Brief Announcement: A Leader-free Byzantine Consensus Algorithm
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  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  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  and Rabin  showed that this requires 5t + 1 processes. Later, Bracha  increased the resiliency of the randomized algorithm to 3t + 1.
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