### Efficient Synchronous Byzantine Consensus

Ittai Abraham, Srinivas Devadas, Danny Dolev, Kartik Nayak, and Ling Ren

##### Abstract

We present new protocols for Byzantine state machine replication and Byzantine agreement in the synchronous and authenticated setting. The celebrated PBFT state machine replication protocol tolerates f Byzantine faults in an asynchronous setting using 3f +1 replicas, and has since been studied or deployed by numerous works. In this work, we improve the Byzantine fault tolerance threshold to n = 2f + 1 by utilizing a relaxed synchrony assumption. We present a synchronous state machine replication protocol that commits a decision every 3 rounds in the common case. The key challenge is to ensure quorum intersection at one honest replica. Our solution is to rely on the synchrony assumption to form a post-commit quorum of size 2f + 1, which intersects at f + 1 replicas with any pre-commit quorums of size f + 1. Our protocol also solves synchronous authenticated Byzantine agreement in expected 8 rounds. The best previous solution (Katz and Koo, 2006) requires expected 24 rounds. Our protocols may be applied to build Byzantine fault tolerant systems or improve cryptographic protocols such as cryptocurrencies when synchrony can be assumed.

Available format(s)
Publication info
Preprint. MINOR revision.
Contact author(s)
renling @ mit edu
History
2017-09-12: last of 3 revisions
See all versions
Short URL
https://ia.cr/2017/307

CC BY

BibTeX

@misc{cryptoeprint:2017/307,
author = {Ittai Abraham and Srinivas Devadas and Danny Dolev and Kartik Nayak and Ling Ren},
title = {Efficient Synchronous Byzantine Consensus},
howpublished = {Cryptology ePrint Archive, Paper 2017/307},
year = {2017},
note = {\url{https://eprint.iacr.org/2017/307}},
url = {https://eprint.iacr.org/2017/307}
}

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