A lightweight BFT consensus protocol for blockchains

TL;DR

This paper introduces a lightweight, customizable Byzantine fault tolerant consensus framework for blockchains, exemplified by Lisk-BFT, ensuring safety and liveness under specific validator fault assumptions.

Contribution

The paper presents a general, adaptable BFT consensus framework and implements Lisk-BFT, a practical protocol compatible with existing blockchain systems requiring minimal modifications.

Findings

Proves safety with less than 1/3 Byzantine validators.

Demonstrates liveness with less than 1/3 crashing validators.

Integrates seamlessly with existing block proposal mechanisms.

Abstract

We present a general consensus framework that allows to easily introduce a customizable Byzantine fault tolerant consensus algorithm to an existing (Delegated) Proof-of-Stake blockchain. We prove the safety of the protocol under the assumption that less than 1/3 of the validators are Byzantine. The framework further allows for consensus participants to choose subjective decision thresholds in order to obtain safety even in the case of a larger proportion of Byzantine validators. Moreover, the liveness of the protocol is shown if less than 1/3 of the validators crash. Based on the framework, we introduce Lisk-BFT, a Byzantine fault tolerant consensus algorithm for the Lisk ecosystem. Lisk-BFT integrates with the existing block proposal mechanism, requires only two additional integers in blocks and no additional messages. The protocol is simple and provides safety in the case of static validators if less than 1/3 of the validators are Byzantine. For the case of dynamically changing validators, we prove the safety of the protocol assuming a bound on the number of Byzantine validators and the number of honest validators that can change at one time. We further show the liveness of the Lisk-BFT protocol for less than 1/3 crashing validators.