SoK: Consensus in the Age of Blockchains

By Shehar Bano, Alberto Sonnino, Mustafa Al-Bassam, Sarah Azouvi, Patrick McCorry, Sarah Meiklejohn, George Danezis. Conference on Advances in Financial Technologies, 2017

510 citations recorded by the source corpus.

The core technical component of blockchains is consensus: how to reach agreement among a distributed network of nodes. A plethora of blockchain consensus protocols have been proposed---ranging from new designs, to novel modifications and extensions of consensus protocols from the classical distributed systems literature. The inherent complexity of consensus protocols and their rapid and dramatic evolution makes it hard to contextualize the design landscape. We address this challenge by conducting a systematization of knowledge of blockchain consensus protocols. After first discussing key themes in classical consensus protocols, we describe: (i) protocols based on proof-of-work; (ii) proof-of-X protocols that replace proof-of-work with more energy-efficient alternatives; and (iii) hybrid protocols that are compositions or variations of classical consensus protocols. This survey is guided by a systematization framework we develop, to highlight the various building blocks of blockchain consensus design, along with a discussion on their security and performance properties. We identify research gaps and insights for the community to consider in future research endeavours.

Subfields: Computer Networks and Communications, Information Systems

View Paper: https://www.semanticscholar.org/paper/a37facbe13d9988ad32816cbcc34962235e11f62

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Citations in the corpus

A Survey on Security and Privacy Issues of Bitcoin (2017, background): “are out of the scope of our survey, hence we direct interested users to [38] [20] [39] [40] [41].”
A Vademecum on Blockchain Technologies: When, Which, and How (2019, background): “Consensus protocols in blockchains are surveyed in [29] and [30], the latter focusing on consensus evolution from the Bitcoin blockchains to the private ones.”
Non-Fungible Token (NFT): Overview, Evaluation, Opportunities and Challenges (2021, background): “Ethereum [119] further developed smart contracts in the blockchain system [84][71].”
Quantifying Blockchain Extractable Value: How dark is the forest? (2021, methodology): “For a more thorough background on blockchains, we refer the reader to several helpful SoKs [17, 18, 22].”
A Survey on Ethereum Systems Security (2019, background): “Fifth, there are surveys on blockchain consensus protocols [67, 78, 179, 186] and blockchain-based applications in IoT security [122].”
A Survey of Distributed Consensus Protocols for Blockchain Networks (2019, background): “[20] is the first well-structured survey of blockchain consensus protocols.”
FastFabric: Scaling Hyperledger Fabric to 20,000 Transactions per Second (2019, background): “• BFT consensus is being extensively studied [12] and we expect higher-throughput solutions to emerge in the next year or two.”
A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks (2018, background): “However, in spite of a few short surveys [16], [18], a comprehensive study”
RapidChain: Scaling Blockchain via Full Sharding (2018, methodology): “Unfortunately, ByzCoin’s speci cation is incomplete and the protocol is known to be vulnerable to Byzantine faults [56, 4, 9].”