TL;DR: This taxonomy captures major architectural characteristics of blockchains and the impact of their principal design decisions and is intended to help with important architectural considerations about the performance and quality attributes of blockchain-based systems.
Abstract: Blockchain is an emerging technology for decentralised and transactional data sharing across a large network of untrusted participants. It enables new forms of distributed software architectures, where agreement on shared states can be established without trusting a central integration point. A major difficulty for architects designing applications based on blockchain is that thetechnology has many configurations and variants. Since blockchains are at an early stage, there is little product data or reliable technology evaluation available to compare different blockchains. In this paper, we propose how to classify and compare blockchains and blockchain-based systems to assist with the design and assessment of their impact on software architectures. Our taxonomy captures major architectural characteristics of blockchains and the impact of their principal design decisions. This taxonomy is intended to help with important architectural considerations about the performance and quality attributes of blockchain-based systems.
TL;DR: This paper provides a systematic vision of the organization of the blockchain networks, a comprehensive survey of the emerging applications of blockchain networks in a broad area of telecommunication, and discusses several open issues in the protocol design for blockchain consensus.
Abstract: The past decade has witnessed the rapid evolution in blockchain technologies, which has attracted tremendous interests from both the research communities and industries. The blockchain network was originated from the Internet financial sector as a decentralized, immutable ledger system for transactional data ordering. Nowadays, it is envisioned as a powerful backbone/framework for decentralized data processing and data-driven self-organization in flat, open-access networks. In particular, the plausible characteristics of decentralization, immutability, and self-organization are primarily owing to the unique decentralized consensus mechanisms introduced by blockchain networks. This survey is motivated by the lack of a comprehensive literature review on the development of decentralized consensus mechanisms in blockchain networks. In this paper, we provide a systematic vision of the organization of blockchain networks. By emphasizing the unique characteristics of decentralized consensus in blockchain networks, our in-depth review of the state-of-the-art consensus protocols is focused on both the perspective of distributed consensus system design and the perspective of incentive mechanism design. From a game-theoretic point of view, we also provide a thorough review of the strategy adopted for self-organization by the individual nodes in the blockchain backbone networks. Consequently, we provide a comprehensive survey of the emerging applications of blockchain networks in a broad area of telecommunication. We highlight our special interest in how the consensus mechanisms impact these applications. Finally, we discuss several open issues in the protocol design for blockchain consensus and the related potential research directions.
TL;DR: An in-depth survey of BCoT is presented and the insights of this new paradigm are discussed and the open research directions in this promising area are outlined.
Abstract: Internet of Things (IoT) is reshaping the incumbent industry to smart industry featured with data-driven decision-making. However, intrinsic features of IoT result in a number of challenges, such as decentralization, poor interoperability, privacy, and security vulnerabilities. Blockchain technology brings the opportunities in addressing the challenges of IoT. In this paper, we investigate the integration of blockchain technology with IoT. We name such synthesis of blockchain and IoT as blockchain of things (BCoT). This paper presents an in-depth survey of BCoT and discusses the insights of this new paradigm. In particular, we first briefly introduce IoT and discuss the challenges of IoT. Then, we give an overview of blockchain technology. We next concentrate on introducing the convergence of blockchain and IoT and presenting the proposal of BCoT architecture. We further discuss the issues about using blockchain for fifth generation beyond in IoT as well as industrial applications of BCoT. Finally, we outline the open research directions in this promising area.
654 citations
Cites methods from "A Taxonomy of Blockchain-Based Syst..."
...We classify blockchain systems into three types: 1) public blockchains; 2) private blockchains; and 3) consortium (or community) blockchains [38]....
TL;DR: The operating mechanism and mainstream platforms of blockchain-enabled smart contracts are introduced, and a research framework for smart contracts based on a novel six-layer architecture is proposed.
Abstract: In recent years, the rapid development of cryptocurrencies and their underlying blockchain technology has revived Szabo’s original idea of smart contracts, i.e., computer protocols that are designed to automatically facilitate, verify, and enforce the negotiation and implementation of digital contracts without central authorities. Smart contracts can find a wide spectrum of potential application scenarios in the digital economy and intelligent industries, including financial services, management, healthcare, and Internet of Things, among others, and also have been integrated into the mainstream blockchain-based development platforms, such as Ethereum and Hyperledger. However, smart contracts are still far from mature, and major technical challenges such as security and privacy issues are still awaiting further research efforts. For instance, the most notorious case might be “The DAO Attack” in June 2016, which led to more than $50 million Ether transferred into an adversary’s account. In this paper, we strive to present a systematic and comprehensive overview of blockchain-enabled smart contracts, aiming at stimulating further research toward this emerging research area. We first introduced the operating mechanism and mainstream platforms of blockchain-enabled smart contracts, and proposed a research framework for smart contracts based on a novel six-layer architecture. Second, both the technical and legal challenges, as well as the recent research progresses, are listed. Third, we presented several typical application scenarios. Toward the end, we discussed the future development trends of smart contracts. This paper is aimed at providing helpful guidance and reference for future research efforts.
TL;DR: An established research framework is adapted to structure the insights of the current body of research on blockchain technology, the present research scope as well as disregarded topics are outlined, and multidisciplinary research approaches are sketched out.
Abstract: 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.
529 citations
Cites background or methods from "A Taxonomy of Blockchain-Based Syst..."
...First approaches introduced blockchain technology to research by providing overviews over (de)centralized consensus systems in the context of cryptocurrencies (Glaser and Bezzenberger 2015; Tschorsch and Scheuermann 2016), blockchain typologies (Walsh et al. 2016; Xu et al. 2017) or digital payment providers in general (Kazan et al....
[...]
...…et al. (2016)
Glaser and Bezzenberger (2015)
Kazan et al. (2014)
Tschorsch and Scheuermann (2016)
Walsh et al. (2016)
Watanabe et al. (2016)
Xu et al. (2017)
Zhu et al. (2016)
Hayes (2016)
Lindman et al. (2017)
Sanda and Inaba (2016)
Xu et al. (2016)
Cocco and Marchesi (2016)
Decker and…...
[...]
...…to research by providing overviews over (de)centralized consensus systems in the context of cryptocurrencies (Glaser and Bezzenberger 2015; Tschorsch and Scheuermann 2016), blockchain typologies (Walsh et al. 2016; Xu et al. 2017) or digital payment providers in general (Kazan et al. 2014)....
TL;DR: A comprehensive survey on the literature involving blockchain technology applied to smart cities, from the perspectives of smart citizen, smart healthcare, smart grid, smart transportation, supply chain management, and others is provided.
Abstract: In recent years, the rapid urbanization of world’s population causes many economic, social, and environmental problems, which affect people’s living conditions and quality of life significantly. The concept of “smart city” brings opportunities to solve these urban problems. The objectives of smart cities are to make the best use of public resources, provide high-quality services to the citizens, and improve the people’s quality of life. Information and communication technology plays an important role in the implementation of smart cities. Blockchain as an emerging technology has many good features, such as trust-free, transparency, pseudonymity, democracy, automation, decentralization, and security. These features of blockchain are helpful to improve smart city services and promote the development of smart cities. In this paper, we provide a comprehensive survey on the literature involving blockchain technology applied to smart cities. First, the related works and background knowledge are introduced. Then, we review how blockchain technology is applied in the realm of smart cities, from the perspectives of smart citizen, smart healthcare, smart grid, smart transportation, supply chain management, and others. Finally, some challenges and broader perspectives are discussed.
472 citations
Cites background from "A Taxonomy of Blockchain-Based Syst..."
...its previous block, resulting an ordered list of blocks [67]....
TL;DR: Mastering Bitcoin: Unlocking Digital Crypto-Currencies introduces Bitcoin and describes the technology behind Bitcoin and the blockchain, and Blockchain: Blueprint for a New Economy considers theoretical, philosophical, and societal impact of cryptocurrencies and blockchain technologies.
Abstract: Bitcoin is starting to come into its own as a digital currency, but the blockchain technology behind it could prove to be much more significant. This book takes you beyond the currency ("Blockchain 1.0") and smart contracts ("Blockchain 2.0") to demonstrate how the blockchain is in position to become the fifth disruptive computing paradigm after mainframes, PCs, the Internet, and mobile/social networking. Author Melanie Swan, Founder of the Institute for Blockchain Studies, explains that the blockchain is essentially a public ledger with potential as a worldwide, decentralized record for the registration, inventory, and transfer of all assetsnot just finances, but property and intangible assets such as votes, software, health data, and ideas. Topics include:Concepts, features, and functionality of Bitcoin and the blockchain Using the blockchain for automated tracking of all digital endeavors Enabling censorship? resistant organizational modelsCreating a decentralized digital repository to verify identity Possibility of cheaper, more efficient services traditionally provided by nations Blockchain for science: making better use of the data-mining network Personal health record storage, including access to ones own genomic dataOpen access academic publishing on the blockchain This book is part of an ongoing OReilly series. Mastering Bitcoin: Unlocking Digital Crypto-Currencies introduces Bitcoin and describes the technology behind Bitcoin and the blockchain. Blockchain: Blueprint for a New Economy considers theoretical, philosophical, and societal impact of cryptocurrencies and blockchain technologies.
2,277 citations
"A Taxonomy of Blockchain-Based Syst..." refers background in this paper
..., [20]), government and technical reports (e....
[...]
...The first generation of blockchains, like Bitcoin, provided a public ledger to store cryptographically-signed financial transactions [20]....
TL;DR: This paper introduces a novel quantitative framework to analyse the security and performance implications of various consensus and network parameters of PoW blockchains and devise optimal adversarial strategies for double-spending and selfish mining while taking into account real world constraints.
Abstract: Proof of Work (PoW) powered blockchains currently account for more than 90% of the total market capitalization of existing digital cryptocurrencies. Although the security provisions of Bitcoin have been thoroughly analysed, the security guarantees of variant (forked) PoW blockchains (which were instantiated with different parameters) have not received much attention in the literature. This opens the question whether existing security analysis of Bitcoin's PoW applies to other implementations which have been instantiated with different consensus and/or network parameters. In this paper, we introduce a novel quantitative framework to analyse the security and performance implications of various consensus and network parameters of PoW blockchains. Based on our framework, we devise optimal adversarial strategies for double-spending and selfish mining while taking into account real world constraints such as network propagation, different block sizes, block generation intervals, information propagation mechanism, and the impact of eclipse attacks. Our framework therefore allows us to capture existing PoW-based deployments as well as PoW blockchain variants that are instantiated with different parameters, and to objectively compare the tradeoffs between their performance and security provisions.
1,258 citations
"A Taxonomy of Blockchain-Based Syst..." refers background in this paper
...Compared with proof-of-work, proof-ofstake is more cost-efficient because much less computational power is used in mining, while latency is shorter [10]....
TL;DR: This survey unroll and structure the manyfold results and research directions of Bitcoin, and deduce the fundamental structures and insights at the core of the Bitcoin protocol and its applications.
Abstract: Besides attracting a billion dollar economy, Bitcoin revolutionized the field of digital currencies and influenced many adjacent areas. This also induced significant scientific interest. In this survey, we unroll and structure the manyfold results and research directions. We start by introducing the Bitcoin protocol and its building blocks. From there we continue to explore the design space by discussing existing contributions and results. In the process, we deduce the fundamental structures and insights at the core of the Bitcoin protocol and its applications. As we show and discuss, many key ideas are likewise applicable in various other fields, so that their impact reaches far beyond Bitcoin itself.
1,193 citations
"A Taxonomy of Blockchain-Based Syst..." refers background in this paper
...A blockchain implements a distributed ledger, which can in general verify and store any kind of transactions [22]....
TL;DR: This paper analyzes how Bitcoin uses a multi-hop broadcast to propagate transactions and blocks through the network to update the ledger replicas, and verifies the conjecture that the propagation delay in the network is the primary cause for blockchain forks.
Abstract: Bitcoin is a digital currency that unlike traditional currencies does not rely on a centralized authority. Instead Bitcoin relies on a network of volunteers that collectively implement a replicated ledger and verify transactions. In this paper we analyze how Bitcoin uses a multi-hop broadcast to propagate transactions and blocks through the network to update the ledger replicas. We then use the gathered information to verify the conjecture that the propagation delay in the network is the primary cause for blockchain forks. Blockchain forks should be avoided as they are symptomatic for inconsistencies among the replicas in the network. We then show what can be achieved by pushing the current protocol to its limit with unilateral changes to the client's behavior.
1,116 citations
"A Taxonomy of Blockchain-Based Syst..." refers background in this paper
TL;DR: In the early days of Bitcoin, the performance of its probabilistic proof-of-work (PoW) based consensus fabric, also known as blockchain, was not a major issue, and Bitcoin became a success story, despite its consensus latencies on the order of an hour and the theoretical peak throughput of only up to 7 transactions per second.
Abstract: Bitcoin cryptocurrency demonstrated the utility of global consensus across thousands of nodes, changing the world of digital transactions forever. In the early days of Bitcoin, the performance of its probabilistic proof-of-work (PoW) based consensus fabric, also known as blockchain, was not a major issue. Bitcoin became a success story, despite its consensus latencies on the order of an hour and the theoretical peak throughput of only up to 7 transactions per second.
956 citations
"A Taxonomy of Blockchain-Based Syst..." refers background in this paper
...This approach can been modified to improve scalability [24]....
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...Roughly speaking, BFT-based blockchains offers a much stronger consistency guarantee and lower latency, but for a smaller number of participants [24]....