Short Paper: Accountable Safety Implies Finality

TL;DR

This paper demonstrates that in Byzantine-fault tolerant consensus protocols, accountable safety guarantees can ensure finality, unifying previous separate results and advancing blockchain safety guarantees.

Contribution

It proves that accountable safety implies finality, providing a unified understanding of safety properties in BFT consensus protocols.

Findings

Accountable safety guarantees can ensure finality in BFT protocols.

Unification of previous separate results on safety properties.

Advancement in blockchain consensus safety guarantees.

Abstract

Motivated by proof-of-stake (PoS) blockchains such as Ethereum, two key desiderata have recently been studied for Byzantine-fault tolerant (BFT) state-machine replication (SMR) consensus protocols: Finality means that the protocol retains consistency, as long as less than a certain fraction of validators are malicious, even in partially-synchronous environments that allow for temporary violations of assumed network delay bounds. Accountable safety means that in any case of inconsistency, a certain fraction of validators can be identified to have provably violated the protocol. Earlier works have developed impossibility results and protocol constructions for these properties separately. We show that accountable safety implies finality, thereby unifying earlier results.