[论文解读] Settling Payments Fast and Private: Efficient Decentralized Routing for Path-Based Transactions

Stefanie Roos, Pedro Moreno-Sánchez+2 more|arXiv (Cornell University)|Sep 17, 2017

Blockchain Technology Applications and Security被引用 5

一句话总结

本文提出 SpeedyMurmurs，一种用于基于路径的交易（PBT）网络的去中心化、隐私保护型路由算法，采用基于嵌入的路径发现与按需稳定机制。与以往方法相比，其稳定化开销降低多达两个数量级，路由开销减少超过50%，同时保持高成功率和强隐私保障。

ABSTRACT

Path-based transaction (PBT) networks, which settle payments from one user to another via a path of intermediaries, are a growing area of research. They overcome the scalability and privacy issues in cryptocurrencies like Bitcoin and Ethereum by replacing expensive and slow on-chain blockchain operations with inexpensive and fast off-chain transfers. In the form of credit networks such as Ripple and Stellar, they also enable low-price real-time gross settlements across different currencies. For example, SilentWhsipers is a recently proposed fully distributed credit network relying on path-based transactions for secure and in particular private payments without a public ledger. At the core of a decentralized PBT network is a routing algorithm that discovers transaction paths between payer and payee. During the last year, a number of routing algorithms have been proposed. However, the existing ad hoc efforts lack either efficiency or privacy. In this work, we first identify several efficiency concerns in SilentWhsipers. Armed with this knowledge, we design and evaluate SpeedyMurmurs, a novel routing algorithm for decentralized PBT networks using efficient and flexible embedding-based path discovery and on-demand efficient stabilization to handle the dynamics of a PBT network. Our simulation study, based on real-world data from the currently deployed Ripple credit network, indicates that SpeedyMurmurs reduces the overhead of stabilization by up to two orders of magnitude and the overhead of routing a transaction by more than a factor of two. Furthermore, using SpeedyMurmurs maintains at least the same success ratio as decentralized landmark routing, while providing lower delays. Finally, SpeedyMurmurs achieves key privacy goals for routing in PBT networks.

研究动机与目标

• 解决现有去中心化基于路径的交易（PBT）网络路由算法在效率、隐私和可扩展性方面的综合不足问题。
• 克服基于地标路由（如 SilentWhispers）和集中式方案（如 Canal、PrivPay）中存在的隐私泄露问题，后者会暴露交易金额、身份或链路权重。
• 设计一种去中心化的路由算法，在保持高成功率的同时最小化路由与稳定化开销。
• 确保对强大网络攻击者具备强隐私保障——包括金额隐私与发送方/接收方隐私。
• 实现真实 PBT 网络（如 Lightning Network、Raiden 及跨区块链系统）中的实际部署。

提出的方法

• 采用基于嵌入的路径发现机制，利用节点和链路的低维向量表示，高效计算发送方与接收方之间的候选路径。
• 引入按需稳定机制，仅在必要时动态更新路由信息，相比周期性更新显著降低消息开销。
• 采用灵活且局部化的更新方式传播通道余额变化，避免网络洪泛，提升可扩展性与效率。
• 通过避免使用中心化服务器或可信硬件，维持去中心化架构，确保系统韧性与强隐私保障。
• 集成隐私保护技术，隐藏交易金额与身份信息，防止中间节点与外部观察者获取。
• 利用 Ripple 信用网络的真实数据进行仿真与性能评估，模拟真实网络动态下的表现。

实验结果

研究问题

• RQ1 去中心化路由算法是否能在不依赖中心化实体或公共区块链的前提下，同时实现高效率与强隐私保护？
• RQ2 基于嵌入的路径发现与基于地标或链路状态的路由相比，在路由开销与成功率方面表现如何？
• RQ3 在动态 PBT 网络中，按需稳定机制相比周期性稳定机制，能在多大程度上降低网络开销？
• RQ4 所提出的算法是否能在保护金额隐私与发送方/接收方隐私的同时，维持高交易成功率？
• RQ5 在真实网络动态与频繁通道余额更新下，该算法的可扩展性如何？

主要发现

• 与现有去中心化路由方法相比，SpeedyMurmurs 将稳定化开销降低了多达两个数量级。
• 路由开销相比最先进方法减少超过两倍，同时保持至少相同的交易成功率。
• SpeedyMurmurs 实现了强隐私保障，包括金额隐私与发送方/接收方隐私，即使面对强大网络攻击者亦成立。
• 该算法在延迟与效率方面均优于基于地标路由（如 SilentWhispers），同时保持隐私保护能力。
• 在动态网络阶段，按需稳定机制比周期性稳定机制更具效率，表明未来可采用自适应稳定策略。
• 基于真实 Ripple 网络数据的仿真结果证实，该算法在真实交易负载下具备有效性与可扩展性。