Making Speculative BFT Resilient with Trusted Monotonic Counters

Lachlan Gunn, Jian Liu, Bruno Vavala, N. Asokan

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review


Consensus mechanisms used by popular distributed ledgers are highly scalable but notoriously inefficient. Byzantine fault tolerance (BFT) protocols are efficient but far less scalable. Speculative BFT protocols such as Zyzzyva and Zyzzyva5 are efficient and scalable but require a trade-off: Zyzzyva requires only 3f+1 replicas to tolerate f faults, but even a single slow replica will make Zyzzyva fall back to more expensive non-speculative operation. Zyzzyva5 does not require a non-speculative fallback, but requires 5f+1 replicas in order to tolerate f faults. BFT variants using hardware-assisted trusted components can tolerate a greater proportion of faults, but require that every replica have this hardware.

We present SACZyzzyva, addressing these concerns: resilience to slow replicas and requiring only 3f+1 replicas, with only one replica needing an active monotonic counter at any given time. We experimentally evaluate our protocols, demonstrating low latency and high scalability. We prove that SACZyzzyva is optimally robust and that trusted components cannot increase fault tolerance unless they are present in greater than two-thirds of replicas.
Original languageEnglish
Title of host publicationIEEE 38th International Symposium on Reliable Distributed Systems : SRDS 2019, Lyon, France 1-4 October 2019
ISBN (Print)978-1-7281-4222-7
Publication statusPublished - 2019
MoE publication typeA4 Article in a conference publication
EventInternational Symposium on Reliable Distributed Systems - INSA Lyon, Campus La Doua, Lyon, France
Duration: 1 Oct 20194 Oct 2019
Conference number: 38


ConferenceInternational Symposium on Reliable Distributed Systems
Abbreviated titleSRDS
Internet address


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