Paper 2023/1211 Original: eprint.iacr.org/2023/1211 ↗
Optimal Flexible Consensus and its Application to Ethereum
Abstract
Classic BFT consensus protocols guarantee safety and liveness for all clients if fewer than one-third of replicas are faulty. However, in applications such as high-value payments, some clients may want to prioritize safety over liveness. Flexible consensus allows each client to opt for a higher safety resilience, albeit at the expense of reduced liveness resilience. We present the first construction that allows optimal safety-liveness tradeoff for every client simultaneously. This construction is modular and is realized as an add-on applied on top of an existing consensus protocol. The add-on consists of an additional round of voting and permanent locking done by the replicas, to sidestep a sub-optimal quorum-intersection-based constraint present in previous solutions. We adapt our construction to the existing Ethereum protocol to derive optimal flexible confirmation rules that clients can adopt unilaterally without requiring system-wide changes. This is possible because existing Ethereum protocol features can double as the extra voting and locking. We demonstrate an implementation using Ethereum's consensus API.
Metadata
- Available format(s)
PDF- Category
- Cryptographic protocols
- Publication info
- Preprint.
- History
- 2023-12-06: last updated
- 2023-08-10: published
- Short URL
- https://ia.cr/2023/1211
- License
- https://creativecommons.org/licenses/by/4.0/
BibTeX
@misc{cryptoeprint:2023/1211,
author = {Joachim Neu and Srivatsan Sridhar and Lei Yang and David Tse},
title = {Optimal Flexible Consensus and its Application to Ethereum},
howpublished = {Cryptology {ePrint} Archive, Paper 2023/1211},
year = {2023},
url = {https://eprint.iacr.org/2023/1211}
}