Research

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16 pages, 1268 KiB

Open AccessArticle

Performance of PBFT Consensus under Voting by Groups

by Vojislav B. Mišić, Jelena Mišić and Xiaolin Chang

Blockchains 2024, 2(2), 134-149; https://doi.org/10.3390/blockchains2020007 (registering DOI) - 26 Apr 2024

Practical Byzantine Fault Tolerance (PBFT) is the protocol of choice for many applications that require distributed consensus between a number of participant nodes. While PBFT assumes a single voting committee, many applications recognize different groups of participants that need to reach a consensus [...] Read more.

Practical Byzantine Fault Tolerance (PBFT) is the protocol of choice for many applications that require distributed consensus between a number of participant nodes. While PBFT assumes a single voting committee, many applications recognize different groups of participants that need to reach a consensus separately before accepting a proposal. To this end, we propose to count the votes by separate groups or committees of participating nodes, instead of all together as in the original PBFT. We then investigate the performance impact of this approach on the mean time to accept a data block and the number of nodes involved in making the final decision. Our results indicate that the proposed solutions impose a slight performance penalty which may be countermanded by reducing the quorum numbers needed in different subsets of the original committee. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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28 pages, 1647 KiB

Open AccessArticle

Decision Model to Design Trust-Focused and Blockchain-Based Health Data Management Applications

by Christina Erler, Ann-Marit Bauer, Friedrich Gauger and Wilhelm Stork

Blockchains 2024, 2(2), 79-106; https://doi.org/10.3390/blockchains2020005 - 09 Apr 2024

Viewed by 317

Abstract

Many Blockchain-based approaches have been published in the field of health data management applications (HDMAs). However, no comprehensive guideline exists to guide the multiple and interdependent design decisions to develop such systems. This paper aims to support the HDMA system design processes by [...] Read more.

Many Blockchain-based approaches have been published in the field of health data management applications (HDMAs). However, no comprehensive guideline exists to guide the multiple and interdependent design decisions to develop such systems. This paper aims to support the HDMA system design processes by introducing a novel decision model. The model considers all relevant requirements, from regulatory context to user needs and trust considerations. To generate the decision model, we define a taxonomy that organizes previously published approaches by their technical design features and combines it with the trust assumptions of the participating actors according to the STRIDE method. The model aims to support a cohesive overall system design by addressing Blockchain type, off-chain storage, identity and access management, security decisions, and the specific use case of data donation. A group of experts evaluated the decision tree and its utility is demonstrated in three representative use cases. Special attention is paid to the use case of data donation via a data trustee, which is examined in detail. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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21 pages, 846 KiB

Open AccessArticle

Decision Tree-Based Federated Learning: A Survey

by Zijun Wang and Keke Gai

Blockchains 2024, 2(1), 40-60; https://doi.org/10.3390/blockchains2010003 - 07 Mar 2024

Viewed by 838

Abstract

Federated learning (FL) has garnered significant attention as a novel machine learning technique that enables collaborative training among multiple parties without exposing raw local data. In comparison to traditional neural networks or linear models, decision tree models offer higher simplicity and interpretability. The [...] Read more.

Federated learning (FL) has garnered significant attention as a novel machine learning technique that enables collaborative training among multiple parties without exposing raw local data. In comparison to traditional neural networks or linear models, decision tree models offer higher simplicity and interpretability. The integration of FL technology with decision tree models holds immense potential for performance enhancement and privacy improvement. One current challenge is to identify methods for training and prediction of decision tree models in the FL environment. This survey addresses this issue and examines recent efforts to integrate federated learning and decision tree technologies. We review research outcomes achieved in federated decision trees and emphasize that data security and communication efficiency are crucial focal points for FL. The survey discusses key findings related to data privacy and security issues, as well as communication efficiency problems in federated decision tree models. The primary research outcomes of this paper aim to provide theoretical support for the engineering of federated learning with decision trees as the underlying training model. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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20 pages, 2339 KiB

Open AccessArticle

Zk-SNARKs-Based Anonymous Payment Channel in Blockchain

by Yunwei Guo, Haochen Liang, Liehuang Zhu and Keke Gai

Blockchains 2024, 2(1), 20-39; https://doi.org/10.3390/blockchains2010002 - 05 Feb 2024

Viewed by 615

Abstract

Payment channels serve as an effective solution to the scalability problem of cryptocurrencies, which significantly increase transaction rates by allowing users to conduct large-scale offline transactions off-chain without posting everything to the blockchain. However, the existing payment channels lack privacy protection for the [...] Read more.

Payment channels serve as an effective solution to the scalability problem of cryptocurrencies, which significantly increase transaction rates by allowing users to conduct large-scale offline transactions off-chain without posting everything to the blockchain. However, the existing payment channels lack privacy protection for the transaction amount and the linking relationship between the two parties to the transaction. Therefore, in order to address the scalability and privacy issues of cryptocurrencies such as Bitcoin, this paper proposes a zk-SNARKs-based anonymous payment channel (zk-APC), which supports an unlimited number of off-chain payments between the payer and the payee and protects the privacy of the participants. Specifically, the proposed scheme achieves relational anonymity and amount privacy for both on-chain and off-chain transactions in the payment channel through utilizing zero-knowledge proof (zk-SNARKs) and commitment schemes. This paper proves that the proposed method is more effective than similar schemes through a performance evaluation. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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19 pages, 567 KiB

Open AccessArticle

Decentralization Is Good or Not? Defending Consensus in Ethereum 2.0

by Vojislav B. Mišić, Soosan Naderi Mighan, Jelena Mišić and Xiaolin Chang

Blockchains 2024, 2(1), 1-19; https://doi.org/10.3390/blockchains2010001 - 23 Jan 2024

Viewed by 685

Abstract

Proof-of-Stake (PoS) protocols are widely accepted as a viable substitute for the Proof-of-Work-based consensus, which is why recent blockchain-based cryptocurrencies and applications, most notably Ethereum 2.0, are using some variant of PoS as the basis for the consensus protocol. However, the implementation of [...] Read more.

Proof-of-Stake (PoS) protocols are widely accepted as a viable substitute for the Proof-of-Work-based consensus, which is why recent blockchain-based cryptocurrencies and applications, most notably Ethereum 2.0, are using some variant of PoS as the basis for the consensus protocol. However, the implementation of PoS protocols in Ethereum 2.0 are not without its share of problems and vulnerabilities, especially with respect to the malicious behavior of validator nodes. In this paper, we first review the basic tenets of PoS protocols. We then discuss some of the recently described attacks on the Ethereum 2.0 consensus, and we also show that some of the design rationales adopted in PoS implementation—the decentralization of the voting process in particular—have, in actuality, enabled attacks that can be launched at a very low cost to the attacker. We also propose simple remedies that can reduce or eliminate the impact of those attacks and can evaluate the performance of the Ethereum 2.0 consensus when these remedies are applied. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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Review

Jump to: Research

21 pages, 688 KiB

Open AccessReview

Web3: Exploring Decentralized Technologies and Applications for the Future of Empowerment and Ownership

by Yiwei Lai, Jingyi Yang, Mingzhe Liu, Yibei Li and Shanlin Li

Blockchains 2023, 1(2), 111-131; https://doi.org/10.3390/blockchains1020008 - 11 Dec 2023

Viewed by 2768

Abstract

The emergence of the World Wide Web has revolutionized online communication, aiming to achieve global information sharing and communication. However, the current Web 2.0 architecture, which relies on centralized platforms, presents limitations such as restricted user rights, data privacy concerns, and dependence on [...] Read more.

The emergence of the World Wide Web has revolutionized online communication, aiming to achieve global information sharing and communication. However, the current Web 2.0 architecture, which relies on centralized platforms, presents limitations such as restricted user rights, data privacy concerns, and dependence on centralized institutions. Web3, as a concept describing the next evolutionary stage of the internet, offers a solution to these issues by reshaping the internet infrastructure. Web3 provides a foundation for autonomous digital experiences and drives the advancement of the digital economy. This paper offers a thorough exploration of Web3, covering its key technologies, applications, challenges, and opportunities. We begin by introducing the core technologies behind Web3, followed by an exploration of its prominent applications. Finally, we analyze the challenges faced by Web3 and discuss potential research opportunities to address these challenges in the future. In summary, this study comprehensively elaborates on Web3 and lays a solid foundation for subsequent research work, encouraging researchers to explore new frontiers. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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21 pages, 4706 KiB

Open AccessReview

Bitcoin and Renewable Energy Mining: A Survey

by Yusuke Tomatsu and Wenlin Han

Blockchains 2023, 1(2), 90-110; https://doi.org/10.3390/blockchains1020007 - 07 Dec 2023

Cited by 1 | Viewed by 901

Abstract

Bitcoin, the most valuable and energy-consuming cryptocurrency, has recently been at the center of a heated debate over its environmental impact. This controversy has caught the public’s attention, prompting us to investigate the energy consumption of Bitcoin. In this paper, we have conducted [...] Read more.

Bitcoin, the most valuable and energy-consuming cryptocurrency, has recently been at the center of a heated debate over its environmental impact. This controversy has caught the public’s attention, prompting us to investigate the energy consumption of Bitcoin. In this paper, we have conducted a review of the literature on various aspects of Bitcoin mining, including its mechanisms, energy consumption, mining sites, and the potential for renewable energy use. Our findings reveal that the power consumption of Bitcoin is bound to increase with the continued adoption of the proof-of-work (PoW) consensus algorithm. Nonetheless, the growing availability of affordable renewable energy sources worldwide brings hope that Bitcoin mining will shift towards cleaner energy in the near future. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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17 pages, 2423 KiB

Open AccessReview

Blockchain and Healthcare: A Critical Analysis of Progress and Challenges in the Last Five Years

by Hamed Taherdoost

Blockchains 2023, 1(2), 73-89; https://doi.org/10.3390/blockchains1020006 - 08 Nov 2023

Cited by 4 | Viewed by 2537

Abstract

Utilizing the fundamental characteristics of the decentralization, immutability, and transparency of blockchain technology, the healthcare industry has made notable advancements in incorporating it over the past five years. This review examines the progress and challenges encountered in this critical study by assessing 124 [...] Read more.

Utilizing the fundamental characteristics of the decentralization, immutability, and transparency of blockchain technology, the healthcare industry has made notable advancements in incorporating it over the past five years. This review examines the progress and challenges encountered in this critical study by assessing 124 articles published by MDPI between 2018 and the current date. Examining blockchain’s potential uses, like safe data exchange and interoperability in supply chain management and electronic health records, provides exciting new directions for the future of healthcare. Blockchain technology can greatly increase efficiency and cost-effectiveness by guaranteeing data integrity, protecting patient privacy, and reducing administrative procedures. This paper objectively evaluates blockchain’s advancement in healthcare through a thorough analysis of real-world applications and research projects. By highlighting both its advantages and disadvantages, this analysis seeks to add to the continuing conversation about how blockchain will influence the way healthcare is managed and delivered in the future. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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15 pages, 2054 KiB

Open AccessReview

Blockchain Technology Application in Security: A Systematic Review

by Nazanin Moosavi and Hamed Taherdoost

Blockchains 2023, 1(2), 58-72; https://doi.org/10.3390/blockchains1020005 - 29 Oct 2023

Viewed by 3562

Abstract

Blockchain technology is a promising technology that attracts popularity among researchers. However, it was first introduced with digital currencies, particularly Bitcoin, but nowadays, it is also known as one of the most frequently used techniques for securing networks. This systematic review research identifies [...] Read more.

Blockchain technology is a promising technology that attracts popularity among researchers. However, it was first introduced with digital currencies, particularly Bitcoin, but nowadays, it is also known as one of the most frequently used techniques for securing networks. This systematic review research identifies studies that use blockchain for their security challenges. In addition, different fields in blockchain usage, blockchain categorization type, consensus mechanism, smart contract usage, and integration with other software-based algorithms are also investigated. Our results maintain that the Internet of Things (IoT) is the main field in which blockchain provides security. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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15 pages, 1153 KiB

Open AccessReview

Recommendation Systems for the Metaverse

by Lingwen Wei, Xutian Wang, Ting Wang, Zhilan Duan, Yan Hong, Xiaoming He and Huawei Huang

Blockchains 2023, 1(1), 19-33; https://doi.org/10.3390/blockchains1010003 - 24 Aug 2023

Cited by 3 | Viewed by 1572

Abstract

The metaverse, a virtual world closely intertwined with reality, represents the next-generation form of the Internet and encompasses advanced sociability and interaction. With the rapid growth of users and virtual products within this environment, the importance of recommendation systems becomes paramount. This article [...] Read more.

The metaverse, a virtual world closely intertwined with reality, represents the next-generation form of the Internet and encompasses advanced sociability and interaction. With the rapid growth of users and virtual products within this environment, the importance of recommendation systems becomes paramount. This article presents a comprehensive survey that examines the technologies influencing the development of recommendation systems tailored for the metaverse. Firstly, we identify the key trends and fundamental concepts associated with these systems. Secondly, we delve into the core supporting technologies and application scenarios within metaverse recommendation systems. Lastly, we provide insights into future research directions for this rapidly evolving field. Our survey reveals that while progress has been achieved, further investigation is necessary to optimize the technical layout and content of metaverse recommendation systems. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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16 pages, 1740 KiB

Open AccessReview

A Review of Approaches for Detecting Vulnerabilities in Smart Contracts within Web 3.0 Applications

by Hui Li, Ranran Dang, Yao Yao and Han Wang

Blockchains 2023, 1(1), 3-18; https://doi.org/10.3390/blockchains1010002 - 23 Aug 2023

Cited by 1 | Viewed by 2411

Abstract

Smart contracts, programs running on a blockchain, play a crucial role in driving Web 3.0 across a variety of domains, such as digital finance and future networks. However, they currently face significant security vulnerabilities that could result in potential risks and losses. This [...] Read more.

Smart contracts, programs running on a blockchain, play a crucial role in driving Web 3.0 across a variety of domains, such as digital finance and future networks. However, they currently face significant security vulnerabilities that could result in potential risks and losses. This paper outlines the inherent vulnerabilities of smart contracts, both those typical of their applications and those unique to Web 3.0 applications. We then systematically classify the techniques based on their core approach to detecting vulnerabilities in smart contracts. Using these approaches, we conduct a comparative analysis of existing tools in terms of their vulnerability coverage, detection effectiveness, open-source availability, and integration capabilities. Finally, we present the Co-Governed Sovereignty Multi-Identifier Network (CoG-MIN) as a case study to demonstrate the significance of smart contract application security in establishing a community with a shared future in cyberspace during the Web 3.0 era and anticipate future research directions with challenges. To conclude, this study addresses the gap in integrating existing smart contract security research with the advancement of Web 3.0 development, while also providing recommendations for future research directions. Full article

(This article belongs to the Special Issue Feature Papers in Blockchains)

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