Byzantine consensus with few synchronous links

Abstract

This paper tackles the consensus problem in asynchronous systems prone to byzantine failures. One way to circumvent the FLP impossibility result consists in adding synchrony assumptions (deterministic solution). In the context of crash failures (at most t processes may crash), the weakest partially synchronous system model assumes at least one correct process with outgoing links that eventually permit a bounded transmission delay with at least t neighbors (the set of neighbors may change over time). Aguilera et al. provided the main result for systems where at most t processes may exhibit a byzantine behavior. They assume a correct process with all its outgoing and incoming links eventually timely. This paper considers a system model with at least one correct process connected with x privileged neighbors with eventually timely outgoing and incoming links. In this system model, a byzantine consensus protocol is proposed. It uses authentication and assumes x ≥ 2t. © Springer-Verlag Berlin Heidelberg 2007.