Majorum: Ebb-and-Flow Consensus with Dynamic Quorums

TL;DR

Majorum is a novel consensus protocol combining dynamic availability with a finality mechanism, enabling fast block finalization under optimistic conditions while maintaining safety during network issues.

Contribution

It introduces Majorum, an ebb-and-flow construction that enhances quorum-based protocols with rapid finality capabilities in optimistic scenarios.

Findings

Finalizes blocks in as few as three slots under optimistic conditions

Requires only a single voting phase per slot for finalization

Maintains safety during network partitions and asynchrony

Abstract

Dynamic availability is the ability of a consensus protocol to remain live despite honest participants going offline and later rejoining. A well-known limitation is that dynamically available protocols, on their own, cannot provide strong safety guarantees during network partitions or extended asynchrony. Ebb-and-flow protocols [SP21] address this by combining a dynamically available protocol with a partially synchronous finality protocol that irrevocably finalizes a prefix. We present Majorum, an ebb-and-flow construction whose dynamically available component builds on a quorum-based protocol (TOB-SVD). Under optimistic conditions, Majorum finalizes blocks in as few as three slots while requiring only a single voting phase per slot. In particular, when conditions remain favourable, each slot finalizes the next block extending the previously finalized one.