Proactive Byzantine Quorum Systems

Byzantine Quorum Systems is a replication technique used to ensure availability and consistency of replicates data even in presence of arbitrary faults. This paper presents a Byzantine Quorum Systems protocol that provides atomic semantics despite the existence of Byzantine clients and servers. Moreover, this protocol is integrated with a protocol for proactive recovery of servers. In that way, the system tolerates any number of failures during its lifetime, since no more than f out of n servers fail during a small interval of time between recoveries. All solutions proposed in this paper can be used on asynchronous systems, which requires no time assumptions. The proposed quorum system read and write protocols have been implemented and their efficiency is demonstrated through some experiments carried out in the Emulab platform.