Byzantine Fault Tolerance
Wenbing Zhao · 2021
Early generations of algorithms for reaching Byzantine agreement and Byzantine fault tolerance are very expensive in that they incur prohibitively high runtime overhead. The Oral Message Algorithms solve the Byzantine consensus problem. The practical Byzantine fault tolerance (PBFT) algorithm tolerates Byzantine faults with certain restrictions and assumes that the faults happen independently. To ensure that a replica can authenticate a message sent by another replica, cryptographic techniques are employed. In the PBFT algorithm description, we assume that each message is protected by a public-key digital signature. This chapter discusses an optimization by replacing the digital signature, which is computationally expensive, with a message authentication code. Similar to Fast Paxos, faster Byzantine agreement can be achieved by using more replicas. Because faults are rare, it is reasonable to expect that the performance of a Byzantine fault tolerance system can be improved by speculative execution.