The Istanbul BFT Consensus Algorithm

TL;DR

The paper introduces IBFT, a Byzantine fault-tolerant consensus algorithm for blockchains that ensures safety without timing assumptions and achieves efficient consensus under partial synchrony.

Contribution

It presents IBFT, a simple, deterministic, leader-based Byzantine fault-tolerant consensus algorithm optimized for blockchain state machine replication.

Findings

Achieves termination in three message delays during synchrony

Tolerates up to f faulty processes out of n

Has an O(n^2) total communication complexity

Abstract

This paper presents IBFT, a simple and elegant Byzantine fault-tolerant consensus algorithm that is used to implement state machine replication in the \emph{Quorum} blockchain. IBFT assumes a partially synchronous communication model, where safety does not depend on any timing assumptions and only liveness depends on periods of synchrony. The algorithm is deterministic, leader-based, and optimally resilient - tolerating $f$ faulty processes out of $n$, where $n \geq 3f+1$. During periods of good communication, IBFT achieves termination in three message delays and has $O(n^2)$ total communication complexity.