The Bitcoin Backbone Protocol: Analysis and Applications

【Author】 Garay, Juan; Kiayias, Aggelos; Leonardos, Nikos

【Source】JOURNAL OF THE ACM

【影响因子】2.269

【Abstract】Bitcoin is the first and most popular decentralized cryptocurrency to date. In this work, we extract and analyze the core of the Bitcoin protocol, which we term the Bitcoin backbone, and prove three of its fundamental properties which we call Common Prefix, Chain Quality, and Chain Growth in the static setting where the number of players remains fixed. Our proofs hinge on appropriate and novel assumptions on the "hashing power" of the protocol participants and their interplay with the protocol parameters and the time needed for reliable message passing between honest parties in terms of computational steps. A takeaway from our analysis is that, all else being equal, the protocol's provable tolerance in terms of the number of adversarial parties (or, equivalently, their "hashing power" in our model) decreases as the duration of a message passing round increases. Next, we propose and analyze applications that can be built "on top" of the backbone protocol, specifically focusing on Byzantine agreement (BA) and on the notion of a public transaction ledger. Regarding BA, we observe that a proposal due to Nakamoto falls short of solving it, and present a simple alternative which works assuming that the adversary's hashing power is bounded by 1/3. The public transaction ledger captures the essence of Bitcoin's operation as a cryptocurrency, in the sense that it guarantees the liveness and persistence of committed transactions. Based on this notion, we describe and analyze the Bitcoin system as well as a more elaborate BA protocol and we prove them secure assuming the adversary's hashing power is strictly less than 1/2. Instrumental to this latter result is a technique we call 2-for-1 proof-of-work (PoW) that has proven to be useful in the design of other PoW-based protocols. CCS Concepts: center dot Security and privacy -> Mathematical foundations of cryptography; Additional Key Words and Phrases: Blockchain protocols, proof of work, cryptocurrencies, consensus plications. J. ACM 71, 4, Article 25 (August 2024), 49 pages. https://doi.org/10.1145/3653445

【Keywords】

【发表时间】2024 AUG

【收录时间】2024-09-27

【文献类型】实证数据

【主题类别】

区块链技术-核心技术-共识机制