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[Seminar] The Hermes BFT Protocol for Blockchains

Friday, December 3, 2021

11:00 am - 12:00 pm

Speaker

Prof. Konstantin “Costas” Busch
School of Computer and Cyber Sciences
Augusta University

Location

Online via MSFT Teams

Abstract

We present Hermes, a consensus protocol for permissioned blockchains suitable for controlled environments. Hermes is Byzantine Fault Tolerant (BFT) and it tolerates a constant fraction of the nodes being Byzantine (malicious). A typical approach for implementing BFT consensus is to have a primary node to propose a block and letting the remaining nodes verify the validity of the block. The performance of such consensus protocols is highly dependent on the primary node since all participant nodes are blocked until they receive a proposal from the primary node to begin the consensus process. A slack primary (with limited bandwidth), even being honest, can adversely affect the performance. Hermes decreases the protocol dependency on the primary node and minimizes transmission delay induced by the slack primary while keeping low message complexity and latency with high scalability. Hermes achieves these improvements with the use of an impetus committee for accepting new blocks, having only two phases of communication per block, and by relaxing strong BFT agreement (safety) guarantees only for a specific type of Byzantine faults called equivocated faults.

We analyzed the correctness of Hermes formally and also tested its performance on 190 AmazonEC2instances. In these tests, Hermes’s performance was comparable to the state-of-the-art BFT protocol for blockchains (when the network size is large) in the absence of slack nodes. Whereas, in the presence of slack nodes Hermes outperformed the state-of-the-art BFT protocol by more than 4.8× in terms of throughput as well as 15× in terms of latency.

About the Speaker

Konstantin “Costas” Busch obtained a B.Sc. degree in 1992 and an M.Sc. degree in 1995 both in computer science from the University of Crete, Greece. He received a Ph.D. degree in computer science from Brown University in 2000. He is a professor at the School of Computer and Cyber Sciences at Augusta University. His research interests are in the areas of distributed algorithms and data structures, design and analysis of communication algorithms, algorithmic game theory, and blockchains. He has publications in several prominent venues in algorithms and distributed computing. His research has been supported by the National Science Foundation.