The Hermes BFT: Efficient Consensus in the Era of Blockchains

Mohammad M. Jalalzai is a postdoctoral researcher in Blockchain@UBC Cluster, under supervision of Dr. Chen Feng. He received his master’s degree in computer science from Technical University of Berlin in 2010 and his PhD from Louisiana State University (LSU) in 2019. His research is mainly focused on Distributed Systems, more specifically on designing, implementing and testing secure, efficient and scalable Byzantine Fault Tolerant (BFT) consensus algorithms for blockchain networks. He is also interested in the intersection of machine learning and cyber security.

The performance of partially synchronous BFT-based consensus protocols is highly dependent on the primary node. All participant nodes in the network are blocked until they receive a proposal from the primary node to begin the consensus process. Therefore, an honest but slack node (with limited bandwidth) can adversely affect the performance when selected as primary. Hermes decreases protocol dependency on the primary node and minimizes transmission delay induced by the slack primary while keeping low message complexity and latency. Hermes achieves these performance improvements by relaxing strong BFT agreement (safety) guarantees only for a specific type of Byzantine faults (also called equivocated faults). Interestingly, we show that in Hermes equivocating by a Byzantine primary is unlikely, expensive and ineffective. Therefore, the safety of Hermes is comparable to the general BFT consensus. We deployed and tested Hermes on 190 Amazon EC2 instances. Our results show that in the presence of slack nodes Hermes outperformed the state-of-the-art BFT protocol by more than 4× in terms of throughput as well as 15× in terms of latency.