Revisiting EZBFT: A Decentralized Byzantine Fault Tolerant Protocol with Speculation

TL;DR

This paper critically analyzes EZBFT, revealing safety and liveness violations through simple scenarios, and discusses shortcomings in its formal specification, highlighting the need for protocol improvements.

Contribution

It identifies safety and liveness issues in EZBFT and critiques its TLA+ specification, providing insights for protocol refinement.

Findings

EZBFT exhibits safety violations in certain scenarios.

Liveness violations are demonstrated with minimal replicas.

The TLA+ specification has notable shortcomings.

Abstract

In this note, we revisit EZBFT[2] and present safety, liveness and execution consistency violations in the protocol. To demonstrate these violations, we present simple scenarios, involving only four replicas, two clients, and one or two owner changes. We also note shortcomings of the presented TLA+ specification used to model check the proposed protocol.