## Cryptology ePrint Archive: Report 2019/270

Sync HotStuff: Simple and Practical Synchronous State Machine Replication

Ittai Abraham and Dahlia Malkhi and Kartik Nayak and Ling Ren and Maofan Yin

Abstract: Synchronous solutions for Byzantine Fault Tolerance (BFT) can tolerate up to minority faults. In this work, we present Sync HotStuff, a surprisingly simple and intuitive synchronous BFT solution that achieves consensus with a latency of $2\Delta$ in the steady state (where $\Delta$ is a synchronous message delay upper bound). In addition, Sync HotStuff ensures safety in a weaker synchronous model in which the synchrony assumption does not have to hold for all replicas all the time. Moreover, Sync HotStuff has optimistic responsiveness, i.e., it advances at network speed when less than one-quarter of the replicas are not responding. Borrowing from practical partially synchronous BFT solutions, Sync HotStuff has a two-phase leader-based structure, and has been fully prototyped under the standard synchrony assumption. When tolerating a single fault, Sync HotStuff achieves a throughput of over 280 Kops/sec under typical network performance, which is comparable to the best known partially synchronous solution.

Category / Keywords: Distributed computing, blockchains, consensus protocols, SMR, Synchrony

Date: received 6 Mar 2019, last revised 4 May 2020

Contact author: kartik1507 at gmail com

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2019/270

[ Cryptology ePrint archive ]