2. Methods
This study employed the systematic literature review (SLR) method. An SLR offers a structured approach for reviewing and ensuring the quality of primary studies on specific topics to address defined research questions. Initially utilized in medical research during the early nineties, the SLR method facilitated evidence-based research practices, aiding researchers in making informed decisions regarding treatment options within the medical field. Over time, SLR methods have been adopted across various research domains, including business, engineering, and social sciences. They have become increasingly prevalent in diverse research fields, serving to assess the current state of research within specified study areas and providing insights to guide future exploration for fellow researchers.
The tertiary study encompasses review articles, mapping studies, and scoping studies focusing on technical challenges related to the blockchain. Mapping studies seek to identify research within specified primary studies and pinpoint research gaps. Similarly, scoping studies aim to classify research within primary studies and identify research gaps. However, these three literature review methods share similarities and can be distinguished primarily by their approaches to analyzing and presenting the literature.
This study presents a review of primary studies, making this study a secondary study, also known as an overview of primary studies. This study follows the SLR guidelines of Kitchenham and Charters [
5]. As per this guideline, there are four main steps in SLR. The first step is to define a research question and then search for relevant articles from the scientific database, followed by a screening of extracted articles based on predetermined criteria and a review of the selected article.
3. Findings
This section describes the findings in detail. The results are presented according to the research questions mentioned in
Section 2.
RQ1. How many SLRs have been published since blockchain technology emerged as Bitcoin (2009) to date (2023), and what is their quality?
This study identified 29 articles that met the criteria for objective and selection criteria. Following a thorough quality assessment, 21 articles were selected for a detailed review, comprising 17 peer-reviewed journal articles, three conference papers, and one book chapter (
Table 6). The quality scores for these articles ranged between 6.5 and 9.5, as shown in
Table 5.
Table 7 lists the articles selected for further review and analysis.
The first systematic literature review addressing technical challenges in blockchain was published in 2016 [
1]. Despite the absence of relevant reviews in 2017, the volume of review articles saw a significant increase by 2020 (
Figure 3). Only four conference papers met both the selection and quality criteria. No umbrella review that encompassed all blockchain challenges was identified. Among the articles, only two peer-reviewed and one conference paper covered more than one technical challenge. It was noted that smart contracts, a critical component of blockchain technology, received extensive coverage (
Table 6). Other aspects, such as consensus mechanisms, privacy, and interoperability, were less frequently reviewed, though there was an abundance of survey literature addressing these challenges.
Smart contracts emerged as the most extensively reviewed blockchain element, particularly focusing on their security and coding language interoperability. This intense scrutiny is primarily due to their widespread use in the business sector and their role in enabling distributed applications (dApps) [
1].
RQ2. What research areas are addressed in the SLRs on blockchain technical challenges?
A multitude of technical challenges in blockchain technology has been systematically examined in the literature, including security, scalability, smart contract integrity, privacy, data storage, governance, and interoperability [
1,
8,
9,
10,
11,
12]. Security concerns, particularly the threat of a 51% attack and the vulnerabilities associated with private and public key infrastructures, represent the most extensively reviewed topics within blockchain research [
1,
8]. Moreover, the security of smart contracts has been a focal point, with studies highlighting that the integrity of decentralized applications (dApps) hinges critically on the robustness of smart contract frameworks; any compromise can potentially destabilize the entire system [
13,
14].
Scalability challenges have also been a major point of discussion, particularly in industrial applications of blockchain, where the demands on system capacity often exceed what decentralized architectures can typically support, especially when contrasted with centralized systems [
12]. Within second-generation blockchain platforms, issues around smart contract security and privacy have been rigorously debated [
14,
15,
16,
17,
18].
Blockchain interoperability, described as a pivotal hurdle, affects the seamless integration of blockchain systems across varied business domains, aiming to create a decentralized internet-like network [
10]. Additional challenges reviewed include data privacy and governance issues related to consensus mechanisms, performance bottlenecks, data storage constraints, and the synchronization time required for block confirmation [
1,
19].
Moreover, the literature has extensively covered the technical difficulties associated with smart contract implementation and execution [
11,
13,
14,
15,
16,
17,
18]. These discussions have dissected various components of smart contract functionality, such as security vulnerabilities [
14], code flaws [
18], susceptibility to hacking, and the limitations inherent in executing contracts drafted in natural language. The translation of natural language into executable smart contract code remains a particularly daunting challenge, given the nuanced and context-dependent nature of legal language in various sectors [
17,
18]. This area, vital for ensuring that smart contracts serve as valid and legally binding agreements, continues to require significant advancements to bridge the gap between legal stipulations and technical execution.
RQ3. What are the major technical factors that challenge the integration of blockchain technology in various industries?
One of the principal technical challenges limiting industry-specific blockchain applications is interoperability—the capability of different systems to exchange and use information effectively [
8,
10]. The isolated nature of blockchain development often results in “islanding”, which disrupts the seamless transmission of data between different blockchains, undermining core features such as immutability and transparency [
10]. Another significant challenge is scalability, which, in comparison to traditional centralized systems used in industries, tends to be lower due to the intensive consensus mechanisms like Proof of Work and the decentralized architecture of blockchain systems [
8,
9,
12,
20]. Various new methodologies have been proposed in the literature to enhance scalability through both on-chain and off-chain models, including approaches like pipelining, content delivery networks, payment channels, sharding, parallel mining, system redesign, and hardware-assisted strategies [
12]. However, these scalability solutions introduce their own set of challenges, such as the rational behavior of nodes and the need for trusted hardware in various sharding methods, which may not always be feasible [
12]. Additionally, issues like blockchain size and data redundancy have been identified as factors discouraging the wider adoption of blockchain technology across different industries [
12].
RQ4. What technical challenges need more attention to implement mainstream blockchain technology in various business verticals?
One of the least examined technical challenges in blockchain research concerns interoperability and integration with existing legacy systems. Various interoperability schemes have been discussed in the studies, such as [
7,
15]. Blockchain systems often operate as isolated distributed ledgers, making it difficult to integrate and manage data across different blockchain systems. Industries might benefit from adopting blockchain solutions with interoperability features that facilitate interactions with sub-vendors and partners within their supply chains [
10]. Additionally, integrating legacy systems with blockchain technology has received inadequate attention. Developing an efficient and effective bridge that facilitates data transactions between legacy and blockchain systems is crucial for future blockchain advancements. It is essential to establish an interoperability protocol that allows for a seamless, cost-effective transition from legacy database systems to blockchain, benefiting various industries.
Another underexplored area is the impact of the blockchain on data protection regulations, such as the General Data Protection Regulation (GDPR) implemented by several European Union countries. As consumer data privacy becomes increasingly critical and more countries consider similar regulations allowing users to request data deletion, the immutable nature of blockchain presents challenges in this aspect [
21]. The blockchain does not naturally allow for data modification or deletion. However, the literature proposes several methods to address these issues, such as pseudonymization, which allows for the removal of partial user data [
22]. Additionally, off-chain approaches store sensitive data outside the blockchain, using cryptographic techniques that preserve identity privacy, such as zero-knowledge proofs, attribute-based signatures, and ring signatures [
19]. Despite these methods, no one currently offers a complete solution for the “Right to Forget” or the complete deletion of data on a blockchain.
RQ5. What progress has been achieved in the course from one study to another in the research timeline, and how does it address the challenges that business faces in technology integration?
The blockchain is an emerging field of research that has been expanding rapidly as efforts intensify to address its limitations and enhance its performance to meet industry needs. In previous studies, such as [
1], only a few technical challenges have been addressed, including issues related to throughput, latency, size, bandwidth, security, resource wastage, usability, and forks. Many of these challenges, such as resource wastage, forks, and usability issues, are specifically linked to first-generation blockchains like Bitcoin. However, second-generation blockchains like Hyperledger have addressed usability problems by incorporating REST APIs into the blockchain framework. Additionally, the shift from a proof of work consensus mechanism to more efficient ones like proof of stake or Raft consensus [
8] has mitigated issues related to resource wastage. Subsequent reviews have broadened the scope of challenges addressed, recognizing the need for interoperability among different blockchain systems and data transferability between blockchain and traditional systems [
10] to support globally integrated business models.
While significant progress has been noted in addressing scalability, user interaction, security, and privacy within blockchain technology, other critical aspects such as interoperability, data immutability in compliance with the “Right to Forget” laws, and the integration of oracles (which allow external data to be used as inputs in blockchain smart contracts) have been less thoroughly explored. Although various mechanisms to achieve interoperability have been proposed, there is no widely accepted standard method yet. Furthermore, the issue of user data privacy is increasingly concerning due to rising cybersecurity attacks and data thefts, prompting governments to enact legislation like the GDPR to enhance user control over their data [
22]. However, only a limited number of studies have reviewed this aspect [
21,
22].
Table 7.
Articles included for review.
ID | Title | Year | Ref |
---|
R1 | Where is current research on Blockchain technology?—A systematic review | 2016 | [1] |
R2 | Smart contract applications within blockchain technology: A systematic mapping study | 2018 | [15] |
R4 | Blockchain smart contracts formalisation: Approaches and challenges to address vulnerabilities | 2019 | [16] |
R5 | Blockchains: A Systematic Multivocal Literature Review | 2020 | [8] |
R7 | Blockchain from the Perspective of Privacy and Anonymisation: A Systematic Literature Review | 2020 | [19] |
R8 | Model-Based Software Design and Testing in Blockchain Smart Contracts: A Systematic Literature Review | 2020 | [11] |
R9 | A systematic literature review of blockchain and smart contract development: Techniques, tools, and open challenges | 2020 | [17] |
R10 | An empirical review on blockchain smart contracts: Application and challenges in implementation | 2020 | [13] |
R13 | Consensus Mechanisms in Distributed Ledgers for the Protection of Confidential Data: A Multivocal Literature Review | 2020 | [23] |
R14 | A comprehensive survey on smart contract construction and execution: paradigms, tools, and systems | 2021 | [18] |
R15 | GDPR Compliant Blockchains—A Systematic Literature Review | 2021 | [21] |
R16 | Security, Performance, and Applications of Smart Contracts: A Systematic Survey | 2019 | [14] |
R17 | Systematic Literature Review of Challenges in Blockchain Scalability | 2020 | [9] |
R18 | A systematic review of blockchain scalability: Issues, solutions, analysis and future research | 2021 | [20] |
R20 | A Systematic Literature Review of Blockchain Consensus Protocols | 2021 | [24] |
R21 | A Systematic Literature Review Toward a Blockchain Benchmarking Framework | 2022 | [25] |
R22 | Blockchain Architectural Concerns: A Systematic Mapping Study | 2022 | [26] |
R23 | Interoperability Among Heterogeneous Blockchains: A Systematic Literature Review | 2021 | [10] |
R25 | Scalable blockchains—A systematic review | 2022 | [12] |
R28 | A systematic literature review on blockchain governance | 2023 | [27] |
R29 | A systematic literature review of the tension between the GDPR and public blockchain systems | 2023 | [22] |