Snowman for partial synchrony

TL;DR

This paper extends the Snowman consensus protocol used in Avalanche blockchains to operate reliably in a partially synchronous setting, allowing processes to execute sampling rounds at their own pace while maintaining probabilistic consistency.

Contribution

It introduces a modified Snowman protocol that guarantees probabilistic consistency under partial synchrony with asynchronous sampling rounds.

Findings

Ensures probabilistic consistency in partial synchrony

Allows processes to execute sampling rounds asynchronously

Maintains protocol robustness under message delays

Abstract

Snowman is the consensus protocol run by blockchains on Avalanche. Recent work established a rigorous proof of probabilistic consistency for Snowman in the \emph{synchronous} setting, under the simplifying assumption that correct processes execute sampling rounds in `lockstep'. In this paper, we describe a modification of the protocol that ensures consistency in the \emph{partially synchronous} setting, and when correct processes carry out successive sampling rounds at their own speed, with the time between sampling rounds determined by local message delays.