Cordial Miners: Fast and Efficient Consensus for Every Eventuality

TL;DR

The paper addresses the problem of ordering transactions in permissioned Byzantine distributed systems and argues that DAG-based consensus typically relies on Reliable Broadcast, which incurs latency and message-complexity costs. It introduces Cordial Miners, a family of RB-free Byzantine Atomic Broadcast protocols that use a blocklace, a partially ordered blockchain analogue, and a local $\tau$ function to convert the blocklace into a totally ordered sequence while excluding equivocations. Two instantiations are presented for the eventual synchrony (ES) and asynchronous models, achieving latencies of $4.5$ rounds expected (good-case $3$) in ES and $7.5$ rounds expected (good-case $5$) in the asynchronous setting, with amortized worst-case message complexity $O(n^2)$ and good-case $O(n)$. By avoiding Reliable Broadcast and leveraging the blocklace with $\tau$, Cordial Miners reduces end-to-end latency in common cases while still handling equivocation without extra communication, offering a practical RB-free solution for permissioned ledgers.

Abstract

Cordial Miners are a family of efficient Byzantine Atomic Broadcast protocols, with instances for asynchrony and eventual synchrony. They improve the latency of state-of-the-art DAG-based protocols by almost 2X and achieve optimal good-case complexity of O(n) by forgoing Reliable Broadcast as a building block. Rather, Cordial Miners use the blocklace -- a partially-ordered counterpart of the totally-ordered blockchain data structure -- to implement the three algorithmic components of consensus: Dissemination, equivocation-exclusion, and ordering.

Theorems & Definitions (1)

• Definition 1: Safety and Liveness of an Ordering Consensus Protocol