COMBFT: Conflicting-Order-Match based Byzantine Fault Tolerance Protocol with High Efficiency and Robustness

Byzantine Fault-Tolerant (BFT) state machine replication protocol is an important building block for highly available distributed computing. This paper presents COMBFT, a BFT protocol that achieves both efficiency and robustness simultaneously. The major novelty of COMBFT lies in Conflicting-Order-Match (COM), a new request ordering mechanism that uses a new way to select the available sequence number for requests, and detects the possible malicious primary early. COM assigns sequence number based on request interference, and requires both primary and backup nodes to conduct request ordering, which can greatly reduce the impact of malicious primary and clients. When the backup suspects the primary may be malicious, it triggers an efficient commit protocol with two phases (i.e., suspect phase and commit phase) to further confirm whether the primary is malicious, and commit the request. The performance of COMBFT is evaluated via simulations and the results illustrate the outstanding performance of COMBFT in terms of throughput, latency and fault scalability.