arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2009.09480cs.DCcs.CRcs.DS
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区块链协议安全性分析的通用框架

A General Framework for the Security Analysis of Blockchain Protocols

Andrew Lewis-Pye, Tim Roughgarden

摘要:

区块链协议在基本方面有所不同,包括选择用户生成区块的机制(例如,工作证明对权益证明)和建立共识的方法(例如,最长链规则与拜占庭容错(BFT)启发的协议)。这些根本性的差异阻碍了不同类别的区块链协议之间的“苹果对苹果”的比较,反过来,也阻碍了理论的发展,以正式讨论它们的相对优点。本文提出了一种简约的抽象,足以捕获和比较许多著名的无权限区块链协议的属性,同时捕获工作量证明(PoW)和权益证明(PoS)协议以及最长链类型和BFT类型协议的基本属性。我们的框架黑盒的用户选择过程的精确机制,使我们能够隔离的选择过程中的属性是重要的协议设计。我们证明了我们的一般框架的实用性与几个具体的结果:1。我们证明了一个CAP型不可能性定理断言,一个未知的参与水平的活性排除了部分同步设置中的安全性。2.深入研究部分同步设置,我们证明了安全的一个必要和充分条件是生产的“证书”,这意味着块确认的独立证明。3.限制到同步设置,我们证明了具有已知参与水平的典型协议(包括最长链型PoS协议)可以适用于提供证书,但具有未知参与水平的协议则不能。4.最后,我们使用我们的框架来阐明区块链安全分析的模块化两步方法,该方法有效地将无许可情况减少到许可情况。

英文摘要:

Blockchain protocols differ in fundamental ways, including the mechanics of selecting users to produce blocks (e.g., proof-of-work vs. proof-of-stake) and the method to establish consensus (e.g., longest chain rules vs. Byzantine fault-tolerant (BFT) inspired protocols). These fundamental differences have hindered "apples-to-apples" comparisons between different categories of blockchain protocols and, in turn, the development of theory to formally discuss their relative merits. This paper presents a parsimonious abstraction sufficient for capturing and comparing properties of many well-known permissionless blockchain protocols, simultaneously capturing essential properties of both proof-of-work (PoW) and proof-of-stake (PoS) protocols, and of both longest-chain-type and BFT-type protocols. Our framework blackboxes the precise mechanics of the user selection process, allowing us to isolate the properties of the selection process that are significant for protocol design. We demonstrate the utility of our general framework with several concrete results: 1. We prove a CAP-type impossibility theorem asserting that liveness with an unknown level of participation rules out security in a partially synchronous setting. 2. Delving deeper into the partially synchronous setting, we prove that a necessary and sufficient condition for security is the production of "certificates," meaning stand-alone proofs of block confirmation. 3. Restricting to synchronous settings, we prove that typical protocols with a known level of participation (including longest chain-type PoS protocols) can be adapted to provide certificates, but those with an unknown level of participation cannot. 4. Finally, we use our framework to articulate a modular two-step approach to blockchain security analysis that effectively reduces the permissionless case to the permissioned case.

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