Hydrozoan：混合拜占庭与崩溃故障下的延迟自适应DAG共识

中文摘要 AI 辅助

基于DAG的共识协议能够实现高吞吐量，并在n=3f+1共识中达到最优的三消息延迟极限。虽然存在两延迟协议，但它们以降低容错性为代价（需要5f+1风格的委员会）或依赖牺牲DAG高吞吐量的回退机制。本文介绍了Hydrozoan，这是第一个在混合故障模型（f个拜占庭故障和c个崩溃验证者，共n=3f+c+2p+1个验证者）下具有双提交路径的DAG协议。当至多p个验证者发生故障时，领导者可在两消息延迟内提交；否则在三消息延迟内提交，无需额外消息、无需视图切换，且每轮可有多个领导者。两条路径在同一DAG上评估，采用新颖的分级间接规则来协调它们，确保每个诚实验证者达成相同决策。我们表明，在地理分布式条件下，哪条路径更快是地理属性而非协议属性，因为到达远程区域的轮次成本远高于未到达的轮次。(f,c,p)参数将快速法定人数放置在部署所需的位置，允许在两消息延迟内提交。若配置错误，Hydrozoan仍可在三消息延迟内提交：Hydrozoan在任一先触发的路径上提交。我们还提出了Optimal-Hydrozoan，一种在快速路径上多容忍一个故障的变体，这是首个匹配已知下界的构造。两种协议的安全性和活性均在Lean 4中经过机器验证。我们的地理分布式评估表明，Hydrozoan的吞吐量与Mysticeti相当，当快速法定人数适合快速区域时提交速度约快25%，否则或在过去p个故障后回退到三消息延迟，而现有的两延迟协议在此情况下会停滞。

英文摘要

DAG-based consensus protocols can achieve great throughput and the optimal three-message-delay limit for n = 3f+1 consensus. While two-delay protocols exist, they pay with reduced resilience (requiring 5f+1-style committees) or rely on fallbacks that sacrifice the DAG's high throughput. This paper introduces Hydrozoan, the first DAG protocol with a dual commit path under a hybrid fault model of f Byzantine and c crashed validators, on n = 3f+c+2p+1 validators. Leaders commit in two message delays whenever at most p validators are faulty, and in three otherwise, with no extra messages, no view changes, and multiple leaders per round. Both paths are evaluated on the same DAG, using a novel graded indirect rule to reconcile them so that every honest validator reaches the same decision. We show that under geo-distributed conditions, which path is faster is a property of geography rather than the protocol, as rounds reaching a remote region cost far more than those that do not. The (f, c, p) knobs place the fast quorum where the deployment requires it, allowing a commit in two message delays. If misconfigured, Hydrozoan can still commit in three message delays: Hydrozoan commits on whichever path fires first. We also present Optimal-Hydrozoan, a variant that tolerates one more fault on the fast path, the first construction to match the known lower bound. The safety and liveness of both protocols are machine-checked in Lean 4. Our geo-distributed evaluation shows that Hydrozoan matches Mysticeti's throughput, commits ~25% faster when the fast quorum fits fast regions, and falls back to three message delays when it does not or past p faults, where existing two-delay protocols stall.

发表机构

• The Hong Kong University of Science and Technology (Guangzhou)（香港科技大学（广州））
• Mysten Labs
• University College London (UCL)（伦敦大学学院）

机构由 AI 辅助整理，请以论文原文为准。