An empirical study of a scalable Byzantine agreement algorithm

Abstract

A recent theoretical result by King and Saia shows that it is possible to solve the Byzantine agreement, leader election and universe reduction problems in the full information model with Õ(n3/2) total bits sent. However, this result, while theoretically interesting, is not practical due to large hidden constants. In this paper, we design a new practical algorithm, based on this theoretical result. For networks containing more than about 1,000 processors, our new algorithm sends significantly fewer bits than a well-known algorithm due to Cachin, Kursawe and Shoup. To obtain our practical algorithm, we relax the fault model compared to the model of King and Saia by (1) allowing the adversary to control only a 1/8, and not a 1/3 fraction of the processors; and (2) assuming the existence of a cryptographic bit commitment primitive. Our algorithm assumes a partially synchronous communication model, where any message sent from one honest player to another honest player needs at most Δ time steps to be received and processed by the recipient for some fixed Δ, and we assume that the clock speeds of the honest players are roughly the same. However, the clocks do not have to be synchronized (i.e., show the same time)