Majorum: Ebb-and-Flow Consensus with Dynamic Quorums

2026-01-07

arXiv.org

AI Summary

This work addresses the challenge of achieving both liveness and strong safety in consensus protocols under conditions of dynamic participant availability and network asynchrony. The authors propose Majorum, a novel consensus architecture that integrates a quorum-based TOB-SVD protocol with a partially synchronous finality mechanism to realize an ebb-and-flow consensus model. This design enables participants to freely go offline and reconnect while ensuring strong safety through prefix immutability. Under optimistic network conditions, Majorum achieves efficient finality with single-round voting and confirms one block every three slots, substantially improving system throughput and responsiveness without compromising security guarantees.

Technology Category

• Multiagent Systems: Mechanism Design
• Natural Language Processing: Safety and Robustness
• Search and Optimization: Distributed Search

Application Category

• Security and Privacy: Large-scale security measurements
• Responsible Web: Consent frameworks and practices on the web
• Systems and Infrastructure for Web, Mobile and WoT: Decentralized Web and Fediverse systems

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.

Problem

• dynamic availability
• consensus protocol
• network partition
• strong safety
• asynchrony

Innovation

• ebb-and-flow consensus
• dynamic availability
• quorum-based protocol
• finality
• partial synchrony