major priorities of researchers, then some researchers changed the focuses onto cryptocurrency in blockchain research. Notably, more researchers are most interested in blockchain technology and public ledger recently.

According to the characteristics of pivot nodes and landmark nodes in the co-citation article network. The landmark and pivot nodes in co-citation articles are shown in Figure 10 , Five pivot nodes are Nakamoto S [ 1 ] , Wood G [ 44 ] , Kosba A [ 51 ] , Eyal I [ 12 ] and Maurer B [ 55 ] . The main landmark nodes are Christidis K [ 45 ] . Swan M [ 2 ] , Zyskind G [ 48 ] Nakamoto S [ 1 ] , Kosba A [ 51 ] , Notably, some nodes can be landmark and pivot at the same time.

Landmark and pivot nodes, 2013–2019

Summary of the largest 6 blockchain clusters

Details of the largest cluster (Cluster #0, top10)

Details of the largest cluster (Cluster #1, top10)

Details of the largest cluster (Cluster #2, top10)

As seen from Table 10 , Cluster #0 is the largest cluster, containing 36 nodes, for the sake of obtaining more information about these clusters, we explored the details of the largest clusters. Table 11 illustrates the details of the Cluster 0#.

We also explored Cluster #1 and #2 in more detail. Table 12 and Table 13 present the details of Cluster #1 and Cluster #2 respectively, it is notable that the most active citation in Cluster #1 is “bitcoin: A peer-to-peer electronic cash system”, and the most active citation in Cluster #2 is “bitcoin: Economics, technology, and governance”. The core members of Cluster #1 and Cluster #2 deliver milestones of blockchain research related to the bitcoin system and cryptocurrency.

Table 14 lists the first 10 most cited blockchain research articles indexed by the Web of Science. These articles are ranked according to the total number of citations during the observation period. Among these articles, the publication of “blockchains and smart contracts for the internet of things” by Christidis is identified as the most cited paper of 266 citations. The paper also has the highest average number of citations per year.

The top 10 cited blockchain articles

4.8 Keywords Co-Citation Analysis

According to Callon, et al. [ 77 ] co-word analysis is a useful way of examining the evolution of science. In our study, among 2,451 articles related to blockchain, we obtained 4,834 keywords, 594 keywords appeared 3 times, 315 keywords appeared 5 times, and 130 keywords appeared 10 times. Table 15 presents the most important keywords according to frequency. As seen, ‘blockchain’ ranks first with an occurrence frequency of 1,105, followed by ‘bitcoin’ of 606. The other high occurrence frequency keywords include: ‘cryptocurrency’, ‘smart contract’, and ‘iot’ (internet of thing).

The top 25 keywords ranked by frequency

For the sake of further exploration of the relation amongst the major keywords in blockchain research papers, we adopted the top 315 keywords with a frequency no less than 5 times for co-occurrence network analysis. The keywords co-occurrence network is illustrated in Figure 11 . In a co-occurrence network, the size of the node represents the frequency of the keywords co-occurrence with other keywords. The higher the co-occurrence frequency of the two keywords, the closer the relationship between them.

The keywords co-occurrence network, 2013–2019

We can see from Figure 11 , the size of blockchain and bitcoin are the largest among all keywords. This means, in general, blockchain and bitcoin have more chances to co-occurrence with other keywords. Besides, blockchain is closer with a smart contract, iot, Ethereum, security, internet, and privacy, whereas bitcoin is closer with digital currency and cryptocurrency.

Figure 12 displays the time-zone view of co-cited keywords, which puts nodes in order from left to right according to their years being published. The left-sided nodes were published in the last five years, and on the right-hand side, they were published in recent two years. Correspondingly, some pivot nodes of keywords are listed in the boxes. We hope to show the evolution of blockchain in general and the changes of focuses in blockchain study.

The time-zone view of co-cited keywords, 2013–2019

The results suggest that, in 2013, when blockchain research begins to surface, bitcoin dominated the blockchain research field. Reasonably, the bitcoin is the first cryptocurrency based on blockchain technology, and the influential essays include quantitative analysis of the full bitcoin transaction graph [ 54 ] ; a fistful of bitcoins: Characterizing payments among men with no

names [ 50 ] ; and bitcoin meets google trends and Wikipedia: Quantifying the relationship between phenomena of the internet era [ 69 ] . Afterward, as various altcoins appeared, cryptocurrency and digital currency are widely discussed in blockchain-related research. The high-citation article is Zerocash: Decentralized anonymous payments from bitcoin [ 74 ] and privacy, which is the prominent characteristic of cryptocurrency. In 2015, blockchain and smart contract become a hotspot, the core publications include blockchain: A blueprint for a new economy [ 2 ] ; decentralizing privacy: Using blockchain to protect personal data [ 48 ] ; at the same time, some researchers also focus on the volatility and mining of cryptocurrency. In 2016, a growing number of researchers focus on the internet of things. The most popular article is blockchains and smart contracts for the internet of things [ 45 ] . In 2017, distributed ledger and blockchain technology become a research focus point. From 2018 onward, research focus on the challenge, and the inefficiency of blockchain appear.

4.9 Funding Agencies of Blockchain-Related Research

Based on all 2451 funding sources we analyzed in this study, the National Natural Science Foundation of China (NSFC) has supported the biggest number of publications with 231 papers, followed by the National Key Research and Development Program of China, which supported the publication of 88 papers. Comparatively, the National Science Foundation of the USA has only supported 46 papers. It is remarkable that the “Ministry of Science and Technology Taiwan” supported 22 papers, which is more than the European Union. Table 16 illustrates the top 20 funding agencies for blockchain research ranked by the number of supported papers. The results indicate that China is one of the major investing countries in Blockchain research with the biggest number of supporting articles.

The top 20 funding agencies of blockchain-related research

5 Conclusions and Implications

5.1 conclusions.

This research comprehensively investigates blockchain-related publications based on the Web of Science Core Collection and provides a quick overview of blockchain research. In this study, a coherent comprehensive bibliometric evaluation framework is adopted to investigate the hot and promising blockchain domain. We outline the core development landscape of blockchain, including the distribution of publications over time, by authors, journals, categories, institutions, countries (territories), intellectual structure, and research trends in the blockchain academic community. Combining the results of statistical analysis and co-cited articles, authors, and keywords, we formulate the answers to the following research questions:

RQ1 What is the distribution pattern of blockchain publications and citations over recent years?

The published blockchain papers significantly increased since 2013, when the first blockchain paper was published. An increasing number of articles were published since. In 2018, 1,148 articles were published at the peak, and the number of publications is likely to continuously grow. As for the cumulative number of citations, there were only 272 citations in 2013. By 2018 this number has grown to more than 10,000, which implies a widespread influence and attention attracted by blockchain study in recent years.

RQ2 Which are the main international contributing countries (regions) and institutions in blockchain research, as well as collaboration networks among them?

A total of 97 countries (regions) participated in blockchain research during the observation period. USA and China play the leading roles among all countries (regions), with publications of 532 (20.94%) and 489 (19.24%) articles respectively, followed by the UK, Germany, Italy, and Australia. From the aspect of citations, USA-authored papers were cited by 1,810 papers with 3,709 (36.57%) citations, accounting for 36.57% of total citations. Articles from the USA also have a very high average number of citations per paper with a frequency of 6.97. Although the number of articles from China is close to the USA, the average number of citations per paper is lower with a frequency of 2.78. The results indicate that the USA is the most influential country in the field of blockchain.

A total of 2,190 institutions participated in blockchain-related research. Among them, the Chinese Academy of Sciences has the highest number of publications with 43 papers, followed by the University of London, Beijing University of Posts Telecommunications, University of California System, Commonwealth Scientific Industrial Research Organization (CSIRO), Beihang University, University of Texas System, ETH Zurich. In respect of the number of total Times Cited and the average number of Times Cited, Cornell University is cited the most with 499 citations, and the average number of Times Cited is 20.79. followed by the Massachusetts Institute of Technology, University of California System, and ETH Zurich. The number of publications forms institutions in China is large, whereas few papers own high average Times Cited.

In terms of collaboration networks among different institutions, we found that the Chinese Academy of Sciences, Cornell University, Commonwealth Scientific Industrial Research Organization (CSIRO), University of Sydney, and ETH Zurich cooperated widely with other institutions.

RQ3 What are the characteristics of the authorship distribution?

The total number of authors who contribute to the publications of blockchain is 5,862. the average number of authors per paper is 2.4. Among 5,862 authors, 4,808 authors have only one paper, 662 authors have two papers, and 213 authors have three papers. Based on the number of participated papers, the most productive author in the field of blockchain is Choo, Kim-Kwang Raymond from Univ Texas San Antonio, who participated in 14 articles in the field of blockchain, followed by Marchesi M, Bouri E, David R, Miller A, Shetty S and Xu X.

RQ4 What are the core blockchain subjects and journals based on the number of publications?

Blockchain-related researches are more abundant in the field of Computer Science compared with other categories. Other major fields include Engineering, Business & Economics, Telecommunications, and Business & Economics.

RQ5 What are the major journals or conferences for blockchain-related research?

The research of blockchain is published in 1,206 journals (conferences), the major blockchain research journals include Lecture Notes In Computer Science, IEEE Access, Economics Letters, Future Generation Computer Systems, and Finance Research Letters. Meanwhile, the major blockchain research conferences include IEEE International Conference on Hot Information-Centric Networking, International Conference on Parallel and Distributed Systems Proceedings, International Conference on New Technologies Mobility and Security, and Financial Cryptography and Data Security.

RQ6 What are the most influential papers in blockchain research based on the number of citations?

Ranked by the total number of citations during the observation period, the publication: “blockchains and smart contracts for the internet of things” by Christidis and Devetsikiotis [ 45 ] is identified as the most cited paper with 266 citations, which also has a highest average number of citation per year, followed by decentralizing privacy: Using blockchain to protect personal data [ 48 ] with 169 citations and 33.80 average number of citations per year.

According to the number of times co-cited, the top five influential publications are as follows: Bitcoin: A peer-to-peer electronic cash system [ 1 ] , A next-generation smart contract and decentralized application platform [ 42 ] , Majority is not enough: Bitcoin mining is vulnerable [ 12 ] , Ethereum: A secure decentralised generalised transaction ledger [ 44 ] , Blockchain: Blueprint for a new economy [ 2 ] .

RQ7 Who are the most influential authors in blockchain research according to the author co-citation network?

Some authors played a crucial role during the development of blockchain research, Nakamoto S, as the creator of Bitcoin, and the author of the bitcoin white paper, created and deployed bitcoin’s original reference, therefore is not surprised at the top of the co-citation count ranking and got 1,202 citations in our dataset. Buterin V, a Russian-Canadian, programmer, and writer, primarily known as a co-founder of Ethereum and as a co-founder of Bitcoin Magazine who follows Nakamoto S and receives 257 citations. Other core authors with high citations include Eyal I, Wood G, Swan M, Christidis K, Bonneau J, Szabo N, Zyskind G, Castro M, and Meiklejohn S.

According to co-cited articles clusters, the research priorities in blockchain-related research keep changing during the observation period. Bitcoin and bitcoin network are the main priorities of researchers, then some researchers changed to focus on cryptocurrency in blockchain research.

RQ8 What are the research trends of blockchain?

The research priorities in blockchain-related research evolve during the observation period. As early as 2013, when the research on blockchain first appears, bitcoin dominated the blockchain research field. Then only one year later, as various altcoins begin to appear, cryptocurrency and digital currency are widely discussed in blockchain-related research. In 2015, blockchain and smart contracts become a hotspot till 2016 when a growing body of researches begin to focus on the internet of things. In 2017, distributed ledger and blockchain technology become the research focal point. From 2018 onward, research focus on the challenge and inefficiency of blockchain.

RQ9 What are the most supportive funding agencies of blockchain research?

The most supportive funding agency of blockchain research is the National Natural Science Foundation of China (NSFC) which has supported the publication of 231 papers. The results indicate that China is one of the major investing countries in Blockchain research with the biggest number of supporting articles.

Given the potential power of blockchain, it is noticeable that governments, enterprises, and researchers all pay increasing attention to this field. The application of blockchain in various industries, the supervision of cryptocurrencies, the newly rising central bank digital currency and Libra, are becoming the central issues of the whole society.

In our research, we conducted a comprehensive exploration of blockchain-related research via a bibliometrics analysis, our results provide guidance and implications for academic research and practices. First, the findings present a holistic view of research in the blockchain domain which benefits researchers and practitioners wanting to quickly obtain a visualized overview of blockchain research. Second, according to our findings of the evolution and trends in blockchain research, researchers could better understand the development and status of blockchain, which is helpful in choosing valuable research topics, the distributed ledger, the discussions on the inefficiency and challenges of blockchain technology, the supervision of cryptocurrencies, the central bank digital currency are emerging research topics, which deserve more attention from the academic community.

5.2 Limitations and Future Work

As with any research, the design employed incorporates limitations that open avenues for future research. First, this study is based on 2,451 articles retrieved from the Web of Science of Core Collection, although the Web of Science of Core Collection is truly a powerful database for bibliometric analysis, we can’t ignore the limitation brought by a unique data source. Future research can deal with this limitation by merging the publications from other sources, for instance, Scopus, CNKI, as well as patent database and investment data of blockchain, and it could help to validate the conclusion. Second, we mainly adopt the frequency indicator to outline the state-of-the art of blockchain research, although the frequency is most commonly used in the bibliometric analysis, and we also used H-index, citation to improve our analysis, some other valuable indicators are ignored, such as sigma and between centrality, therefore, it’s beneficial to combine those indicators in future research. Besides, it should be noted that, in co-citation analysis, a paper should be published for a certain period before it is cited by enough authors [ 26 ] , the newest published papers may not include in co-citation analysis, it’s also an intrinsic drawback of bibliometric methods.

Supported by the National Natural Science Foundation of China (71872171), and the Open Project of Key

Laboratory of Big Data Mining and Knowledge Management, Chinese Academy of Sciences

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Journal and Issue

Articles in the same issue.

Blockchain in accounting research: current trends and emerging topics

Accounting, Auditing & Accountability Journal

ISSN : 0951-3574

Article publication date: 19 October 2021

Issue publication date: 22 August 2022

This paper provides a structured literature review of blockchain in accounting. The authors identify current trends, analyse and critique the key topics of research and discuss the future of this nascent field of inquiry.

Design/methodology/approach

This study’s analysis combined a structured literature review with citation analysis, topic modelling using a machine learning approach and a manual review of selected articles. The corpus comprised 153 academic papers from two ranked journal lists, the Association of Business Schools (ABS) and the Australian Business Deans Council (ABDC), and from the Social Science Research Network (SSRN). From this, the authors analysed and critiqued the current and future research trends in the four most predominant topics of research in blockchain for accounting.

Blockchain is not yet a mainstream accounting topic, and most of the current literature is normative. The four most commonly discussed areas of blockchain include the changing role of accountants; new challenges for auditors; opportunities and challenges of blockchain technology application; and the regulation of cryptoassets. While blockchain will likely be disruptive to accounting and auditing, there will still be a need for these roles. With the sheer volume of information that blockchain records, both professions may shift out of the back-office toward higher-profile advisory roles where accountants try to align competitive intelligence with business strategy, and auditors are called on ex ante to verify transactions and even whole ecosystems.

Research limitations/implications

The authors identify several challenges that will need to be examined in future research. Challenges include skilling up for a new paradigm, the logistical issues associated with managing and monitoring multiple parties all contributing to various public and private blockchains, and the pressing need for legal frameworks to regulate cryptoassets.

Practical implications

The possibilities that blockchain brings to information disclosure, fraud detection and overcoming the threat of shadow dealings in developing countries all contribute to the importance of further investigation into blockchain in accounting.

Originality/value

The authors’ structured literature review uniquely identifies critical research topics for developing future research directions related to blockchain in accounting.

• Literature review
• Machine-learning approach
• Future trends

Garanina, T. , Ranta, M. and Dumay, J. (2022), "Blockchain in accounting research: current trends and emerging topics", Accounting, Auditing & Accountability Journal , Vol. 35 No. 7, pp. 1507-1533. https://doi.org/10.1108/AAAJ-10-2020-4991

Emerald Publishing Limited

Copyright © 2021, Tatiana Garanina, Mikko Ranta and John Dumay

Published by Emerald Publishing Limited. This article is published under the Creative Commons Attribution (CC BY 4.0) licence. Anyone may reproduce, distribute, translate and create derivative works of this article (for both commercial and non-commercial purposes), subject to full attribution to the original publication and authors. The full terms of this licence may be seen at http://creativecommons.org/licences/by/4.0/legalcode

1. Introduction

Blockchain is a technology for storing and verifying transactional records that works by adding “blocks” of data to a ledger, called the blockchain, that is maintained across a network of peer-to-peer computers ( Coyne and McMickle, 2017 ). It is a potentially disruptive technology that has begun to have dramatic impacts on the business models and market structures of many industries ( Casey and Vigna, 2018 ), including accounting ( Bonsón and Bednárová, 2019 ; Deloitte, 2016 ). However, the wealth of information produced about blockchain can make it challenging for researchers to stay up-to-date with the latest developments ( Cai et al. , 2019 ; Linnenluecke et al. , 2020 ). In these circumstances, the role of a structured literature review (SLR) of emerging research of blockchain in accounting should be a helpful tool ( Cai et al. , 2019 ; Moro et al. , 2015 ).

There are published literature reviews on how blockchain might be applied in a wide variety of academic disciplines, including business and management ( Xu et al. , 2019 ), supply chains ( Wang et al. , 2019 ; Gurtu and Johny, 2019 ), FinTech ( Cai, 2018 ; Rabbani et al. , 2020 ), the Internet of things ( Conoscenti et al. , 2016 ), and even cities ( Shen and Pena-Mora, 2018 ) but there has only been one for accounting and it was limited to 16 articles and 20 industry reports/websites ( Schmitz and Leoni, 2019 ). Other authors have also proposed different ways of applying blockchain technology in accounting and auditing (e.g. Yu et al. , 2018 ; Kokina et al. , 2017 ; Faccia and Mosteanu, 2019 ; Bonsón and Bednárová, 2019 ), without offering a comprehensive overview. Similarly, Bonsón and Bednárová (2019 , p. 737) conclude that “blockchain is an under-explored phenomenon, [and] future research is necessary to obtain a full understanding of this emerging technology and its implications for the accounting and auditing sphere”.

What are the current major research trends and topics related to blockchain for accounting?

What is the focus and critique of the key research topics?

What are the future research trends related to blockchain in accounting?

The studies collected for the review were drawn from accounting journals indexed by the Association of Business Schools (ABS), the Australian Business Deans Council (ABDC) and the Social Science Research Network (SSRN). To help analyse the corpus, we enlist the support of machine learning as found in other studies ( Cai et al. , 2019 ; El-Haj et al. , 2019 ; Black et al. , 2020 ; Bentley et al. , 2018 ). From this, we contribute and provide a comprehensive picture and critique of the literature on blockchain in accounting. This includes an analysis of impact; an examination of the four most widely-examined topics, being the changing role of accountants, new challenges for auditors, the opportunities and challenges of blockchain technology application and the regulation of cryptoassets; and a discussion on areas for future research. Identifying emerging topics in the field is an important element in generating insights for future research ( Small et al. , 2014 ) and leading research innovations ( Cozzens et al. , 2010 ). Understanding what we have learnt and how blockchain technology is impacting accounting is of benefit to everyone connected to this area. It may also help to guide future research in this exciting area.

The remainder of the paper is as follows. In Section 2 , we discuss the concept of blockchain as an accounting technology. Section 3 outlines the methodology used for the review, followed by the results in Section 4 . The most representative articles are analysed in Section 5 , with future research directions discussed in Section 6 . Section 7 concludes the paper with the implications of this research for theory, practice and policy, along with the limitations of the study.

2. Blockchain in accounting

The main advantage of blockchain technology is that once a transaction is approved by the nodes in the network, it cannot be reversed or re-sequenced. The inability to modify a transaction is essential for the blockchain's integrity and ensures that all parties have accurate and identical records. Because blockchain is a distributed system, all changes to a ledger are transparent to all the members of a network.

Hence, if transparency is key, implementing blockchain may help to enhance a company's competitive advantage ( Deloitte, 2019 ), and it should certainly help to cultivate trust between market participants ( Yu et al. , 2018 ). In blockchain, the transaction verification process is not managed centrally. Rather, it involves all the computers in the network, so blockchain does not suffer from point of failure events. Nor can individuals collude to override controls or illicitly change or delete official accounting records ( Wang and Kogan, 2018 ). Companies that incorporate blockchain into their accounting systems therefore may reduce their risk of fraud ( Dai et al. , 2017 ). Using blockchain might also mean more transactions can be automated, less data are lost, transactions can be tracked better and users' needs throughout the process can be detected more easily ( Fullana and Ruiz, 2021 ; Bonsón and Bednárová, 2019 ). However, the primary and most valuable difference between traditional databases and blockchain is its novel solution to control whereby transactions cannot be deleted or changed ( Coyne and McMickle, 2017 ; Dai et al. , 2017 ).

Even though, for most industries, blockchain is still a new and not yet well-established technology, the World Economic Forum estimates that, by 2025, at least 10% of global gross domestic product (GDP) will rely on blockchains. And, by 2030, blockchains will have created $3.1tn in business value ( Panetta, 2018 ). It should therefore be unsurprising to consider that this revolution will start to change the nature of accounting and, in turn, the work of its practitioners and theorists (e.g. Yermack, 2017 ; Schmitz and Leoni, 2019 ; Yu et al. , 2018 ).

As such, a literature review on the status of blockchain in accounting is both topical and timely. The insights provided into this emerging technology will have implications for the accounting ecosystem–some beneficial, others challenging. Hopefully, this SLR will serve as a helpful baseline for practitioners, professionals and academics as we navigate the next potential revolution in accounting information systems.

3. Methodology

Massaro et al. (2016 , p. 2) characterise an SLR as “a method for studying a corpus of scholarly literature, to develop insights, critical reflections, future research paths and research questions”. The review process is conducted in several steps.

3.1 The research questions

RQ1. What are the major trends and topics developing within the research related to blockchain in accounting?

RQ2. What is the focus and critique of the key identified research topics?

RQ3. What are the future research trends related to blockchain in accounting?

3.2 Defining a set of articles for further analysis

Phase 1. We first composed a list of all accounting journals from the 2018 Chartered Association of Business Schools rankings (the ABS rankings), which amounted to 87 journals. We did the same for the 2019 Australian Business Deans Council Journal Quality List (the ABDC rankings). This netted 157 journals.

Phase 2. After removing duplicate journals covered in both ranking systems, we were left with 149 journals. In these, we looked for relevant papers published in the period Jan 2008 till June of 2020. We started our search in 2008 as this was when Satoshi Nakamoto first mentioned blockchain in his paper ( Nakamoto, 2008 ). Using the EBSCO, Scopus and Web of Science databases, we searched for any article with the key words “blockchain” or “distributed ledger technology” in the title or abstract. From 2,335 documents, we identified 112 papers that matched our criteria for publication source.

Phase 3. Massaro et al. (2016) outline that when undertaking an SLR, researchers should broaden the boundaries if there is very little published research. They also warn that what is published may already be out of date because of the long lead times involved in publishing academic articles. Massaro et al. (2016) bring clarity to “broadening the boundaries”, arguing that researchers need to search for sources other than academic journals, which may provide valuable insights into emerging research fields. The other sources might include conferences and open-source publishing platforms that offer researchers greater opportunities to disseminate their research to practice ( Massaro et al. , 2015 ).

Since blockchain is just such an emerging topic in the accounting literature ( Schmitz and Leoni, 2019 ; Bonsón and Bednárová, 2019 ; Yu et al. , 2018 ), we decided to add papers not yet published in the accounting journals but uploaded to the SSRN. SSRN is the leading social science and humanities repository and online community that provides “tomorrow's research today” ( Gordon, 2016 ). With more than 950,000 papers from over half a million authors in the e-library, SSRN offers an extensive pool of research ideas that can be tracked before publication to detect emerging research topics and current trends. These papers added an important contribution to our literature review. Here, we searched for “accounting” AND “blockchain” or “accounting AND distributed ledger” over the same period and found 68 papers, some of which overlapped with papers already retrieved. These were excluded, plus we also excluded any of the papers that had subsequently been published in a non-accounting journal or an accounting journal not ranked by ABS or ABDC. This left 41 additional articles to add to the corpus. Thus, our final sample comprised 153 papers on blockchain for accounting.

Portable Document Format  (PDF) versions of each of the articles were downloaded and stored in a Mendeley database with full referencing details. The sources and number of papers from each source are given in Table 1 .

3.3 Methods of analysis: Latent Dirichlet Allocation combined with manual analysis

In machine learning, there are many different text mining techniques, each designed to suit different types of data and different end purposes (see Wanner et al. , 2014 for a comprehensive review). We used a Latent Dirichlet Allocation (LDA) model, which is well-suited to providing a systematic and non-biased method of investigating a body of literature ( Cai et al. , 2019 ; El-Haj et al. , 2019 ; Black et al. , 2020 ; Bentley et al. , 2018 ; Fligstein et al. , 2017 ). El-Haj et al. (2019 , p. 266) explain that LDA leads to “wider generalizability, greater objectivity, improved replicability, enhanced statistical power, and scope for identifying ‘hidden’ linguistic features”. Research shows LDA to be a relevant and useful tool for working with both big and small literature corpora (e.g. Li, 2010 ; Asmussen and Møller, 2019 ; El-Haj et al. , 2019 ). Asmussen and Møller (2019 , p. 16) highlight that applying LDA to even small sets of papers provides “greater reliability than competing exploratory review methods, as the code can be rerun on the same papers, which will provide identical results”. For these reasons and more, the LDA method is currently one of the most commonly employed topic identification methods that does not simply rely on a static word frequency measure ( Blei et al. , 2003 ). Moreover, El-Haj et al. (2019 , p. 292) recommend employing machine learning methods and high-quality manual analysis in conjunction as they “represent complementary approaches to analyzing financial discourse”. We followed this advice, applying a hybrid approach that comprised LDA analysis, citation analysis and a manual review.

LDA allows us to explore latent relationships between terms and topics in a sample, identify the most representative articles for each topic and identify the trends within the topics. Using LDA helps us capture the idea of a document being composed of a (predetermined) number of topics that represent a probability distribution over a vocabulary. The number of topics is optimised using grid-search and coherence of topics ( Röder et al. , 2015 ). The model also supplies a list of articles that most strongly “belong” to each topic.

The text mining procedure is straightforward. In a Python environment ( www.python.org ), the articles are first converted from PDF documents into text files. The text is then converted into lower case, and all characters other than letters are removed. Next, stop words, such as the , and , but , if , or , are removed, and the remaining words are lemmatised into their dictionary word. Additionally, all words other than nouns are discarded. Finally, the documents are turned into a bag-of-words format and fed into the LDA model.

The results showed that the four topics with the highest marginal distribution accounted for more than half of the overall content of the sample. To test the validity and reliability of this result, we applied several other types of analysis suggested by researchers working with literature reviews. For example, Dumay and Cai (2014) and Jones and Alam (2019) argue that citation impact factors are increasingly important because they identify the most influential articles. Highly cited articles represent a “corpus of scholarly literature” that can help “develop insights, critical reflections, future research paths and research questions” ( Massaro et al. , 2016 , p. 767). To conduct a citation analysis, we use citation counts based on Google Scholar data, based on queries employing Harzing's Publish or Perish software as of 5 March 2021. This step also helped us validate that the papers and topics identified by the LDA analysis were among the most cited.

Although the LDA method helped us to identify past and current trends in the literature, Cai et al. (2019 , p. 710) contend that “the human researcher is potentially better equipped to evaluate future trends in the literature”. Hence, we also manually reviewed the 15 articles identified in the LDA analysis as the most representative of each topic. This review affirmed the results of the LDA analysis and gave us the opportunity to offer a critique and gain more insights while identifying future research directions.

This section provides answers to RQ1 : What are the current research trends and topics in blockchain for accounting?

Figure 1 demonstrates that the volume of articles on the topic is increasing annually. The first articles began to appear in 2015 and, by 2019, 4 articles had increased to 40 papers, with 35 already published just in the first half of 2020.

Of the top-ranked journals–either 4-star ABS or A* ABDC–only two have each published one paper on blockchain. This is a clear indication that the phenomenon has not yet fallen into mainstream research. Given its relatively recent appearance in the literature, this is not surprising. Additionally, most of the articles that have been published are normative in approach and look at the future applications of blockchain in accounting. From this, we can assume that, in future, more cases of blockchain applications in accounting practice will be researched. Once the literati start to read of blockchain having a real influence on the profession, we expect the number of papers published in the leading journals will increase.

4.1 Results of LDA analysis

The LDA analysis unearthed ten topics, which we needed to find appropriate names for. This we did in a two-step procedure. First, we looked at the terms listed against each topic, then we read the most representative articles for each group identified by the model. One author then developed a descriptive title, which was reviewed and perhaps modified before being approved by the remaining authors. The final topic names are listed in Table 2 , along with the 20 most important words for each topic and the marginal distribution of each topic.

As shown in Table 2 , the most widely analysed topics are: the changing role of accountants; new challenges for auditors; the opportunities and challenges of applying blockchain technology and the regulation of cryptoassets. These account for more than half of the papers. No other topic amounts to more than 10% of papers on its own. Figure 2 shows the representation of the different topics from 2016 to 2020. Since there were so few papers in 2015, we did not include this year in the chart.

Two of the most widely discussed topics–“the changing role of accountants” and “the new challenges for auditors”–only seem to be getting more popular. These two subjects account for the highest proportion of the articles. Although “new skills for teams” began to attract attention in 2019, papers on this topic still only account for a small portion of the sample. Interesting, even over such a short period, interest in some topics is already waning, e.g. “FinTech in banking”, “cryptocurrencies and cryptoassets”, and “blockchain and taxation”. With this in mind, and given the overwhelming interest in just a handful of topics, we focused the rest of our analysis on the top four topics.

4.2 Article impact

As mentioned in the methodology, we checked the validity and reliability of the topic results using citation analysis ( Dumay et al. , 2018 ). Table 3 shows the total citation counts for the top 10 articles as listed in Google Scholar citations (5 March 2021).

As shown, all but one of the ten most-cited articles were published in ranked accounting journals. In fact, three were published in the Journal of Emerging Technologies in Accounting. The one exception was found on SSRN. Additionally, the topics cited match the topics revealed by the LDA analysis, particularly new challenges for auditors, opportunities and challenges of blockchain applications, and the regulation of cryptoassets.

Dumay and Cai (2014 , p. 270) note that “One problem with determining the impact from citations alone is that older articles can accumulate more citations”. To overcome this problem and to identify emerging articles, in Table 4 , we also calculated the citations per year (CPY). Six articles are common to both rankings: Kim and Laskowski (2018) , Fanning and Centers (2016) , O'Leary (2017) , La Torre et al. (2018) , Kokina et al. (2017) , Issa et al. (2016) . This offers clear support for the results of the LDA analysis. Further, two of the articles were published in 2019 and are already in the top 10, which is a sign of just how strong the interest in blockchain technology is.

The results of Table 4 allow us to confirm our choice of the topics for further analysis. The top 10 papers with the highest citations per year belong to one of the four research topics that have the marginal distribution over 10% represented in Table 2 and account for more than a half of the overall distribution.

5. Key research topics: focus and critique

In this section, we answer RQ2 : What is the focus and critique of the key identified research topics?

While the LDA analysis revealed ten topics, much of the literature is focussed on four of these: the changing role of accountants, new challenges for auditors, opportunities and challenges of blockchain technology application and the regulation of cryptoassets. In the next sections, we analyse and critique these subject areas in more detail, paying attention to the papers that the model deemed to be strongly representative of each topic.

5.1 The changing role of accountants

Each of the papers on this topic discusses ideas about how the role of accountants and accounting treatments would change if/when blockchain becomes a mainstream technology. For example, several authors discuss the advantages of using blockchain to record transactions on a real-time basis ( Yermack, 2017 ; Dai and Vasarhelyi, 2017 ). Routine accounting data would be recorded permanently with a timestamp, preventing it from being altered ex-post, which Alles (2018) argues would further ensure the reliability of current accounting information systems. Real-time accounting would also reduce the potential opportunities for earnings management ( Yermack, 2017 ). Additionally, using blockchain means anyone can review all transactions, even those that may be suspicious or related to conflicts of interest. Irreversible transactions also mean accountants could not backdate sales or report depreciation expenses in future periods when they should be expensed immediately. As a tool for accuracy and transparency, blockchain places pressure on accountants to justify their accounting choices. It also creates a closer link between accounting and a company's responsibilities to its stakeholders and makes it more challenging for financially-distressed companies to hide their situation ( Smith, 2017 ).

Anyone could aggregate the firm's transactions into the form of an income statement and balance sheet at any time, and they would no longer need to rely on quarterly financial statements prepared by the firm.

We agree that blockchain will impact how accounting information is recorded, but we do not expect that accounting functions will disappear. Rather, accountants will likely retain some old functions, either as-is or modified to suit the new paradigm, and find they have an entirely new set of responsibilities, some of which will require them to develop new skills. For example, well-developed IT competencies may become a prerequisite for the accounting profession, at least in the interim period where firms are prepared to face the changes brought about by integrating blockchain ( Uwizeyemungu et al. , 2020 ; McGuigan and Ghio, 2019 ). That said, we do not think that such changes will happen overnight. It will take time before companies implement blockchain as a ‘foundational technology’, and any disruptions to the profession will take place over years ( Iansiti and Lakhani, 2017 , p. 4).

What could be an even more profound transformation of the profession is how the work of accountants might no longer involve only recording transactions. In future, accountants may need to provide professional judgements during the accounting process ( McGuigan and Ghio, 2019 ; Dai and Vasarhelyi, 2017 ). Even if blockchain takes over the recording and storing of basic accounting transactions, there will be a need to decide on the choice of the most appropriate amortisation and depreciation methods, the length of the useful life of property, plant and equipment, the accounting policies regarding accounting for inventories and fair-value accounting. Moreover, with an increase in the number of cryptoassets and initial coin offerings (ICOs) accountants may also need to develop their skills as advisors and consultants on how to report these kinds of assets and transactions. Further, if blockchain is implemented on a broad scale, accountants will not only have more information for planning and control, they may be required to synthesise it. This, too, will change the role of accountants, particularly management accountants. No longer relegated to the back office, accountants would likely take a much more prominent position as agents of intelligence, advising, communicating and attempting to closely link their firm's activities to strategic decision-making.

Blockchain may also lead to more disclosures of non-financial information, such as that related to sustainability and corporate social responsibility. The transparency of blockchain might prompt companies to do more explaining. They may wish to quantify and make visible “feel-good” information as a counterpart to the financial ( Smith, 2017 ). Additionally, blockchain provides opportunities to collect qualitative social and environmental data, which will continue to require assurance in the future. La Torre et al. (2018) argue that blockchain will generate an automatic assurance system for non-financial information that could substantially modify the current assurance paradigm. Therefore, blockchain may help accountants move away “from traditional accounting assumptions, such as monetary unit[s], economic entit[ies] and time periods, leading organisations more towards holistic views of their relations with the society” ( McGuigan and Ghio, 2019 , p. 800).

Lev and Gu (2016) argue that blockchain may reduce information asymmetry and lead to more effective decision-making. They put forward that the relevance of information disclosed only in financial statements is diminishing because of the growing importance of non-financial information and that blockchain's ability to store quantified non-financial information may see accountants working more closely with other decision-making bodies.

The disruptive potential of accounting technologies can only be fully realised with a similarly profound revolution in accounting thinking. Without an accompanying “mental revolution”, new technologies may result in incremental as opposed to step change.

5.2 New challenges for auditors

Blockchain may also disrupt the auditing profession. With the ability to autonomously execute some audit procedures based on blockchain, smart contracts will provide stakeholders with already partly verified information ( Rozario and Vasarhelyi, 2018 ). La Torre et al. (2018) claim that participants in the accounting ecosystem may act as auditors themselves. Accounting information may be verified by different actors thanks to the assurance abilities of blockchain and because companies can continuously share information. Moreover, there is the possibility to automate some external auditing functions over the blockchain to improve audit quality and narrow the expectation gap between auditors, financial statement users and regulatory bodies ( Rozario and Vasarhelyi, 2018 ). Some authors call for the appearance of a new brand of auditor that can offer attestation services for independent evaluations of blockchain controls ( Canelón et al. , 2019 ; Sheldon, 2019 ).

However, some researchers are not convinced that blockchain will dramatically impact the auditing profession. Rather, they suggest that auditing will take on new features and become more complicated ( Dai et al. , 2019 ; Issa et al. , 2016 ). Distributed public recording on the blockchain will allow real-time audits in many locations and organisations simultaneously ( Issa et al. , 2016 ). These authors argue that auditors will need improved skills to audit the data not only for one company but also for the whole accounting ecosystem.

… continuously collect data from the real world, create a variety of intelligent modules for real-time auditing, monitoring, fraud detection, etc., and thereby improve the effectiveness and efficiency of assurance services.

Blockchain will require auditors to gain new IT skills and technical knowledge as without an improved understanding of blockchain, they will not be able “to design efficient and effective audit processes, to collect accurate audit evidence, and to review the system for potential risks and frauds” ( Dai et al. , 2019 , p. 38). Of course, for blockchain technology to enable continuous auditing and for it to give auditors a better understanding of their clients' businesses, companies will need to record all transactions on the blockchain ( Schmitz and Leoni, 2019 ). After all, “real-time auditing” can only be delivered to the degree that transactions are recorded on the blockchain.

Auditors should be concerned about the risks of privacy breaches deriving not only from both external unauthorised access but also from accessing and using certain corporate and external data to perform audit activities; the latter being a task that needs to engage principles that go beyond legal prohibitions.

Blockchains do not provide a guarantee for transactions taking place in the real world. Even if they are recorded onto blockchains, transactions may still be fraudulent, illegal or unauthorised. Hence, given the need for auditors to detect and investigate transaction errors or fraud, the argument of auditors becoming obsolescent is not evident.

Essential roles for auditors in the future will be assuring the reliability, credibility and authorisation process of blockchain transactions.

Implementing blockchain may benefit most accountants and auditors, but it may be negatively perceived by those who work in the black economy, those who are keen on earnings management, and those who need to manipulate the appearance of illicit transactions. Therefore, we assume that automating data collection and storage using blockchain will not mean the auditing profession disappears. Rather, we see it evolving into a new role within companies and the ecosystem of blockchain accounting.

5.3 Opportunities and challenges of blockchain technology application

Papers on this topic are mostly written from the perspective of a company implementing blockchain. Opportunities range from improved efficiency, transparency and trust to the high potential of new business models and ecosystems that evolve due to blockchain. Challenges include potential risks related to blockchain implementation, the influence of context and a high demand for energy consumption.

Because blockchain eliminates the need to enter and reconcile information in multiple databases, efficiency gains are a key strength. Blockchain also saves time by increasing the speed of transactions, reducing human error and minimising fraud ( Kokina et al. , 2017 ; O'Leary, 2017 ). The use of smart contracts may also improve processes in a range of industries. Smart contracts on the blockchain execute when certain conditions are met without the need for trusted intermediaries to verify the fact ( Coyne and McMickle, 2017 ; Kokina et al. , 2017 ). There is already evidence to show how blockchain may reduce costs in the finance industry (e.g. Fanning and Centers, 2016 ; Kokina et al. , 2017 ).

One of the challenges for implementing blockchain is context ( Stratopoulos and Calderon, 2018 ). It is unlikely that small firms would want to make their transactions publicly available or that they would benefit from blockchain accounting as much as big companies. Distributed ledgers may not be attractive or even needed by every company, so there is a real need to ascertain exactly what the up and downsides of implementing blockchain are. As O'Leary (2019) observes, the opportunities for using blockchain may be limited by the desire and ability of all agents in the ecosystem to implement it. For example, some companies may wish to use a private blockchain, but we do not yet know how to accommodate multiple private blockchains with different levels of secrecy and different kinds of trading partners, some of whom may be members of a public blockchain ( O'Leary, 2019 ; Kim and Laskowski, 2018 ).

It is also important to understand all the advantages and disadvantages of joining a public or a private blockchain ( O'Leary, 2017 ). There are many different configurations of blockchain, e.g. peer-to-peer and public, cloud-based, private and these all need to be analysed before they can be soundly implemented in different settings. Further, those investigations must include analyses at the accounting, auditing and supply chain levels. For example, O'Leary (2017) argues that public blockchains are not the best approach to capturing accounting or supply chain transactions. Instead, he believes private and cloud-based blockchain configurations will dominate the corporate landscape. In a private blockchain, only a preselected number of nodes are authorised to use the ledger. Hence, not everyone has access to all company's data. Yet many researchers speak positively about how blockchain technology will mean provenance in the supply chain that is much more traceable ( Kim and Laskowski, 2018 ). In our opinion, it will be important for all the agents in the ecosystem to understand how blockchain provides similar benefits. For example, due to the potential risks of disclosing information, we assume that blockchain will have a more restrictive effect on business entities than non-profit organisations, because non-profits tend not to hold as many commercial secrets.

Moreover, Kokina et al. (2017) note that the scalability of blockchain is an issue from a technical perspective, as blockchain is computationally intensive and requires a lot of energy. This raises sustainability questions and may not be an issue that gets resolved until renewable energy accounts for most of our energy production ( Coyne and McMickle, 2017 ). Three further risks are often raised, each surrounding changing business processes ( Canelón et al. , 2019 ; Coyne and McMickle, 2017 ; Kokina et al. , 2017 ). The first relates to the centralisation of computing power, also called the “51% attack risk”, which can happen when most of the computing power in a blockchain's network is centralised. In this case, whoever controls that power can, with impunity, discard a valid link in the chain or substitute an invalid block for a valid one. The second risk is transaction malleability, which occurs when an attacker copies a transaction and modifies it to receive tokens (payment) then claims that no tokens were ever received. The third risk relates to flawed smart contracts that can hide malicious code or another contract with a weakness. This risk highlights the need for independent external auditors to approve transactions before the contract enters the blockchain. In short, the ability of blockchain to store records makes it a target for potential cyberattacks. Therefore, to ensure the security of information in a blockchain, there is a need to implement internal and cybersecurity controls that consider privacy preservation issues ( Chohan, 2017 ; Coyne and McMickle, 2017 ; O'Leary, 2017 ).

To gain real efficiencies in the use of blockchain or any technology, there is a need to reengineer, rather than just automate, existing processes. Unfortunately, many of the proposals for the use of blockchain are aimed at automating existing processes, typically in an approach to leverage the immutability and digitisation of paper, but generally do not propose or use changes in the processes.

Unless existing processes and systems are truly scrutinised for their potential to benefit from blockchain technology, the full range of opportunities that blockchain presents will not be realised. Blockchain will only become a “game-changer” if all parties involved in the accounting ecosystem are open to its potential.

5.4 Regulation of cryptoassets

The papers devoted to this topic analyse a variety of questions related to the regulation of cryptoassets (also called tokens), including cryptocurrencies and ICOs (e.g. Gurrea-Martínez and Remolina, 2018 ; Wiśniewska, 2018 ). These assets are not addressed by any accounting standards, that leads to challenges in their classification and measurement and reflects the lack of economic characteristics for a “standard” intangible asset ( Procházka, 2018 ) or a financial asset ( Smith et al. , 2019 ). There are several regulatory issues that need to be solved: classification of cryptoassets in accounting; the kinds of insolvency that affect buyers and sellers of tokens; and the regulation of potential money laundering via blockchain ( Pimentel et al. , 2019 ; Zhang et al. , 2021 ). Moreover, with the increased competitiveness of the market, questions related to data protection and data safety on the blockchain become extremely important for further regulation ( Cai, 2018 ).

The uncertainty linked to valuing cryptoassets is affecting the development of proper regulations, as this issue affects the fundamental qualitative aspects of financial accounting, such as relevance and faithful representation. Moreover, as highlighted in the Conceptual Framework for Financial Reporting , the principles of prudence, neutrality and conservatism continue to pose challenges for properly presenting cryptoassets in financial statements ( FRC, 2018 ; The Interpretations Committee, 2019 ).

There is no commonly shared point of view among researchers on the best way to regulate cryptoassets. Some say that they fit in with the existing accounting standards, while others state there is a need to develop a new regulatory framework that will decrease the probability of fraud ( Auer, 2019 ; Pimentel et al. , 2019 ). For example, there is a high demand for developing regulations for ICOs, cryptoassets that do not offer investors concrete products or services but provide an opportunity for capital gains from reselling cryptocurrencies in the future ( Zhang et al. , 2021 ). In December 2017, SEC Chairman Jay Clayton stated that ICOs are vulnerable to fraud and manipulation because there is less investor protection than in the stock market ( Clayton, 2017 ). We think that as the tokenisation of securities would be a useful tool in capital markets in the future (as already reflected by their fast development in Asian markets) and because ICOs and crowdsourced platforms represent a legitimate means of exchange in ecosystems, the regulatory issues need to be resolved to make this instrument available to wider markets participants ( Gurrea-Martínez and Remolina, 2018 ; Zhang et al. , 2021 ; Sixt and Himmer, 2019 ).

Currently, regulators monitor the field of cryptoassets on a case-by-case basis, but not to the extent that investors, or would-be-investors, could determine with certainty how cryptoassets may be treated ( Smith et al. , 2019 ). Nor are all market participants eager to treat cryptoassets as a security due to their volatility, making it difficult to ascertain an appropriate value to record for income statement and balance sheet purposes ( Smith et al. , 2019 ; Tan and Low, 2019 ). Finally, it is worth noting that financial accounting is characterised by accounting prudence and conservatism, which can lead to differences between a company's market and book value ( Dumay and Guthrie, 2019 ). As cryptoassets are often characterised as a potential future economic benefit, their acquisition may lead to even greater discrepancies between the market and book values of companies, especially in markets with optimistic valuations of intangible assets.

Thus, the uncertainty on measuring cryptoassets leads to the problems of comparability, verifiability, timeliness and understandability in financial accounting ( IASB, 2018 , p. 6). Therefore, in line with Smith et al. (2019 , p. 166), we conclude that for now, “this innovative technology has the potential to change internal management systems …; however, lack of regulation and information makes investment planning for cryptoassets complex and forbidding”. The divergence of crypto classifications means that worldwide regulation and availability of information on cryptoassets will be the most important factors for their spread. As a result, we see the need for a proactive regulatory framework rather than merely reacting to questions regarding the regulation and accountability of cryptoassets.

6. Future research directions

This section answers RQ3 : What are the future research trends related to blockchain in accounting?

The following views regarding the future research trends were framed by the insights in the previous section and reviewing the most representative papers for each topic.

6.1 The changing role of accountants

As discussed in Section 5.1 , most papers on the changing role of accountants are normative. They talk mainly about various assumptions over how blockchain may influence accounting. One of the main changes frequently discussed is how blockchain will change the way accountants collect information. Given this, we think the future will result in more case studies and practically-oriented papers that empirically test blockchain's impact on accounting ( Alles, 2018 ). According to Zhang et al. (2017) , new business reporting models, such as triple-entry accounting, will demand investigations into how blockchain strengthens or alters functions like valuations and contracting. Further, the monitoring role of accountants in managing information for the benefit of stakeholders will need to be established ( Zhang et al. , 2017 ). However, Alles (2018) warns that there is a danger of the “empirical takeover” effect when papers become empirically driven. Thus, there is a need to establish a solid theoretical and conceptual background for how blockchain will disrupt accountancy.

The role of management in implementing blockchain is very important. According to Jarvenpaa and Ives (1991 , p. 205), “Few nostrums have been prescribed so religiously and ignored as regularly as top management support in the development and implementation of IT.” A high degree of support for specific IT innovations is needed to ensure companies hold fast to a long-term vision and optimally manage their resources to see it through. At the same time, these innovations can create a favourable organisational climate that can overcome barriers and resistance to change ( Clohessy and Acton, 2019 ). Future research might therefore investigate the structure of management bodies and the role of top management in blockchain implementation.

Prior research points to a growing trend in the topic of new skills for teams when implementing blockchain and using this technology in day-to-day work ( Changati and Kansal, 2019 ). Fang and Hope (2021) indicate that blockchain is more effectively implemented in teams comprising accountants, managers and experienced analysts as opposed to teams consisting only of highly experienced analysts. We expect that blockchain will involve more multi-tasked teams with diverse knowledge and skills to generate additional synergies. Therefore, future research may analyse the characteristics of teams and government bodies that work better together for the most efficient implementation and decision-making using blockchain.

6.2 New challenges for auditors

In the realm of auditing, future research could explore how different types of blockchain (public, private and permissioned) could be used in accounting and Audit 4.0 to improve the quality of the data collected ( Dai et al. , 2019 ). The dilemma of adopting blockchain in accounting and auditing is in finding the right trade-off between information confidentiality and transparency. The simultaneous protection of data privacy and maintenance of data accuracy is an important area for future research. Further, the ways of creating effective smart audit contracts and smart reporting contracts should also be studied with a special focus on executing traces and enforceability ( Schmitz and Leoni, 2019 ).

More extensive analysis is also needed on the auditing ecosystems based on blockchain ( Smith, 2020 ). For example, if a client is a part of several blockchains, any engagement to audit or attest that information must include an examination of all associated blockchains. In the case of supply chains, cross-border payments, and transfers of intellectual capital, the chains–be they digital or physical in nature–can include dozens, if not hundreds, of organisations. How to conduct an effective and successful audit of such systems should attract the attention of researchers.

Additionally, more real cases will need to be explored to see how technology might disrupt the auditing community ( Marrone and Hazelton, 2019 ). Researchers might also address data protection issues as well as the new skills and competencies needed to remain relevant and add value ( Moll and Yigitbasioglu, 2019 ). Some, like Siew et al. (2020) , argue that, while digitising the validation process will reduce errors, and the immutability of the blockchain will minimise the opportunity to commit fraud, blockchain accounting does not guarantee that financial reports will be true and fair; the processes still need to be tested and the various accounting judgements still need to be reviewed. Moreover, blockchain will not resolve questions over issues like reconciling accounting standards. Hence, accountants will still need to be involved in the process ( Cai, 2018 ). Thus, many of the benefits and challenges of blockchain for auditing still need to be analysed.

6.3 Opportunities and challenges of blockchain technology application

A more fundamental area of future research is the role of financial intermediaries and how their role might change. In the future, we expect to see competition and cooperation among traditional and new intermediaries, and research needs to explore these phenomena to provide guidance to all participants such as incumbents, new entries and regulators ( Cai, 2018 ). The influence of blockchain on risk management and companies' performance indicators is another promising area for future research as there is a need to identify how stakeholders' value creation may be affected by implementing blockchain ( Cai, 2018 ). It would also be worth examining whether the response of managers towards blockchain varies in different industries ( Cao et al. , 2018 ). Burragoni (2017) argues that implementing blockchain in the finance industry might help overcome the threat of a shadow economy, given the improved transparency and legitimacy on offer, but this is an assumption that needs further justification.

Analysing the role of blockchain in changing business models in different industries is sure to be a topic of great interest to researchers ( Johannessen, 2013 ). The efficiency of new business models in comparison to traditional ones may also bring new insights for academics and practitioners. Researchers should test new business models in a market and evaluate transaction efficiency and the degree of novelty in the transaction's content, structure, steering, resource use, network effects and value creation for stakeholders. Researchers can analyse the efficiency of blockchain implementation in different areas and focus on “the benefits of the first-mover advantage” ( Karajovic et al. , 2019 , p. 322). In the future, it will be important to monitor the progress of the implementation of blockchain in different types of organisations ( Gietzmann and Grossetti, 2019 ).

Researchers should analyse how blockchain ecosystems evolve and are applied ( Benjaafar et al. , 2018 ). Blockchain enables real-time, verifiable and transparent accounting, making it reasonable to assume that accounting information systems will become ecosystems. In a data ecosystem that progressively integrates a nearly infinite set of initially disconnected data, the ability to integrate coherently and apply software agents will be of high importance. With an almost infinite supply of new data, novel methods of measuring business performance will inevitably emerge ( Cho et al. , 2019 ). Understanding how blockchain distributes the power of transaction verification and how data are stored and managed to prevent any unauthorised data changes in ecosystems are also key questions in need of investigation.

The challenges of blockchain regarding sustainability and environmental issues should also be a focus in future research. On the one hand, a distributed carbon ledger system based on blockchain technology will not only strengthen the corporate accounting system for carbon asset management but also will fit within existing market-based emissions trading schemes ( Tang and Tang, 2019 ). Blockchain will help integrate national emission trading schemes and corporate carbon asset management into a single synthesised mechanism, making it possible to analyse the overall efficiency of carbon trading markets in some great amount of detail. On the other hand, Nyumbayire (2017) points to environmental sustainability as an issue, explaining that the algorithms that run blockchain require a great deal of electricity. Moreover, as the technology grows, the algorithms become more complicated, and more time and energy are required to validate transactions. We argue that in the future, researchers should investigate the sustainability and environmental issues related to blockchain in more detail.

6.4 Regulation of cryptoassets

To date, the growth of blockchain technology has not led to the building of a corresponding regulatory framework. Thus, there are many questions that need to be resolved surrounding the legal and accounting frameworks for accounting, recognising and valuing cryptoassets. Further, when these frameworks are developed, they will need to be analysed. Researchers will also likely want to determine whether the standard-setting bodies have developed credible reporting conventions over the financial implications of cryptocurrency transactions ( Raiborn and Sivitanides, 2015 ; Tan and Low, 2019 ). Future research could explore whether blockchain has or will have a positive effect on the timeliness of disclosures; how financial reporting standards welcome new types of assets; and how the uncertainty associated with cryptoassets can be overcome.

Academics, together with practitioners, should work on specifying how these regulatory dimensions need to be developed, what type of disclosures are relevant to cryptocurrencies and how disclosure costs may further impact market uncertainty ( Cao et al. , 2018 ). Clarifying the regulatory framework will probably also lead to more ICOs, as initiators will be better prepared and be able to respond to uncertainty in blockchain policy by increasing their voluntary disclosures ( Zhang et al. , 2021 ; Gurrea-Martínez and Remolina, 2018 ). Research on the efficiency and effectiveness of ICOs will be of high interest in the future.

How cryptoassets and cryptocurrencies should be taxed is also open to question ( Ram, 2018 ). Once clarified, researchers will be able to study the taxation policies applicable to this new class of assets in detail. One related research question for the future involves whether blockchain-based instant tax allocation helps to decrease the cost of tax compliance for companies or not ( Karajovic et al. , 2019 ). As the role of external contexts and legal frameworks is highly important to blockchain development ( Allen et al. , 2020 ; Stratopoulos and Calderon, 2018 ), researchers may study the differences in blockchain implementation in environments that are (and are not) “crypto-friendly”.

7. Conclusion

Our aim with this paper was to define the key topics and trends, past, present and future, that concern researchers in blockchain for accounting. Our analysis systematically identified these topics by analysing 153 relevant papers. By combining machine-learning methods with more traditional approaches, we were able to draw a holistic picture of the critical advances and trends in the corpus of literature. The results indicate that the most widely discussed topics are the changing role of accountants, new challenges for auditors, the opportunities and challenges of blockchain technology application, and the regulation of cryptoassets.

This paper provides a compact snapshot of the state of blockchain papers in accounting research. The trends and identified research directions may help predict future citation impact and informed our suggestions for future research. They may also help journal editors decide on calls for special issues as interest in this topic grows.

7.1 Implications for academics

Our analysis reveals that more than two-thirds of the papers under review were published in journals, while less than a third represent works in progress uploaded to SSRN. The top accounting journals from the ABS and ABDC rankings appear to be resistant to the blockchain field of research, as they have published only a few papers devoted to the technology. This could be because those journals are less friendly towards phenomenon-based research ( Von Krogh et al. , 2012 ) than fundamental research or that the publication process takes much longer, and we will see more papers in the upcoming years. Another reason could be that most existing articles are normative and are looking at the future applications of blockchain. We may assume that, in the future, when there will be more cases examining the actual application of blockchain in accounting practices and real examples of the influence of blockchain on the accounting and auditing field, the number of papers in the leading journals may increase. For now, we observe that, with the blockchain landscape changing daily, and ideas and research needing to reach the target audience faster than the traditional journal route allows, researchers are turning to SSRN to share their tentative findings ( Holub and Johnson, 2017 ). We also observe that Australian scholarship is now leading the blockchain research in accounting, as more papers were published in journals included in the ABDC ranking compared to the ABS ranking. Moreover, Australian journals such as the Australian Accounting Review and Meditari Accounting Research are among the top tiers of those who welcome such research.

It will be important to monitor the progress in the take-up of blockchain in the future ( Bonsón et al. , 2019 ; Gietzmann and Grossetti, 2019 ; Bonsón and Bednárová, 2019 ). More papers applying machine learning techniques will help to gather information from reports, and web crawlers will be able to discover new aspects of how blockchain technologies have been implemented in practice. Combined with manual analysis, these data will help to chart new paths forward for researchers.

7.2 Implications for accounting practice

Even though we anticipate that blockchain will influence accounting and auditing, we do not assume they will be totally replaced. Most expect that these professions will be augmented rather than fully automated, and the need for accountants and auditors will not disappear ( Agnew, 2016 ; Marrone and Hazelton, 2019 ). There will still be a need for professional judgement, and, further, issues such as reconciliation are almost impossible to perform at the current stage of blockchain's development. In line with McGuigan and Ghio (2019) , we argue that accountants will not only have to understand the data on blockchain, they will also have to interpret and explain the implications of this information to management and other decision-makers. As a result, accountancy is likely to become a much more strategically oriented profession.

However, the skills required of accountants are likely to change, and there may be a need for fewer entry-level accountants ( Kokina and Davenport, 2017 ; Marrone and Hazelton, 2019 ). There may be a shift towards notions such as creativity, innovation, holistic thinking, complex decision-making and sense-making. The ability to adapt to keep pace with an increasingly evolving business environment and technological context will also be important. Addressing such changes in education through content and delivery is necessary to ensure that graduates have up-to-date and workplace-relevant knowledge and can keep up with global accreditation standards and professional qualifications ( Al-Htaybat et al. , 2018 ). Teams, management and government bodies implementing blockchain and making decisions based on data obtained from blockchain will also need new skills to adapt to the changing environment ( Pimentel et al. , 2019 ; Siew et al. , 2020 ). Therefore, we propose that universities and higher education institutions should change and improve the curriculum of accounting and finance programmes to help students develop the above-mentioned skills. It is essential to start making the changes now as current students will soon become accounting and auditing practitioners as well as managers working with blockchain and other disruptive technologies.

7.3 Implications for policy

The literature review reveals a pressing need for legal frameworks to govern blockchain technologies and regulate cryptoassets. Comprehensive work by regulators and policymakers may help implement and spread these technological innovations further, opening new sources of financing for companies. There is also a need to work on legal and taxation policies for tokens, bitcoins and other cryptocurrencies so that they become valuable tools and stable assets in capital markets. With the improved regulatory framework, we also propose that in the future governments may develop national cryptocurrencies, e.g. crypto-euros or crypto dollars, that will be easier and faster to use compared to existing currencies. A well-developed regulatory framework may help tokens become a legitimate means of exchange in ecosystems that will start growing in the future. Further work is required from accounting bodies to accept new types of digital assets and develop standards that will solve the issues related to their recognition, measurement and disclosure. In the future, the implementation of blockchain may also raise questions related to the regulation of social and environmental accounting that becomes possible with this technology. All this will help to improve transparency further and decrease information asymmetry in the market.

7.4 Limitations

This study has several limitations. First, the sample only covers the period till June 2020. Extending this timeline could be an option for future research. Second, other machine learning techniques could be applied while working with the corpus of literature. Although our LDA approach is much more advanced than mere word count or word cloud methods, it still models documents using a bag-of-words representation. A similar topic model using more advanced neural natural language processing (NLP) architectures like Bidirectional Encoder Representations from Transformers (BERT) ( Devlin et al. , 2018 ) or Generative Pre-trained Transformer 3 (GPT-3) ( Brown et al. , 2020 ) that also consider the context and semantics of words might result in different fields of inquiry or a more revealing combination of topics. Third, we included articles uploaded to the SSRN database as well as published articles in ranked journals. We are aware that the peer-review process is accepted as a proxy for the quality of published works, especially with respect to academic journal articles ( Hart, 1999 ; Massaro et al. , 2015 ). However, we believe that, given the speed of new knowledge development, especially in the areas of disruptive technologies like blockchain, papers from SSRN added an important contribution to the topics identified. Finally, the validity of the results can only be considered at the time of the analysis, as literature reviews “are not a panacea” ( Massaro et al. , 2015 , p. 546). They only identify the current state of the field, and they only offer pathways for future research directions at a particular point in time.

The number of articles per year

Publication trends of the topics

Frequency distribution of articles

List of topics

Top 10 articles by number of citations

The top 10 articles by CPY

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Blockchain Research Topics for PhD, Masters, and Undergrad

Whether you’re a PhD student or an undergrad, the blockchain research topics listed here will offer great insights into the blockchain technologies field. For those who have followed the events happening in the banking, investing, or cryptocurrency over the past one decade, the term blockchain could be familiar.

What is Blockchain?

A blockchain is a continuously expanding collection of digital records, known as blocks, which are connected together via encryption. Blockchains are designed to be immutable and resistant to data alteration. Communities, the decentralized Web, token economies, and worldwide peer-to-peer data transfers are all made possible by blockchain.

Blockchain technology is built on top of a number of different technologies.

A huge number of key criteria influence the success of a blockchain ecosystem. Layer 1 DLT systems like Bitcoin and Ethereum have accomplished a lot, but no one blockchain protocol can remove all of the inherent restrictions. For example, increasing throughput without necessarily jeopardizing security is quite challenging.

Layer 1 blockchain protocols that are secure and efficient must either solve important challenges at the protocol level or allow solutions at a higher level.

Blockchain is the record-keeping technology behind the infamous Bitcoin network. Most importantly, blockchain is a type of database. It differs from typical databases in how it stores information.

Blockchains store data in blocks. Those blocks are then chained to each other. Any new incoming data is stored into a fresh block.

Once a single block is filled with data it is chained onto the previous block, which makes the data chained together in chronological order.

Blockchains store different types of information. Today, storing a ledger for transactions seems to be the most common use of blockchains.

In the case of Bitcoin, blockchain helps in creating a decentralized process so that no single individual has control. Instead, all users have a collective control over their activities.

Without wasting time further, let’s dive into the topics about blockchain.

Blockchain research topics

Even though blockchain technology has seen some great progress in recent years, the field is still ripe for investigations. This section contains a list of chosen research topics , as well as information on current issues and latest events.

Research Topics on Bitcoin and other cryptocurrencies

• The unobvious risks of an unregulated global p2p currency
• Changes in people’s attitudes toward cryptocurrencies.
• How social media influences the prices of cryptocurrencies.
• How to Make Bitcoin a Better Currency
• Evaluating the scalability and security of bitcoin.
• Regulatory responses to cryptocurrencies in the global stage.
• Does cryptocurrency have a place in global economic development?
• The disruption, challenges and opportunities of cryptocurrencies.
• Optimal selfish cryptocurrency mining.
• An Empirical Analysis Leading to a Cost of Production Model for Valuing Bitcoin.
• Examination of the standards for identification on blockchain.
• Issues in designing community currencies based on blockchain.
• Empirical analysis of denial-of-service attacks in the cryptocurrency ecosystems.
• Investigating the potential significance of blockchain in improving transparency in electoral processes across developing democracies.
• Limitation of computational power to the implementation of blockchain technologies.
• Exploring inefficiencies associated with blockchain e.g. speed

Internet crime and security issues facing blockchain

Cryptocurrencies may promote crime and the trade of illegal goods.

For instance, the recent rush by users to obtain bitcoins has raised many questions about the cryptocurrency. There is a strong belief that bitcoin will, in the near future, unleash a great economic potential because it provides a borderless peer-to-peer democratic and self-regulating system.

Despite all these benefits identified in the article, the authors note that blockchain may promote a wide range of illegal activities such as the sale of illegal drugs, illegal weapons, assassinations, unlawful gambling, money laundering, and even outright theft.

Illegal use of blockchain scare away potential new users that otherwise would prevent the rapid growth of cyptoccurencies to surpass the traditional payment methods since no users with good intentions would want to associate with a currency that promotes such unlawful activities.

The following 10 blockchain research topics could be helpful while pursuing your PhD studies:

• The effects of bitcoin regulation on the reduction of drug trafficking.
• Anti-money laundering legislations to prevent, detect and prosecute cryptocurrency-driven money laundering.
• The ease of tracing hacked bitcoins.
• The mainstream adoption of blockchain technology in developing countries.
• Bitcoin mining vulnerability in open computer networks.
• Efforts to achieve full decentralization of blockchain networks in the United States.
• Relationship between metadata of transactions and respect for the privacy of blockchain users.
• Evaluation of current incentive mechanisms on- and off-chain.
• The valuation of different crypto-assets.
• Is it possible to achieve crypto-trading: the exchange of one cryptocurrency for another.
• Bitcoin mining acceleration and quantification of blockchain performance.

Topics on Applications of Blockchain in Banking and finance

Banks tend to be more skeptical about forming deals with bitcoin companies. This is one of the obstacles facing the uptake of bitcoin. 

As a result, a hot debate has been triggered whether bitcoin has the potential to become a dominant global currency or it will be wiped out in the next few years.

With the continued growth of the value of bitcoin cryptocurrency, some investors believe that digital currencies will dominate the future. However, bitcoin, a forerunner in becoming a dominant cryptocurrency is faced with several obstacles that must be addressed for it to assert its dominance in the financial world.

Here are a list of 10 blockchain research topics related to banking and finance:

• How has blockchain technology revolutionized banking in Asia?
• Effects of blockchains on the speed of cross-border payments.
• The skepticism of traditional banking institutions about forming partnerships with cryptocurrencies.
• Analysis of IBM’s Food Trust blockchain.
• Potential improvements in speed of banking transactions after integration of blockchain into business operations.
• Settlement and clearance in international stock trading using blockchain.
• Estimation of banking and insurance fee saved through the use of blockchain-based applications.
• The role of blockchain technology in streamlining paperwork and bureaucracy in trade finance.
• The impacts of government sanctions on the adoption of blockchain technologies in their trade finance.
• Tracking the popularity and financial gains associated cryptocurrency scams.

Our expert writer can come up with a new topic and produce a high quality, original paper for you.

• The application of cryptocurrencies in blockchain-based crowdfunding.
• How blockchain can lower the cost of meeting regulatory requirements for syndicated lending.
• Contributions of blockchain to transformation of accounting, bookkeeping and audit.
• Smart contracting . There has been significant development in this field, with the goal of identifying the main needs for smart contracts and establishing templates for their creation. In order to make smart contracts safer and more secure, additional research is needed in this field.

Blockchain research topics in Healthcare

In healthcare, the privacy of patients is important. Some personal information health records must remain the health provider’s secret.

To avoid privacy complaints and potential legal implications, some hospitals can apply blockchain technology to secure millions of health records.

Below are some of the blockchain research topics in healthcare that could be valuable for researchers:

• Secure storage of patient medical records by leveraging blockchain technology.
• The use of blockchain to fight drug counterfeiting in the pharmaceutical industry.
• The contribution of blockchain-timestamped protocols to improving the trustworthiness of medical science.
• The application of blockchain to medicine traceability across an individual country.
• How blockchain technologies can reduce health-related follow-up costs.

Final remarks

Blockchain seems to be the future. Its application in many sectors including banking and healthcare are inevitable.

In any case, researchers have identified an ever-rising tidal wave of blockchain powered technologies in finance that show its ability to disrupt the finance industry.

You still need help with blockchain dissertation topics? Call us or chat with our live agent today. We will be glad to work with you and help you prosper.

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Blockchain technology in healthcare: A systematic review

1 Department of Computer Science, National College of Business Administration & Economics Lahore, Multan, Pakistan

Hassaan Malik

2 Department of Computer Science, University of Management and Technology, Lahore, Pakistan

Umair Bashir

Aiesha ahmad, shafia riaz, maheen ilyas, wajahat anwaar bukhari, muhammad imran ali khan, associated data.

All relevant data are within the manuscript and its Supporting information files.

Blockchain technology (BCT) has emerged in the last decade and added a lot of interest in the healthcare sector. The purpose of this systematic literature review (SLR) is to explore the potential paradigm shift in healthcare utilizing BCT. The study is compiled by reviewing research articles published in nine well-reputed venues such as IEEE Xplore, ACM Digital Library, Springs Link, Scopus, Taylor & Francis, Science Direct, PsycINFO, Ovid Medline, and MDPI between January 2016 to August 2021. A total of 1,192 research studies were identified out of which 51 articles were selected based on inclusion criteria for this SLR that presents the modern information on the recent implications and gaps in the use of BCT for enhancing the healthcare procedures. According to the outcomes, BCT is being applied to design the novel and advanced interventions to enrich the current protocol of managing, distributing, and processing clinical records and personal medical information. BCT is enduring the conceptual development in the healthcare domain, where it has summed up the substantial elements through better and enhanced efficiency, technological innovation, access control, data privacy, and security. A framework is developed to address the probable field where future researchers can add considerable value, such as data protection, system architecture, and regulatory compliance. Finally, this SLR concludes that the upcoming research can support the pervasive implementation of BCT to address the critical dilemmas related to health diagnostics, enhancing the patient healthcare process in remote monitoring or emergencies, data integrity, and avoiding fraud.

Introduction

Healthcare is a system that includes 3 main components: (i) Main suppliers of services for medical treatment, For instance, doctors, nurses, technicians, and hospital administrations (ii) Emergency related services [ 1 – 4 ], and (iii) Health and health-oriented service users, specific patients. In the current study, to encourage, preserve or restore the health of beneficiaries, we examine the health maintenance to include technology-based remotely controlling services increased by constituent service providers [ 5 – 9 ]. In the medical field, every year, there are more security and privacy breaches, in 2017, more than 300 breaches were reported, and up to 37 million records were affected during 2010–2017 [ 10 , 11 ]. The growing digitization of medical care has advanced the acknowledgment of issues about secure storage, accessing of patients’ medical records, ownership, and medical data from associated sources [ 12 – 16 ]. Blockchain is recommended as a method of addressing critical issues faced by healthcare, for instance, protected sharing of health records and adherence to data privacy laws [ 17 – 19 ].

Blockchain is a particular type of database that can be managed by the network of authenticated members or nodes [ 13 ] and stores immutable information blocks that can be strongly exchanged without interference by third parties [ 10 ]. With cryptographic signatures and the use of consensus algorithms which are implemented as key enablers in their application, data is stored and registered [ 20 ]. The capability of preserving data is a major aim for using the BCT particularly in healthcare [ 21 ], which is subject to massive sharing and dissemination of a significant amount of data [ 7 ]. In different stages, the development of blockchain technology, as well as its application in various contexts, had been materialized. The first phase of blockchain development was focused on cryptocurrencies, while the second focused on the use of smart contracts in industries like real estate and finance [ 11 , 22 ]. The 3rd generation of evolution concentrated on employing blockchain in non-financial areas including government, culture [ 23 ], and healthcare space [ 22 , 24 ]. Also, powered by revolutionary technical features such as data immutability [ 25 ], with the introduction of artificial intelligence, blockchain technology is having its 4th generation of evolution [ 26 ]. This asserted diversity in Blockchain’s application spectrum can be attributed to its ability to build decentralized [ 27 ] and trustless transaction environments [ 28 ]. As blockchain can tackle serious issues, such as automated claim authentication [ 9 ] and public health management [ 29 ], the healthcare sector is a prime choice for the application of blockchain technology [ 30 – 32 ]. This technology allows patients to keep personal data and determine with whom this can be shared, thus resolving current data ownership, and sharing issues [ 28 , 33 ]. At the same time, it allows recorded data to be integrated, modified, shared safely, and retrieved on time by relevant authorities using consensus protocols [ 31 ]. This is a significant benefit of the use of this technology in the healthcare system, as existing procedures need third parties to store the data [ 10 ]. Finally, because of possible human error, blockchain could potentially add accountability to data management processes [ 34 ] further decreasing the risks of mishandling or misusing recorded data [ 31 ]. Given the optimistic connotations of the effects of blockchain on social and business change, in contrast to previously defined expectations, it appears to be a discussion regarding its basic and derived advantages. A recent study indicates that while organizations will make substantial investments in the future in adopting blockchain-based technology due to a widespread perception that the advantages could be over-hype, they will probably accept a cautiously pragmatic approach [ 35 ]. It can be said that this technology has yet to fulfill its expectations [ 36 ], a fact that can be due to the prevalent adoption of block chain, particularly about regulatory barriers, to certain challenges [ 31 ]. The general public and specific users, for instance, patients or physicians are not acquainted with the way blockchain works, the technological features, or its advantages for data processing is another significant obstacle in promulgating the implementation of blockchain [ 35 ]. Suggest that it may take a considerable time for this technology to establish all anticipated stages of business transformation mainly because of the organizational, social, and implementation challenges, for example, security issues or governance reasons [ 22 , 31 ]. This could also be exacerbated by general confusion regarding the use of blockchain regarding legal enforcement and regulations of the government. Current research focuses on supporting blockchain operational growth and speed-up its prevalence by overcoming these barriers.

However, previous studies have made little attempt to comprehensively summarize the existing knowledge by using SLRs [ 9 – 13 ]. For example, bibliometric techniques were used by [ 10 ] to provide a summary of blockchain research patterns and components related to the implementation of blockchain in the field of healthcare. In [ 9 ] the different blockchain platforms have been developed to deploy blockchain in healthcare. The study [ 11 ] addressed different examples of the implementation in the healthcare of blockchain technology, the problems, and their potential solutions. In diverse contexts where this technology was implemented [ 12 ], addressed design choices and tradeoffs made by the researchers. The research studies of [ 13 , 14 ] have discussed the Blockchain-based applications throughout numerous industries and addressed many contexts of use for this technology in a broad manner. Recently [ 14 ] reviewed 39 studies to present an overview on common channels and other areas where blockchain technology is utilized for healthcare enhancement. Although these systematic literature reviews have a contribution to the extent of knowledge, their emphasis has been mainly on synthesizing or delineating blockchain technology patterns and areas [ 10 , 11 , 13 , 14 , 16 ]. However, researchers will get benefit from a concentrated discussion on the implications of its adoption [ 15 ], along with concrete obstacles and areas for progress for advancing the field, due to the reach and diversity of previous blockchain studies [ 11 ]. Through assimilating existing information and describing focus areas that require considerable academic attention, review-based research will assist in meeting these needs [ 11 , 16 – 19 ]. As a result of this necessity, we perform an SLR on the blockchain technology application. This SLR presents a valuable overview of ongoing research, gaps in current knowledge, and future avenues of research as well. The contribution of this study is in two ways, this research adds to the emerging blockchain literature in healthcare. First regarding their implementation areas, restrictions, and recommendations, it offers an advanced and thematically ordered classification of previous literature. Second, we propose a synthesizing process according to the results of the SLR to detail possible topics that need academic attention to further update the existing body of literature.

The present study is organized as follows: In Section 2, we provide a thorough description of the research method utilized to search, screen, and select the literature. In Section 3, we present relevant review works that have been conducted in the field of health care using blockchain technology and discuss all the papers that have been selected, focusing on their main findings, and highlighting research gaps for future research. Finally, in Section 4we conclude this study.

Methodology

SLRs always provide a thorough understanding of literature as it presents a complete and systematized review meeting all standard protocols in it [ 18 , 37 – 39 ]. SLRs also help in the understanding of current information gaps and, as a result, the discovery of potential research avenues [ 19 ].

Research questions

We conduct this SLR by addressing the following research questions (RQs).

The purpose of this research question is to identify the number of research papers issued every year, the average citation received on research papers yearly, and academic contribution on the subject by Journals, publishing houses, and community.

The purpose of this question is to identify the contexts in which blockchain technology has shown significant outcomes in healthcare.

The motivation behind this question is to identify existing problems and issues of blockchain technology in the healthcare field based on results, limitations, and conclusions of previous research studies.

The purpose of this question is to identify growing gaps and prospects of the future research agenda

Research objectives

The research objectives (ROs) of the article herein presented are the following:

• RO1 : Establishing an archive of work that relates a wide topic about Blockchain in healthcare and offers an open dataset about Blockchain for all other researchers.
• RO2 : Identify a more focused set of studies that have used blockchain technology in healthcare applications.
• RO3 : Identify problems and constraints discussed in the healthcare field using blockchain technology.
• RO4 : Characterize existing solutions in the field of blockchain in healthcare and clarify the similarities and differences between them using a characterization framework.

Research strategy

Nine databases—IEEE Xplore, ACM Digital Library, Springs Link, Scopus, Taylor & Francis, Science Direct, PsycINFO, Ovid Medline, MDPI—are recognized by previous studies as standard data sources of research papers about health informatics [ 40 ]. Reviewed papers have been outlined for understanding the research status of applying blockchain in health care. For the right database search the three keyword combinations existed as—“blockchain and Healthcare”, or “medical Health” or Medical Management or Health Management. The above keywords were extracted from an article of previous literature i.e. SLRs) using similar keywords such as blockchain and medical healthcare.

Study selection

The selection process aimed to find the articles that are the most relevant to the objective of this SLR. If there was the same paper in more than one source, as per our research, it was considered only once. The content of the papers chosen for the final sample was evaluated [ 39 , 41 ] to make sure that the findings of the present SLR produced clear results and that is not biased. For reaching a consensus of final inclusion or exclusion, two of the researchers finalized the evaluation. After completing this, the discrepancies of individual assessments were addressed through discussion. A third author was engaged in analysis and debate in situations where the two writers did not find consensus. After the papers were found, the first move was to delete redundant titles and those which are not connected in scrutiny. The standards for inclusion were limited to the hunt for String, and a study conducted by at least one of the following criteria for exclusion (EC) is omitted:

Inclusion criteria (IC`s)

• IC1 : Studies are released any time on or before August 2021.
• IC2 : Studies are limited to the journal, conference, report, workshop, and symposium articles only.
• IC3 : Availability of complete texts in digital databases.
• IC4 : Proposed models or frameworks present.

Exclusion criteria (EC)

• EC1 : Exclude duplicated studies.
• EC2 : Eliminate preview, book chapters, magazines, thesis, monographs, and interview-based articles.
• EC3 : Exclude studies based on quality evaluation criteria.
• EC4 : Studies written in a language other than English.

The choice of papers was based on clear above discussed criteria for inclusion and exclusion. Below Fig 1 has been developed through the aspiration from the PRISMA diagram [ 42 ]. Fig 1 shows the study selection process.

Results and discussion

This section describes the outcomes related to the systematic study RQs discussed above. 51 research studies have been selected to illustrate the outcomes of each RQs. Publication and other selection biases are a potential threat to validity in all SLR and we cannot exclude the possibility that some research studies were missed resulting in reduced precision and the potential for bias. Therefore, we made significant efforts in finding all eligible research articles, and conference proceedings from different well-reputed databases and by contacting experts in the BCT area through social media platforms. We believe that our work provides a significant contribution to the role of blockchain technology in health care.

Selection results

Our search identified 1177 records, of which 1126 were screened as shown in Fig 1 . 51 research articles were included in this SLR. The list of selected papers with descriptions of the overall classification results are discussed below.

RQ1: What is the advanced profile used for the employment of blockchain in the healthcare domain?

This SLR addresses the achieved descriptive records about the number of articles that have been published each year, publication source, the average citation received on research papers yearly (see Table 1 ). To complete this SLR, we have examined published surveys, systematic literature review (SLR), systematic reviews (SR), and research papers related to blockchain in healthcare, and published in the field of blockchain from 2018 to 2021. The number of highest citation research articles with the most citations is shown in Table 1 .

Fig 2 demonstrates the number of articles published each year from 2018–2021. The four obvious outliers are existing from 2018 to 2021. In 2018, 24 articles were published, 16 articles were published in 2019, 9 articles were published in 2020 and 2 articles were published in 2021.

The authors of the reviewed articles were found to be affiliated with institutes located across 17 countries. Five countries, China (number of articles = 12), USA (number of articles = 6), South Korea (number of articles = 4), Brazil (number of articles = 3) and India (number of articles = 3), cumulatively represented 65% of the sample (see Fig 3 ).

In addition, the analysis of author indexed keywords conducted by using word cloud showed that the main emphasis of article related to “blockchain”, “technology”, “data”, “healthcare”, “sharing”, and “medical” which are graphically illustrated in Fig 4 .

RQ2: What are the major healthcare domains where blockchain technology has been implemented?

In this part, we will discuss a review of the fundamental principles of blockchain. BCT is used in medicine, especially in managing the information in healthcare that particularly is important in the healthcare area as this technology involves the sensitive data of patients. This sector is important to society because innovations in this field will enhance the quality of people’s life. Following this logic, the computation can help to mitigate the effects of certain problems in this field. Informatics, for example, helps in the automation of medical records by ensuring more reliable data sharing, log management, and other applications. One of the first and most popular blockchain applications in healthcare is the exchange of health records. Information related to health is difficult to disclose because it is labeled as confidential information and includes patients’ details. Among the key works in the literature that discuss this application of blockchain technology are: [ 85 , 86 ]. The characteristics of blockchain-based architectures for the sharing of electronic healthcare records can vary. The features of blockchain-based systems for the exchange of electronic healthcare records may vary. One of the most well-known structures in the literature is discussed in the work of Azaria et al. [ 86 ]. Several recent papers in the literature have cited this as a framework for the development of other similar architectures. Some of these systems are inspired by Azaria et al. [ 86 ] cited in [ 30 , 79 , 87 , 88 ]. Voting is a formal statement of an individual’s or a group’s opinion or choice, whether positive or negative. Traditional voting methods, on the other hand, are centralized and are known to have security and efficiency flaws. The study [ 89 ] examines blockchain-based voting systems in depth and categorizes them based on a variety of characteristics e.g., the types of blockchain used, the consensus approaches used, and the scale of participants. Artificial intelligence (AI) is now the core technology for a wide range of applications, from self-driving cars to smart cities. One of the most crucial pillars of social and economic stability is smart healthcare, which is an integral part of smart cities. The research study [ 90 ] focused on designing a human-in-the-loop-aided (HitL-aided) scheme to protect patient privacy in smart healthcare. Profile matching technology can facilitate the sharing of medical information across patients by matching similar symptom traits. However, because the symptom attributes are linked to sensitive information about patients, their privacy will be compromised during the IoMT matching process. To accomplish fine-grained profile matching, the study [ 91 ] provides a verifiable private set intersection scheme and used a re-encryption technique to preserve patients’ privacy. Technologically advanced countries are exploring or implementing smart homes, it is convenient but risky. Most of the existing solutions are generally based on a single-server architecture, which has limitations in terms of privacy, integrity, and confidentiality. While blockchain-based solutions may alleviate some of these problems, they still face some significant obstacles. Lin et al. [ 92 ] developed a revolutionary safe mutual authentication method for use in smart homes and other applications. MedRec will be the first sharing architecture to be discussed, which uses a blockchain-based system to store electronic medical records. The MedRec considers resolving issues as data access response time, interoperability, and increased data quality in healthcare research [ 86 ]. It is worth looking into the resources that were used to create MedRec’s architecture, since it implements a private P2P network (Permission block chain), as well as using Ethereum’s smart contract platform, to make it easier to monitor and track network state transitions. One of the MedRec architecture’s hallmarks is that it provides patients with a consulting agency that has records of their healthcare background, enabling them to remain informed about health decisions. Another difference is that they enable the standardization of health data since they are adaptable and provide open data standards in a variety of formats. This architecture takes a novel approach to the use of health data management systems by enhancing security and establishing a common language for data exchange for research purposes [ 86 ]. While Azaria et al. [ 86 ] also plan to perform experiments and analyses with a diverse community of users. In summary, MedRec is a realistic choice for exchanging healthcare information that can be used to combine patient care, hospital care, and physician care. As a consequence, the reported data can help to minimize discrepancies among different systems of hospitals. As stated by [ 85 ], the method introduces the topic of cloud computing, which could help in creating new architectures for sharing healthcare records via blockchain, resulting in safer and more secure healthcare systems for clinical use. The authors propose a cloud-based architecture that uses a blockchain-based data system to connect a network of communication nodes. The paper [ 85 ] shows how to handle the exchange of healthcare information using a blockchain architecture, which employs the principles of intelligent contracts and, immutable bookkeeping. The major roles of BCT in sharing health information, remote care with IoT, security, and privacy, and supply chain are depicted in Fig 5 .

The list of blockchain-based healthcare methods is discussed in Table 2 .

RQ3: What are the existing problems and constraints raised by the previous studies in the healthcare field using blockchain technology?

Even though blockchain is a multidisciplinary concept with challenges and limitations, it can be applied to a variety of areas [ 88 ]. Researchers in this field are working to overcome or mitigate the negative effects of these factors. The following are some of the problems (i.e. technological challenges) that blockchain technology faces when used in healthcare [ 22 , 88 , 97 , 98 ].

1) Throughput

If the number of transactions and nodes in the network grows, more checks will need to be performed, possibly causing a network bottleneck. When dealing with healthcare systems, high throughput is a challenge because unless there is fast access, it might adversely affect a diagnosis which could save someone’s life [ 64 ], correspondingly recognizing that the suggested framework focuses on identifying inconsistencies will possibly not perform well when datasets are unlabeled. Issues including specifications for continuous updates by the used system [ 59 ], keyword set size [ 75 ], network set-up and disk space needed based on the blockchain type, such as Ethereum software, employed to the framework can all affect a framework’s scalability and performance quality [ 25 , 99 ]. Similarly [ 48 ], suggests that integrating certain features into established systems, e.g. making global smart deals, can offset higher performance-related costs. Furthermore, a small number of studies have suggested that performance-related problems can be connected to the node management in a suggested system.

Validating a block takes about 10 minutes; this can be harmful to system security services since successful attacks may occur during that time. Healthcare networks are complex and should be accessed at all times, as any delay may negatively affect the analysis of an exam.

3) Security

When a party has control of 51 percent of the voting power, this can adversely affect the computing power of the network. This is a serious issue that needs to be addressed because a harmed healthcare system will lead to healthcare organizations losing their reputation.

4) Resource Consumption

Since the mining process consumes a lot of energy, using this technology could result in a significant loss of resources. Since multiple devices are required to track patients in a healthcare setting, energy costs are high; however, the use of blockchain may result in high computing and energy costs. Managing these expenses is a challenge for businesses.

5) Usability

Since these systems are so complicated, usability is a challenge as well to deal with. Additionally, an API must be developed (Application Programming Interface) Users would enjoy the user-friendly features. Since not all health practitioners have the same level of education, As IT professionals, we should be able to use frameworks that are easy and effective.

6) Centralization

Even though blockchain has a decentralized design, certain implementations tend to concentrate the miner, which decreases network stability. Because this central node is insecure and may be hacked, hostile attackers can get access to the data it holds [ 25 ].

It is common to suppose that the Bitcoin framework allows blockchain to make sure the privacy of its nodes. The results of [ 25 ], on the other hand, contradict this assumption. Furthermore, strategies to provide this functionality to blockchain-based systems are needed [ 25 ]. Due to privacy laws and regulations, blockchain-based systems have to conform to the General Data Protection Regulation (GDPR). Our research also indicates those users’ reservations about the safe and ethical utilization of data could be a major barrier to blockchain adoption in healthcare systems. The existing issues are primarily associated with blockchain technology’s technological limitations, such as the protection of individual nodes [ 53 ], the degree of safety permitted through cryptographic elements implemented with the system [ 70 ], besides the preservation of confidential data whereas requesters complete their computations [ 100 ]. However, certain research has drawn attention to more socially relevant issues regarding sharing of public data [ 73 ] and users’ confidence in governments [ 49 , 74 ]. Such issues may also be linked to the suggested framework protection from the perspective of users for example users’ management and misuse of permitted personal keys/codes [ 46 ].

8) Constraint

Prior studies have identified constraints, which can be divided into four categories. These dimensions mean that such constraints extend beyond technical boundaries (costs of designing, implementing blockchain systems, data analysis for system assessment, and framework constituent elements) to include certain social facets also such as trust in the administration, infrastructure of technology in a country.

This set of constraints is specifically concerned with the time, capital, and economic expenses of putting a system of blockchain into action. For example [ 50 ], discuss resource constraints in IoT, while [ 28 ] discuss the costs of arranging dispersed app in the deployment of blockchain. Additional expenses that have been established as constraints and limitations in previous research include the linear increase in protocol costs based on the characteristics and attributes of the entities involved, such as patients [ 54 ], increased operational overhead for the patient, and access latency for the requester [ 69 ], the exchange and implementation costs depend upon inconstant inputs in size and length of a string [ 67 ]. The issues related to time are further listed as one of the limitations, i.e. the spent time in finding smart contracts globally [ 48 ], increased time consumption [ 57 ], transmission timing [ 53 ], the time needed for the data receiver to seek the required data in shared storage [ 68 ], and higher overall execution time [ 21 ].

RQ4: What are the potential healthcare avenues that would benefit from blockchain technology implementation?

Blockchain consists of a sequence of blocks connected with cryptographic techniques. The immutability of this is one of the most attractive characteristics to many industries. The data that is added to the blockchain is irreversible, consequently, allowing for the creation of a consensus-based, verifiable, and accurate data ledger. That creates blockchain especially well-suited to tasks wherever integrity of data is critical; ProvChain [ 101 ], an infrastructure based on this technology in giving chain-of-custody to the database, is a functional example of this immutability. There are many blockchain implementations, including Bitcoin, a cryptocurrency token based on the blockchain; and Ethereum, a cryptocurrency token based on blockchain. Ethereum [ 102 ], a blockchain ledger with Turing-complete computer-generated device that allows smart contracts to implement code on this; and JP Morgan’s Juno [ 103 ], an Ethereum fork that uses the particular consensus mechanism called Quorum, along with several other blockchain implementations. The execution of blockchain varies due to ways in their consensus approaches. Bitcoin, for example, employs the HashCash [ 104 ] Proof-Of-Work algorithm, which is a deliberately slow system intended to avoid denial-of-service attacks. As a vote against the blockchain’s agreement, every Bitcoin miner authenticates this blockchain system by conducting that algorithm. Ethereum includes Ethash, which is an algorithm called Proof-of-work based on the Dagger-Hashimoto algorithm, as described in the Ethereum Yellow Paper [ 103 ]. However, shortly Ethereum is likely to advance in an algorithm named Casper. It will consider the excess requirement of energy in Proof-of-work [ 105 ]. The implementation of smart contracts separates Ethereum from Bitcoin. The smart contract is one of the snippets of code that run on each blockchain node. These are self-executing contracts in which all members of the blockchain are bound by the agreement. In the same way, as a standard contract does, they influence advantages, responsibilities, also punishments related to contract-related conduct. It could be utilized to model the HIPAA healthcare personal health information (PHI) workflow to satisfy audit and regulatory standards, likewise, done inside Patientory since they resemble conventional paper contracts and rules [ 106 ]. A new type of blockchain trust model, trust in the consortium, is also emerging. Microsoft recently released the Coco framework, which enables the creation of blockchain-agnostic consortiums [ 107 ]. Above mentioned models are based on a pre-defined group of trustworthy parties. It can be among various clinics or in the UK, NHS Trusts, third parties, and manufacturers of devices. By implementing smart contracts only on the hardware of trusted partners, without requiring miners, a consensus can be generated. It turned out in remarkably improved results, through a Coco-optimized blockchain case capable of processing 1600 transactions in a second, taking the blockchain system very close to the major payment processors. Coco also supports a variety of trusted execution environments, including Windows Virtual Secure Mode, Arm Trust Zone, and Intel Guard Extensions to name a few.

1) Clinical trials

Managing trial subject consent and clinical trials itself is an area in which blockchain can potentially improve the accountability, audit ability, and transparency of researchers and practitioners in the medical field. By keeping the unchangeable log of a patient’s approval, officials could control the standard of clinical trials easily, making sure it complies with informed consent regulations of the country. It is especially important because a forged informed consent form is one of the common types of clinical fraud. It involves falsifying patient consent and editing records, implying that authentication of trial subjects is essential for avoiding it. That kind of setup may be improved by implementing a smart contract system that stops clinicians to use the data of patients unless a key is issued by the end of an auditable process of smart contract that requires permission in each step in the trial, as proposed by Benchoufi, Porcher, and Ravaud. This procedure should also allow the patient’s consent to be revoked. Executing the clinical trial of blockchain consent log provides the subjects with data ownership while also having a trail of audit for regulators, medical professionals, and researchers. The role of BCT in clinical trials is graphically represented in Fig 6 .

2) Sharing the data

Sharing information is regarded as the most significant opportunity for improvement in healthcare; however, it too poses a significant challenge in privacy. Sharing the data using BCT is presented in Fig 7 . Powles and Hodson [ 108 ] use DeepMind’s case study teamwork with the Royal Free London NHS Foundation Trust to address the need for transparency in how patient data is being shared with third parties. Regardless of the good impact on diagnosis/treatment of patients by the product suite of Google, one of the significant issues addressed in the previous case study was a lack of patient consent. On the other hand, Sleep Apnea American Association, and IBM [ 109 ] were collaborating to solve major healthcare challenges to examine sleep apnea (with IBM’s Watson supercomputer at home) in thousands of Americans, with informed and clear patient consent. That was critical to implementing the national standard for interoperability in the healthcare system of IT. Which was emphasized by Wachter and Hafter through a white paper in UK NHS in comparison to the US healthcare sector that emphasized the significance of interoperability in permitting patient Electronic Health Records (EHRs) over various clinics, such as various trusts that do not maintain a separate system to get access on these records built by different vendors.

In a report of Harland Simon on a project justifying RFID tagging in NHS Cambridge shire, about 15% loss of assets annually, resulting in a substantial cost to repurchase the items that hospitals previously have. Furthermore, as per GE Healthcare [ 110 ] report, nurses spend an average of 21 minutes per shift searching for misplaced devices as stated by, defining any device under $5000 as consumable and to again purchase if any device is lost, suggesting significant cost in the sector. Published by Harland Simon, another study reported that [ 111 ], by adopting radio frequency identification (RFID) standards for tracking of medical devices, NHS Forth Valley in Scotland had saved nearly £400,000 in cost avoidance by not having to buy the important devices which would have been lost by the medical system. Tracking of Drugs has been a completely different issue than tracking of devices because a major concern is counterfeits of drugs here. According to WHO’s report, In the US up to 10% supply of Pharmaceutical products is counterfeit. In the United States, the Food and Drug Administration (FDA) recently approved the utilizing the RFID to track pharmaceuticals between the supply side to the patient. It enables the whole sequence kept supervised, to make sure that pharmaceuticals were purchased from a legitimate source. Pfizer was the first pharmaceutical company to use RFID “e-pedigree” to ensure that patients and doctors could trust the source and capabilities of their flagship medicine, Viagra, after identifying it as one of their most counterfeited drugs. Because of the use of low-cost passive RFID tags and barcodes, the system enabled the pharmacists and wholesalers to check the authenticity of their Viagra through a simple RFID scanner at a low rate than Pfizer.

3) Records of patients

Blockchain is having the potential to significantly disrupt health services and place data in the patient’s hand. The specific intriguing steps are in MedRec [ 86 ], which provides doctors and patients with an immutable log of a health record as shown in Fig 8 . That has a different approach to incentivize miners by providing access to anonymized data about health in exchange for network maintenance. MedRec maps Patient-Provider Relationships (PPRs) using Smart Contracts when the contract displays a reference list having relationships between nodes on the Blockchain-system. This too places PPRs in the patient’s hand, empowering them in accepting, rejecting, or modifying relations with health service providers for example doctors, insurers, and hospitals, etc. Blockchain-system allows for interoperability in the health system by providing a decentralized ledger of accepted facts in healthcare records to which all health service providers are having access. It implies that while user interfaces may differ, the central ledger would be the same across all service suppliers. A challenge that exists relates to the current state of health records across providers, which contain significant amounts of the same information under different identifiers that may not be linked. This causes replication, and as the blockchain system increases in size, it is reduced in performance. The level of data duplication in all records will necessitate replication to maintain a reasonably performant system with unique, anonymized identifiers to identify the patient in all kinds of service. Adopting the blockchain health record is a business challenge in and of itself. The important thing is that medical records will not start from zero because they would have to replace the current setup, and that is challenging. Furthermore, the sheer volume of data generated in the healthcare sector is ever-growing, with Kaiser Permanente estimated to have between 26 and 44 petabytes of data on its 9 million members from EHRs and other medical data in 2014. The data volume which is logged and referenced would mainly exacerbate the scalability issue.

4) Drug tracking

Another opportunity is tracking the drugs using a blockchain system as shown in Fig 9 , which takes advantage of its immutability in the development of tracking and a chain of custody from manufacturer to patient. Chronicled is a technology startup company that is working on its product, Discover, that develops a chain of custody model that shows the manufacturing place of a drug, the places it had been since then, and when it was disbursed to patients, hence reducing the pharmaceutical theft and fraud. That enables the health professionals in meeting existing standards of the pharmaceutical supply chain, along with focusing on interoperability among healthcare professionals. The Counterfeit Medicines Project has been launched by Hyperledger, the Open-Source Blockchain Working Group, to address the issue of counterfeits of medicines. The origins of counterfeit medicines would have been tracked and thus eliminated from the chain of supply. One benefit of tracking drugs by blockchain-system over conventional methods is the inherent decentralization of trust and authority in the technology’s principles; whereas chief authorities could have bribed or faked, it is much more difficult to bribe a consensus of those on the blockchain. As a result, an existing standard in pharmaceuticals tracking in industry, ePedigree, which already employs RFID and a traditional database, is transitioning to its blockchain application. If medicines/drugs could be tracked and developed at the point of manufacture using blockchain’s inherent anti-tampering capabilities, that will remove the counterfeited pharma products engaging in the supply chain.

5) Device tracking

Tracking of medical devices is one aspect of Block chain in disrupting healthcare, from manufacturing to decommissioning. The monetary benefit generated through tracking of assets is clear; NHS East Kent Hospital discovered 98 infusion pumps they had no idea they still owned across three sites as concluded through the case study of Harland Simon [ 111 ] in which active RFID trackers were implanted. Because of this single case study, they saved $147,000 at $1,500 per person. The use of blockchain in conjunction with this technology allows for an immutable ledger that not only shows the current location of the device, also the location of the lifecycle, along with the serial number, distributors, and the manufacturer linked with the device, assisting with regulatory compliance. Deloitte identified the competency among the potential game-changers for blockchain in the domain of healthcare in a white paper. According to an IBM study, 60 percent of government stakeholders in healthcare believed the integration of medical devices and asset management as the most likely area of disturbance in industry. The blockchain-based system has various advantages above conventional products of location tracking. This immutability and tamper-proof properties of the Blockchain are the most obvious. This prevents a malicious user from changing or deleting a device’s location history. This is especially important given that theft of devices and shrinkage has been a major issue in the United States and the United Kingdom. This immutability, in addition to preventing traditional theft, also protect devices from being lost and reordered, that have incurred high cost in terms of both actual equipment cost and care provided. The setup must not add significantly to the workload of staff, nurses, or workers because that requires tapping the device only using a mobile phone and further entering the device location. Whereas the use of blockchain on the Internet of Things (IoT) is still in its early stages, Huh states a method to communicate the devices using an Ethereum blockchain and public key system of RSA. Likewise, the device while it stores on blockchain its public key also stores the associated private key on the device.

This study aimed to conduct an organized analysis of previous literature about the employment blockchain in healthcare for a better understanding of their current and probable state. The four key research problems are defined for this reason. RQ1 was presented with summing up top writers, publishers, publication houses, and designs of publication patterns of this subject. Furthermore, it included an existing outline of research about employing blockchain in the healthcare space. The comprehensive description of the reviewed articles is discussed in Table 3 . RQ2 was designed to help researchers better understand how blockchain can be used, it is responded by defining particular themes and sub-themes that reflect key aspects in employing blockchain in this sector. RQ3 further discussed its shortcomings and obstacles that previous researchers had encountered. We were able to recognize the research gap in the existing literature and responded to this question by summarizing its main research themes and existing limitations. RQ4 concentrated on the key aspects where future investigation can provide valuable insight. The fourth research question is addressed by combining findings through emerging differences, shortcomings, and previously proposed guidelines.

Conceptual evolution

According to the findings of the study, research in healthcare’s blockchain was largely focused on enhancing more creating new ideas and concepts that help researchers to derive multi-domain [ 59 ] also practicable blockchain in healthcare implementations. The viability of employment [ 99 ] is being established and evaluated across three sub-themes of research: design creation, applications on benefit-based, and developing predictive competencies.

Concept development

The findings of the analysis indicate that new proofs and algorithms have received a lot of attention, such as proof of data primitiveness [ 62 , 112 ], proof of familiarity [ 74 ], and simpler workload for proof of work; [ 54 ]. Studies have also focused on testing new variables and components in architecture systems, as well as improving frameworks that enable blockchain execution by including them. Consider cryptosystems based on attribute [ 72 ], approach the Stackelberg game [ 63 ], sibling intractable functions [ 70 ], and homomorphic computations for more efficient frameworks [ 77 ]. Further [ 113 ], suggested a new scheme (BBDS) based on blockchain to protect data transactions and maintain privacy [ 57 ]. Used fog computing estimation efficiency as well as reliable models for human pursuit acknowledgment to support remote e-health controlling [ 51 ]. To eliminate a single point of failure, they are focused on incorporating several time sources into their technique. Finally, this research has centered on how to boost the efficiency of already established algorithms and structures based on the blockchain.

Benefit-based application

Blockchain has been used in healthcare research to extract concrete benefits by identifying and testing new technology avenues. It involves work in upgrading the technical advantages of employing blockchains, such as advanced image processing [ 60 ], effective behavior recognition [ 57 ], and Internet-of-Things synchronization (IoT) devices [ 51 ]. Furthermore, the majority of studies in this category have centered on the use of blockchain technology to establish specific benefits of healthcare, e.g. mutual decision making in the medical field [ 74 ]. Blockchain adoption, for example, is being suggested to have positive implications while managing clinical trials [ 73 ], DNA data transmission [ 61 ], preventive healthcare, biomarker growth, and discovery of drugs are all examples of remote patient monitoring [ 50 , 53 , 64 ].

Advancing decentralization

Existing research is also considering promoting key advantages of blockchain technology throughout healthcare environments for encouraging justice and also efficient decentralization [ 76 , 114 ]. For instance [ 63 ], produced an efficient framework for promoting maximization of revenue maximization along with fair decentralized trade, considering that [ 48 ] stated the need for trade-offs for mining benefits. Researchers in previous literature already described blockchain’s prospects in developing transparency in exchanging the data [ 56 ], such as utilizing upright client roles [ 21 , 30 ]. By doing this, we can say that previous research about the increasing use of blockchain-based technology in the medical space is focused on spreading decentralization along with its related advantages.

Advancement in technology

Current studies have contributed substantial progress in terms of advancement and refinement of blockchain for the development of targeted deployment, particularly in the healthcare space. We suggested previous research that is classified in this theme be directed regarding the three main topical issues based on our review:

Developing intelligent healthcare ecosystems

The introduction of blockchain technology programs into healthcare environments has piqued the interest of some academics [ 45 ]. Such integrations can pave the way for the development of intelligent healthcare systems [ 100 ]. For example [ 47 ], argues that blockchain adoption will aid in the development of a more efficient e-health ecosystem. Prior research has also suggested frameworks for developing blockchain-based e-health [ 56 ] and telemedical information systems [ 33 ], which could help healthcare providers, expand the scope of their services in the future.

Improvements to the blockchain architecture on a technical level

The majority of this field’s study has concentrated on improving the efficiency of architectures and developed systems by technological improvements for example utilizing smaller data block sizes [ 74 ] and reducing transaction propagation delay [ 68 , 74 ]. Some attention has also been given to problems that have previously been described as possible roadblocks to the successful implementation of blockchain architectures. Memory and CPU specifications [ 77 ], as well as accurate node recognition, are among the problems considered in research, grouped under this theme [ 71 ]. The efficacy of potential solutions to the above problems has been illustrated in several cases by network and algorithm comparison studies [ 21 , 30 , 74 ]. However, we believe that this theme will continue to progress in the future, necessitating a parallel emphasis on comparative analyses to determine the most powerful networks and algorithms.

Building predictive capabilities

A similar pattern can be seen in blockchain technology’s use in healthcare as it enters the fourth step in development with the rising integration of AI [ 26 ]. IoT [ 50 ], sensors [ 47 ], wireless body area networks [ 53 , 64 ], big data [ 49 ], edge computing [ 76 ], and cloud technology have all recently been incorporated through blockchain-based device architecture [ 59 ]. Researchers are using such technologies to help them develop systems based on blockchain having predictive capacities for enhancing medical information systems and diagnostics [ 61 , 75 ]. Prescription fraud avoidance [ 47 ], verifiable data generation [ 77 ], and automatic claim resolution [ 47 ] have all been investigated previously using such frameworks [ 72 ]. Furthermore, studies have centered on using blockchain-based technology in supporting providers of health care services with other tasks, e.g data collection on population-level [ 46 ] and user identity description [ 28 ].

Enhancement of efficiency

Several researchers in previous literature have attempted to determine how blockchain-based implementation would improve the efficiency of healthcare processes [ 34 , 59 , 79 , 82 ]. According to this study, scholars’ attention has been drawn to two facets of performance improvement: structures and processes.

Prior research has focused on improving the efficiency of technological aspects of the processes that are needed to run a blockchain-based healthcare system. Prior research has also focused on developing systems for timely alerts [ 72 ] and adverse event reporting [ 73 ]. Some research has centered on increasing the computational processes efficiency [ 57 ] and thorough evaluation of suggested architectures [ 60 ] to ensure that its architecture gives far efficient processing as compared to conventional architectures [ 71 ]. Furthermore, studies have proposed changes in blockchain systems to resolve the alleged risks related to time management, data management, and managing related costs. For example, reviewed research has established mechanisms for reducing the cost of implementation after setting up initially [ 74 ], lowering storage costs [ 65 ], and making maintenance and storing files of any size is easier [ 62 , 112 ].

According to our analysis of the current literature, several steps have been applied to enhance the blockchain-based healthcare framework holistically. For example, research has focused on improving system interoperability [ 27 , 49 ], managing inter-institutional access rights [ 63 , 99 ], and data management [ 28 , 46 , 63 , 64 , 99 ]. Enhancing machine scalability [ 113 ] and efficiency have also received scholarly attention [ 60 , 65 ]. Researchers have concentrated their efforts on designing integrated service-oriented architectures [ 56 ] and enhancing the generalizability and flexibility of blockchain systems that have been implemented [ 21 , 27 , 30 ].

Management of data

According to the results, we can conclude that managing the data and medical records is getting more scholarly attention. Existing research has endorsed the blockchain’s utilization for medical data management [ 27 , 48 , 54 , 55 , 69 , 70 , 99 , 115 ]. Furthermore, by integrating heterogeneous forms of data [ 27 , 69 , 100 ], blockchain can aid in the development of an application system of information to manage such PHRs [ 59 , 64 ]. We define three main aspects of current research in this field based on the SLR.

Data privacy

Previous research about data security implications of this technology in medical care has focused on handling the privacy of data by maintaining permitted access to the data. According to the study, access control management [ 76 ] has gotten a lot of attention [ 45 , 46 ]. Because of the requirement of protecting the privacy of confidential data by greater transparency, access control, and immutability, this problem is particularly important in healthcare [ 55 ]. Prior research has developed a framework based on blockchain to guarantee the delivery of effective services [ 115 ], user-centric [ 114 ], and access to patient PHRs and other medical data that is safe and encrypted in response to this vital need e.g. [ 45 , 50 , 54 ].

Data protection

Another main concern discussed in studies on the blockchain aspects of data management in healthcare is the avoidance of unauthorized access and the preservation of data confidentiality to ensure data safety. The majority of the studies that were examined focused on preventing unauthorized access [ 66 ] and preventing eavesdropping [ 71 ]. Several methods have been proposed to achieve this aim, including efficient authentication [ 65 ], biometric authentication [ 49 ], user verification [ 55 ], and the use of dual signatures [ 63 ].

Data handling

Prior research has addressed the need for legally and legally compliant collection, sharing, and controlling of healthcare data to some extent. According to our findings, few research studies have recognized the importance of monitoring enforcement [ 100 ], let alone the criteria and targets for compliance [ 63 , 67 , 75 ]. However, the importance of data integrity has received a lot of attention [ 56 , 69 , 70 ]. Prior research has looked at issues like authentic data mobilization [ 46 , 77 ], double storage expenditure [ 68 ], and eternal data protection [ 68 , 112 , 116 , 117 ]. Along with the growing inter-institutional adoption of blockchain, researchers have transformed their attention to the issue of storing and maintaining sensitive data [ 67 ] from a variety of sources, including medical devices [ 52 ] and health insurance [ 77 ]. A few studies have concentrated on the assistance of cross-institutional sharing of data [ 67 ], as well as changes in data sharing quality and flexibility [ 69 ]. Additionally, previous studies have addressed the need for data processing improvements (e.g. [ 77 ]). Some steps for inducing these changes have been suggested in the reviewed studies, such as the successful incorporation of diverse data from various sources of data [ 99 ] and the integration of smart contracts [ 48 ]. These themes specify that past studies in that area have focused on (i) improving technological features, (ii) managing medical databases, also (iii) identifying unique capabilities in the medical field, where blockchain could make remarkable contributions. Based on emerging trends, it can be said that scholarship in this field is still transforming, with existing facets of healthcare being recognized as possible recipients of using blockchain as a result of technological advancements.

Research framework for future synthesis

This analysis and review helped in the framework development which was created with the research gaps identified in existing recommendations suggested in previous research. The research model includes 5components that would aid in the development of the healthcare ecosystem based on blockchain, for future research. The research framework for the BCT-based healthcare system is depicted in Fig 10 .

Data sources

Personal and medical health records are created and managed by the patients using mobile devices, healthcare service suppliers, and pharmaceutics is one of these associated industries., research and insurance [ 32 , 47 , 70 ]. These serve as the foundation of the blockchain architecture and need management by legitimate and regulatory rules. This technology might aid in the development of authorized databases that information can be retrieved by inter-institutional authorities in collaboration with the required agencies to aid in patient treatment and medical decision-making [ 21 , 30 ]. Because of the incorporation of newer technologies, such as smart patient tracking devices [ 53 ], to increase the comprehensiveness of medical databases, future research should concentrate on handling those data sources.

System architecture

With advances in blockchain technology, the system’s architecture will undergo important changes and refinement in terms of the components incorporated into the system of blockchain. Such as using Permissioned consortium blockchain [ 28 ] or platforms other than Ethereum [ 68 , 77 ], could improve current blockchain deployment architectures in the healthcare ecosystem. Also, future research should concentrate on creating techniques for managing system architectures that have been established, particularly the challenging circumstances that can have an impact on the performance and efficiency, for instance, node management [ 74 ] and techniques of key distribution [ 67 ].

Blockchain technology strategic implementation

In the case of increasing integration of information and communication technology and blockchain over healthcare ecosystems, researchers should have focused on the elements which could impede and assist in the widespread application of blockchain technology. According to our findings, we believe that organizations should think about whether or not, by identifying the key issues throughout this study, blockchain technology might prove a potential source of creating or enhancing value. Strategic problems like resource constraints [ 50 ] and technical problems like performance uncertainty [ 56 ] and system requirements are these examples [ 99 ]. Considering these problems might help scholars to develop blockchain architectures that can offer better functional utility and productivity in terms of resource and output management. This can also guide health system administrators and personnel to adopt a holistic and strategic approach to the potential inclusion of blockchain as an essential component of a company’s value chain.

Beneficiaries

Databases built on the blockchain can provide trustworthy information to particular beneficiaries in the sector of healthcare, such as patients who keep ownership of their information. Authorities including doctors, pharmacists, medical researchers, and insurance firms are also beneficiaries. Patients may authorize them to use medical information for a range of purposes, plus collaborative medical decision-making [ 63 ], medical informatics and diagnosis (S.J. [ 61 ]), and fraud prevention [ 47 ]. Because of the blurring of the borders between the health system, wellness sectors, and mobile phones, researchers must recognize such beneficiaries ensuring data is accessed by the relevant authority. Moreover, the important thing is maintaining the integrity of data following ethical and legal bindings. As a result, scholars must concentrate to understand the perspective of the user about the perceived advantages and costs of engaging in a blockchain system. It can assist to identify and remove obstacles in the widespread application and use of blockchain.

Ethical & legal consideration

Blockchain applications are addressing critical issues for example authentication, interoperability, and safe sharing of medical data [ 49 , 118 – 120 ]. Regardless of the increased emphasis on the blockchain, the acceptance of such concerns may be regarded as a remarkable barrier to its extensive adoption. More emphasis should be placed on regulatory compliance [ 100 ] and ethical recommendation for issues like control of ownership and access of patient data [ 99 ]. We propose that future scholars take a multidisciplinary approach to determine avenues for resolving ethical and legal compliance issues in multi-national or cross-institutional contexts for blockchain adoption. We also argue that there is a need to positively impact the public and appease regulatory agencies by deliberating and highlighting the critical benefits derived by using technology based on blockchain.

Directions for future research

According to the SLR, we provide a brief summarization of the thematic problems that would require attention from future researchers:

Deployment of holistic view

In case it is critical to find solutions to security and performance-related problems, like interoperability [ 67 ] and access-control [ 68 ], we argue that scholars must take a broader view of blockchain adoption. This is critical to creating holistic, legally, and ethically compliant [ 21 , 30 ], robust data management, and authentication procedures in e-health ecosystems [ 33 ]. Furthermore [ 36 ], argues that context variables like people and culture may play an important role in the development of new technologies. Eventually, we suggest testing blockchain-based electronic health ecosystems in cross-institutional and cross-national contexts to build tailored context-based healthcare solutions in collaborating with different organizations inside the healthcare space, such as research medical centers [ 60 ].

Optimization of the architecture

Scholars might focus on improving the efficiency and performance of proposed designs to account for the higher transaction rates which may be expected if blockchain is integrated into healthcare operations in the future [ 113 ]. That can be accomplished by dealing with network congestion [ 69 ], scalability [ 99 ], throughput [ 76 ], and bandwidth issues [ 22 ].

Data protection & legal compliance

Addressing data, plus user privacy and legal problems will be an important area of future research [ 21 , 30 , 53 ]. These can be directly tackled by designing blockchain protocols in handling healthcare records that can be enforceable by smart-contract [ 36 ] and compliant with data and privacy protection regulations, for example, Health Insurance Portability and Accountability Act [ 31 , 36 , 53 ].

Other technologies integration

For improved functionality, deployment of block-chain might be advantageous by the technology with business processes in healthcare [ 36 ]. For example, researchers can concentrate to advance the incorporation of edge computing, AI, and ML through blockchain health service ecosystems in developing an improved anticipatory analytic model to provide customized health treatment and diagnostics (e.g. [ 52 , 63 , 64 ]). Furthermore, research may aim to improve accessibility, remote control, and emergency services via the integration of sensors based on IoT. Furthermore, we propose two additional potential directions for future scholars to extend the existing scope of academic boundaries in this sector. First of all, it proposes the requirement to understand the implications of blockchain deployment in more niches in healthcare, but related fields i.e. managing the digital rights of users’ [ 13 ], drug prescription management [ 11 ], and prescription fraud prevention [ 47 ]. Furthermore, the research could be conducted to investigate the implications of blockchain usage across the whole health system supply and value chain. It can help scholars better understand user-related interoperability problems and additionally enables creating standard protocols to use systems working under the blockchain.

This research study is designed to understand completely the application of blockchain in the domain of healthcare. To achieve this goal, SLRs were conducted on nine highly regarded databases using particular protocols to pick out relevant articles for review. The outcomes were used, to sum up, current knowledge on applications of blockchain in the specific sector of medical care, but to also summarize past and the present academic research theme trends in this field. Future research possibilities have been showcased in the form of a synthesized framework created by combining insights from existing restrictions, suggestions, and emerging gaps in current knowledge observed throughout this review.

Supporting information

S1 checklist, funding statement.

The author(s) received no specific funding for this work.

Data Availability

• PLoS One. 2022; 17(4): e0266462.

Decision Letter 0

25 Nov 2021

PONE-D-21-33056Blockchain Technology in Healthcare: A Systematic ReviewPLOS ONE

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Reviewer #2: Yes

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Reviewer #1: irst of all, I congratulate all of the authors for working on the significant topic of blockchain technology in health care. I have a few suggestions listed below:

In table 3, write a complete name instead of writing single alphabets.

Correct the sequence of Figure 6. (i.e. Security and Privacy).

Reviewer #2: In this work, the authors have done a survey on Blockchain Technology in Healthcare. The study is compiled by reviewing research articles published in nine well-reputed venues such as IEEE Xplore, ACM Digital Library, Springs Link, Scopus, Taylor & Francis, Science Direct, PsycINFO, Ovid Medline, and MDPI between January 2016to August 2021. A total of 1,192 research studies were identified out of which 51 articles were selected based on inclusion criteria for this SLR that presents the modern information on the recent implications and gaps in the use of BCT for enhancing the healthcare procedures. A framework is developed to address the probable field where future researchers can add considerable value, such as data protection, system architecture, and regulatory compliance. Hence, The paper can be accepted after making the following Minor corrections.

1. There are few grammatical errors in the manuscript. So English proof reading is required. For example, “The research studies of [13] and [14] have been discussed” could be written as “The research studies of [13] and [14] have discussed”.

2. I don’t find X-Axis and Y-axis values in “Figure 3”.

3. Some important recent references are missing, the following references must be totally added in the Section "References" (otherwise, the reference is not enough, then it must be revised again until it is enough):

The Application of the Blockchain Technology in Voting Systems: A Review

Homechain: A blockchain-based secure mutual authentication system for smart homes

Human-in-the-loop-aided privacy-preserving scheme for smart healthcare

Profile Matching for IoMT: A Verifiable Private Set Intersection Scheme

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Author response to Decision Letter 0

12 Feb 2022

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Decision Letter 1

22 Mar 2022

Blockchain Technology in Healthcare: A Systematic Review

PONE-D-21-33056R1

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• Frontiers in Built Environment
• Building Information Modelling (BIM)
• Research Topics

Blockchain-enabled Sustainable and Smart Construction

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About this Research Topic

The construction industry, known as a significant contributor to greenhouse gas emissions and energy consumption, must urgently prioritize sustainability and efficiency in response to the pressing challenges posed by climate change and the energy crisis. Sustainable construction projects encounter obstacles such as data loss, fraudulent activities, and inefficient information exchange. Additionally, the lack of digitalization, weak collaboration, and inadequate privacy measures in the construction process result in escalating costs, dissatisfaction, and compromised service quality, thereby impeding progress in sustainable development within the field. To address these critical issues, blockchain technology emerges as a promising solution. By leveraging a distributed ledger system based on cryptography, blockchain ensures immutability, reliability, traceability, and authentication without the need for third-party intermediaries. Furthermore, the implementation of smart contracts facilitates automatic task execution, streamlining processes and enhancing efficiency. Integration with other advanced technologies, often referred to as "blockchain+", further enhances its potential, particularly in terms of intelligence and automation. Considering these advantages, blockchain emerges as an essential tool for the construction industry to foster sustainability, automation, and intelligence. By harnessing the power of this transformative technology, the construction sector can play a pivotal role in combatting climate change and alleviating the energy crisis. The discussions around blockchain in the construction industry are still in their early stages, necessitating further exploration in several key areas: (1) Identifying Potential Applications: There is a need to discover more potential applications of blockchain in construction. Real-world tests and projects are crucial to validate the feasibility and effectiveness of implementing blockchain solutions in various construction scenarios. (2) Sustainable Blockchain Design: Designing or selecting a sustainable and appropriate type of blockchain for specific construction use cases is essential. Understanding how to match the characteristics of blockchain with the unique requirements of construction processes will be pivotal in maximizing its benefits. (3) Integration with State-of-the-Art Technologies: Exploring the integration of blockchain with other cutting-edge technologies, such as the Internet of Things (IoT), Artificial Intelligence (AI), and Machine Learning (ML), will pave the way for a sustainable and intelligent future in construction. Understanding how these technologies can complement and enhance each other is critical for fostering innovation. (4) Contribution to Carbon Neutrality: Considering the urgent need to achieve carbon neutrality, exploring how blockchain can contribute to carbon monitoring, tracking, and accounting is vital. Blockchain's inherent capabilities of transparency and immutability can facilitate effective carbon management strategies. This Research Topic aims to ignite scholarly discussions on the practical application of blockchain in construction. By promoting the adoption of blockchain in real-world construction projects, the industry can make significant strides in enhancing sustainability and efficiency. Embracing blockchain technology holds the potential to revolutionize the construction sector and propel it towards a more sustainable and eco-friendly future. This Research Topic centers around the profound impact of blockchain technology on the construction industry, aiming to capitalize on new opportunities and develop sustainable and intelligent solutions. The scope includes diverse topics of interest, with an emphasis on the application of blockchain in construction. Potential areas of exploration are as follows: • Comprehensive Review and Development Path: Papers focusing on reviewing the trends, development path, and diffusion patterns of blockchain in the construction sector, providing valuable insights into its growth and potential. • Blockchain in the Green Supply Chain: Investigations into how blockchain can revolutionize the green supply chain in construction, particularly in areas like prefabricated and modular construction, to enhance sustainability and environmental stewardship. • Carbon Monitoring and Accounting: Explorations of how blockchain can play a pivotal role in carbon monitoring, tracking, and accounting throughout the construction process, helping the industry achieve its carbon reduction and environmental goals. • Life Cycle (Sustainability) Assessment: Research on the application of blockchain technology in life cycle assessments, enabling a more holistic understanding of a construction project's environmental impact and sustainability performance. • Sustainable-Oriented Decision-Making: Studies highlighting the integration of blockchain in decision-making processes for sustainability-focused aspects in construction, such as material selection, energy-saving initiatives, and innovative structural designs. • Impact on the Construction Industry: Evaluations of the overall impact of blockchain technology on the construction industry, including its potential to drive positive changes, optimize processes, and create new opportunities. • Adoption Challenges and Opportunities: In-depth analyses of the challenges and opportunities faced during the adoption of blockchain in construction, shedding light on strategies for successful implementation. • Integration with Advanced Technologies: Exploration of how blockchain can be effectively integrated with other state-of-the-art technologies, such as the Internet of Things (IoT), Building Information Modeling (BIM), and Artificial Intelligence (AI), and their potential collaborative applications in construction. • Sustainable Blockchain Type Selection: Research focusing on the design and selection of sustainable and appropriate blockchain types tailored to specific construction scenarios, ensuring optimized functionality and efficiency. • Roadmaps for Future Policies: Papers providing insights and recommendations for future policies and regulations related to the application and integration of blockchain technology in the construction industry. By delving into these compelling topics, this Research Topic seeks to foster a deep understanding of blockchain's transformative potential in construction and its pivotal role in shaping a sustainable and intelligent future for the industry.

Keywords : Blockchain, Sustainability, Smart, Construction

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A Blockchain Research Framework

What We (don’t) Know, Where We Go from Here, and How We Will Get There

• State of the Art
• Published: 05 December 2017
• Volume 59 , pages 385–409, ( 2017 )

Cite this article

• Marten Risius 1 &
• Kai Spohrer 2  

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While blockchain technology is commonly considered potentially disruptive in various regards, there is a lack of understanding where and how blockchain technology is effectively applicable and where it has mentionable practical effects. This issue has given rise to critical voices that judge the technology as over-hyped. Against this backdrop, this study adapts an established research framework to structure the insights of the current body of research on blockchain technology, outline the present research scope as well as disregarded topics, and sketch out multidisciplinary research approaches. The framework differentiates three groups of activities (design and features, measurement and value, management and organization) at four levels of analysis (users and society, intermediaries, platforms, firms and industry). The review shows that research has predominantly focused on technological questions of design and features, while neglecting application, value creation, and governance. In order to foster substantial blockchain research that addresses meaningful questions, this study identifies several avenues for future studies. Given the breadth of open questions, it shows where research can benefit from multidisciplinary collaborations and presents data sources as starting points for empirical investigations.

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Blockchain in a Business Model: Exploring Benefits and Risks

Exploring the role of blockchain technology in value creation: a multiple case study approach

The Value and Applications of Blockchain Technology in Business: A Systematic Review of Real Use Cases

We provide open access to the overview of current scientific knowledge [Table  2 and Table A1 (in the appendix, available online via http://link.springer.com )] here: http://bit.ly/BCSOTA . We are thankful to Florian Glaser for his inspiring feedback to the avenues for future research.

In the following also interchangeably referred to as “blockchain”, “blockchain systems”, “blockchain environment”, or “decentralized blockchain”.

We provide open access to the overview of current scientific knowledge (Table  2 ) here: http://bit.ly/BCSOTA .

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College of Business and Behavioral Science, Clemson University, 515 Calhoun Dr, Clemson, SC, 29634, USA

Marten Risius

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Risius, M., Spohrer, K. A Blockchain Research Framework. Bus Inf Syst Eng 59 , 385–409 (2017). https://doi.org/10.1007/s12599-017-0506-0

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Received : 11 January 2017

Accepted : 14 August 2017

Published : 05 December 2017

Issue Date : December 2017

DOI : https://doi.org/10.1007/s12599-017-0506-0

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Blockchain could offer a solution to the UK's transport ticketing systems

A new approach to transport ticketing offers a step towards an integrated, transparent system that works efficiently for both ticket providers and passengers across all modes of transport.

Traditional ticketing systems are based on solutions that are vulnerable to issues including a lack of transferability across multi-modal transport networks, and an inability to adapt to policy changes and new technologies.

Experts at the University of Birmingham have outlined a system that offers a new foundation for all ticketing providers. In a new paper, published in IET Blockchain , STUB (System for Ticketing Ubiquity within Blockchains) brings together the capabilities of two versatile technologies -- blockchain and ontology.

A blockchain is a distributed ledger that that records transactions in a way that ensures security, transparency, and immutability. An ontology is formal representation of knowledge within a domain and the relationships between those concepts, used to model and manage complex information systems.

The researchers showed how both technologies could be combined to create a robust, transparent, and interconnected data framework that ensures consistent and reliable shared knowledge.

Utilising these data structures, ticket providers can sell and validate tokenised tickets on the blockchain, ensuring universal accessibility across all providers. The integration of ontology allows providers to capture and share contextual information about the transport network, enabling providers to offer comprehensive data about routes, schedules, and availability, thereby streamlining the ticketing process.

Lead author, Dr Joe Preece, said: "Transport systems around the world are becoming increasingly interconnected. Ticketing systems are key to this and there is a growing interest in the use of smarter transport ticketing that harnesses emerging technologies to overcome the limitations of traditional systems.

"The system we have devised enables ticket providers to operate in a more transparent, flexible environment, that will ultimately offer passengers a more user-friendly experience.

"STUB's approach is not to be a single central data platform with transport policy baked-in, but instead to be a policy-agnostic approach that empowers existing ticket providers and technologies to share core ticketing data and to build new solutions on top of.

"In essence, this may provide a modernised approach to the Rail Settlement Plan, that enables multi-modal ticketing, automated revenue and refund allocation, and dynamic fare pricing, whilst retaining the technologies in the sector that already work well.

The next step for the team will be to set up a pilot scheme for the technology in a regional transport network, to demonstrate its efficacy, and to get feedback from ticket operators and passengers.

"A big challenge to implementation will be the integration with existing ticketing infrastructure to work alongside the current standardised approaches whilst we scale up the technology. Setting up a successful pilot will be key to breaking down these barriers."

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Materials provided by University of Birmingham . Note: Content may be edited for style and length.

Journal Reference :

• Joseph D. Preece, Christopher R. Morris, John M. Easton. Leveraging ontochains for distributed public transit ticketing: An investigation with the system for ticketing ubiquity with blockchains . IET Blockchain , 2024; DOI: 10.1049/blc2.12071

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