Byzantine agreement in the full-information model in O (log n) rounds

We present a randomized Byzantine Agreement (BA) pro tocol with an expected running time of O(log n) rounds, in a synchronous full-information network of n players. For any constant ε > 0, the constructed protocol tolerates t non-adaptive Byzantine faults, as long as n ≥ (4 + ε)t. In the full-information model, no restrictions are placed on the computational power of the faulty players or the information available to them. In particular, the faulty players may be infinitely powerful, and they can observe all communication among the honest players. This constitutes significant progress over the best known randomized BA protocol in the same setting which has a round-complexity of Θ(t/log n) rounds [9], and answers an open problem posed by Chor and Dwork [10].