[论文解读] Sidechains and interoperability

Sandra Johnson, Peter Robinson+1 more|arXiv (Cornell University)|Mar 10, 2019

Blockchain Technology Applications and Security参考文献 8被引用 36

一句话总结

本论文综述现有的侧链与跨链互操作性方法，概述关键架构（Ethereum Private Sidechains、Plasma、Polkadot、Ethereum 2.0 Sharding）以及其他提案，并提供实现与挑战的比较快照。

ABSTRACT

There appears to be an insatiable desire for spawning new bespoke blockchains to harness the functionality provided by blockchain technologies, resulting in a constant stream of blockchain start-up companies entering the market with their own unique vision and mission. Some target a particular niche market such as supply chain and financial services, while others strive to differentiate themselves from the increasingly saturated market by offering new functionality. This dynamic and constantly changing blockchain ecosystem makes it very challenging to keep abreast of all the latest breakthroughs and research. It is evident that there is also a growing desire to collaborate with others developing blockchain solutions, which brings new impetus to blockchain interoperability research. We review the strategies that some key players in the blockchain ecosystem have implemented, or are proposing to develop, to satisfy this increasing demand for cross-chain communication and transactions between sidechains. Interoperability presents a complex and challenging stumbling block to the wider uptake of blockchain technology. We find that although there is a plethora of blockchains and interoperability implementations, or proposals, at a higher level of abstraction there is only a handful of approaches. However, the way they are implemented can differ quite substantially. We present a summary of the reviews we conducted in a table for ease of comparing and contrasting.

研究动机与目标

• 评估当前跨链通信和跨侧链交易的策略。
• 总结主要互操作性项目（Ethereum Private Sidechains、Plasma、Polkadot、Ethereum 2.0 Sharding）的能力、架构和运行模型。
• 识别跨链系统的实现状态、实际挑战与设计权衡。
• 提供对比视角，帮助研究人员和从业者在选择互操作性方法时做出决策。

提出的方法

• 基于自发表、技术报告、在线文章、视频、GitHub、会议论文和期刊的文献与项目评审。
• 对每种方法的核心概念、共识模型和跨链机制进行描述性综合。
• 表格摘要（Table I）对项目进行比较以便于对比（概念性概览）。

实验结果

研究问题

• RQ1 在主要项目中观察到的侧链互操作性的主要架构模式有哪些？
• RQ2 不同方法如何实现跨链通信和跨链操作的原子性？
• RQ3 在侧链互操作性解决方案中有哪些共识、安全性和可扩展性权衡？
• RQ4 截至撰写时，关键互操作性提案的实现状态和成熟度如何？
• RQ5 跨链互操作性仍存在哪些共同挑战和未解的研究问题？

主要发现

• Ethereum Private Sidechains 使按需、短暂、私有、经许可的侧链实现能与 Ethereum MainNet 锚定并支持跨链函数调用。
• Plasma 提出通过具有不同变体（MVP、Plasma Cash 等）的子链实现扩容，并与 MainNet 的跨链网桥，数据可用性和退出属性各不相同。
• Polkadot 引入继电链(relay-chain)、平行链(parachains)和网桥(briges)，采用基于 PoS 的共识、轻客户端，以及通过结构化验证者生态系统进行跨链消息传递。
• Ethereum 2.0 分片使用 beacon 链和跨链链接以实现跨分片通信和可扩展执行，采用 PoS 模型和聚合签名。
• 其他提案（Blockchain Router、Clearmatics Ion、Metronome、NEC Hyperledger Fabric satellite chains、以及 TAST）探索跨链路由、持续执行、跨链代币和跨区块链证明。
• 总体而言，尽管有许多实现和提案，但可用的高级互操作性方法相对有限，实现选型多样，存在显著的设计权衡与尚未解决的挑战，如无限扩展、跨链验证与治理。