BFT-r: A proactive Byzantine Fault-Tolerant agreement with rotating coordinator and mutable blacklist mechanism

With the advent of replication-based approach for a distributed environment, a major coordination problem i.e., Consensus can be solved in the presence of some malicious replicas. Therefore, we attempt to design an agreement algorithm with proactive detection of such malicious replicas. The paper presents an algorithm BFT-r i.e., Byzantine Fault Tolerance with rotating coordinator. The basic idea is to rotate the role of the primary coordinator among all the participating replicas. Undoubtedly, the assignment of each participating replica to be primary increases the possibility of a faulty replica to be selected as primary. Therefore, in order to avoid such problem, our protocol runs a mutable blacklist mechanism in which an array of previously detected faulty replicas is maintained and propagated among the different nodes so as to avoid the decision from a faulty replica. The mutable blacklist mechanism is in line with the proactive nature of the proposed protocol. The necessary correctness proof has also been presented along with the simulation analysis. The protocol is robust and exhibits better efficiency for long-lived applications/systems.