International Association
for Cryptologic Research

This paper presents a collection of lessons learned from analyzing the real-world security of various Byzantine Fault Tolerant (BFT) consensus protocol implementations. Drawing upon our experience as a team of security experts who have both developed and audited BFT systems, including BA★, HotStuff variants, Paxos variants, and DAG-based algorithms like Narwhal and Bullshark, we identify and analyze a variety of security vulnerabilities discovered in the translation of theoretical protocols into real-world code. Our analysis covers a range of issues, including subtle logic errors, concurrency bugs, cryptographic vulnerabilities, and mismatches between the theoretical model and the implementation. We provide detailed case studies illustrating these vulnerabilities, discuss their potential impact, and propose mitigation strategies. This work aims to provide valuable insights for both designers and implementers of BFT consensus protocols, ultimately contributing to the development of more secure and reliable distributed systems.