[论文解读] Consensus in the Age of Blockchains

Shehar Bano, Alberto Sonnino+5 more|arXiv (Cornell University)|Nov 10, 2017

Blockchain Technology Applications and Security参考文献 83被引用 188

一句话总结

本文对区块链共识协议（PoW、PoX 及混合型）进行了全面综述，并提出一个评估框架，用以比较它们的安全性、性能和设计。

ABSTRACT

The blockchain initially gained traction in 2008 as the technology underlying bitcoin, but now has been employed in a diverse range of applications and created a global market worth over $150B as of 2017. What distinguishes blockchains from traditional distributed databases is the ability to operate in a decentralized setting without relying on a trusted third party. As such their core technical component is consensus: how to reach agreement among a group of nodes. This has been extensively studied already in the distributed systems community for closed systems, but its application to open blockchains has revitalized the field and led to a plethora of new designs. 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 systematic and comprehensive study of blockchain consensus protocols. After first discussing key themes in classical consensus protocols, we describe: first protocols based on proof-of-work (PoW), second proof-of-X (PoX) protocols that replace PoW with more energy-efficient alternatives, and third hybrid protocols that are compositions or variations of classical consensus protocols. We develop a framework to evaluate their performance, security and design properties, and use it to systematize key themes in the protocol categories described above. This evaluation leads us to identify research gaps and challenges for the community to consider in future research endeavours.

研究动机与目标

• 研究经典与区块链特定的共识，以为设计选择提供背景。
• 描绘从 PoW 到 PoX 及混合方案的演化路径。
• 建立一个统一的框架，用于评估共识协议的安全性、性能和设计属性。
• 识别研究空白与挑战，以指导区块链共识的未来工作。

提出的方法

• 对 PoW、PoX 和混合共识协议进行系统性文献综述。
• 基于核心机制将协议分类为 PoW、PoX 和混合型。
• 开发一个评估框架，重点关注安全性（一致性、抗审查、抗 DoS）、性能（吞吐量、可扩展性、延迟）以及设计考虑因素。
• 将分析建立在具有代表性的学术与权威来源及补充种子书目之上。

实验结果

研究问题

• RQ1 经典共识的关键设计主题是什么，它们如何在区块链中得到体现？
• RQ2 在安全性、性能和设计属性方面，PoW、PoX 与混合方案有何比较？
• RQ3 区块链共识存在哪些空白与挑战，未来工作应解决？
• RQ4 如何通过一个通用评估框架在不同维度上比较多样的共识设计？

主要发现

• 提供了经典共识概念如何扩展到开放区块链环境的映射。
• 引入一个在 PoW、PoX 和混合方案中适用于安全性、性能和设计的通用评估框架。
• 识别区块链共识领域广泛的研究空白与实际挑战，包括可扩展性、能源消耗与激励对齐。
• 凸显共识方法的多样性以及对严格、标准化评估模型的需求。