Brief Announcement: A Leader-free Byzantine Consensus Algorithm

Abstract

We consider the consensus problem in a partially synchronous system with Byzantine faults. In a distributed system of n processes, where each process has an initial value, Byzantine consensus is the problem of agreeing on a common value, even though some of the processes may fail in arbitrary, even malicious, ways. It is shown in [11] that — in a synchronous system — 3t + 1 processes are needed to solve the Byzantine consensus problem without signatures, where t is the maximum number of Byzantine processes. In an asynchronous system, Fischer, Lynch and Peterson [7] proved that no deterministic asynchronous consensus protocol can tolerate even a single non-Byzantine (= crash) failure. The problem can however be solved using randomization for benign and Byzantine faults. For Byzantine faults, Ben-Or [2] and Rabin [12] showed that this requires 5t + 1 processes. Later, Bracha [3] increased the resiliency of the randomized algorithm to 3t + 1.