VBFT: Veloce Byzantine Fault Tolerant Consensus for Blockchains

TL;DR

VBFT is a blockchain consensus protocol that achieves low-latency, two-step Byzantine fault tolerance with full safety, leader rotation, and no trusted hardware, improving on prior protocols in multiple aspects.

Contribution

VBFT introduces a two-step consensus protocol that tolerates the maximum number of Byzantine faults, supports leader rotation, and requires no trusted hardware, all while maintaining strong safety guarantees.

Findings

Achieves consensus in two communication steps with $f = (n-1)/3$ fault tolerance.

Supports leader rotation and low-cost view change.

Does not require trusted hardware, unlike some prior protocols.

Abstract

Low latency is one of the most desirable features of partially synchronous Byzantine consensus protocols. Existing low-latency protocols have achieved consensus with just two communication steps by reducing the maximum number of faults the protocol can tolerate (from $f = \frac{n-1}{3}$ to $f = \frac{n+1}{5}$), \textcolor{black}{by relaxing protocol safety guarantees}, or by using trusted hardware like Trusted Execution Environment. Furthermore, these two-step protocols don't support rotating leaders and low-cost view change (leader replacement), which are important features of many blockchain use cases. In this paper, we propose a protocol called VBFT which achieves consensus in just two communication steps without sacrificing desirable features. In particular, VBFT tolerates $f = \frac{n-1}{3}$ faults (which is the best possible), guarantees strong safety for honest leaders, and requires no trusted hardware. Moreover, VBFT supports leader rotation and low-cost view change, thereby improving prior art on multiple axes.