[2026年7月28日提出 (v1)、2026年7月29日最終改訂 (現バージョン、v2)]

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Abstract:Leader-based BFT protocols finalize through their leaders: a view whose leader is crashed or slow finalizes nothing, and the timeout that ends it admits no good setting. A conservative timeout turns every crashed leader into a long stall; an aggressive one voids the views of leaders that are merely slow. Either way the expired view is wasted, and this trade-off, not the good case, governs tail latency.
Hermes makes expired views finalize. Hermes is a two-round rotating-leader protocol for $n=5f+1$ processes under partial synchrony built on prefix consensus: votes carry values ordered by a prefix relation, and quorums require comparability rather than equality. Every process broadcasts a justified proposal at view start and casts a single vote, for the leader's proposal upon delivery or for a fallback proposal at the timeout; there are no nullify votes. A timely honest leader finalizes its full proposal in $2\delta$. Otherwise, any $n-f$ votes, which need not match, finalize the heaviest common prefix. We instantiate Hermes as a finality gadget over an available chain and over Autobahn-style multi-lane dissemination, where parent-relative delta tipcuts with explicit skips keep independent proposals comparable and sender-indexed erasure-coded amplification keeps complexity at $O(n^2\hat{m}+\lambda n^3)$ bits and $O(n^2)$ messages per view, where $\hat{m}$ is the number of concurrent dissemination lanes in Autobahn and $\lambda$ the security parameter.

Submission history

From: Alejandro Ranchal-Pedrosa [view email]
[v1] Tue, 28 Jul 2026 16:07:45 UTC (42 KB)
[v2] Wed, 29 Jul 2026 15:49:50 UTC (42 KB)