Efficient dynamic-committee BFT consensus based on HotStuff

Traditional Byzantine Fault Tolerant (BFT) consensus protocols are designed for fixed groups and are aimed to ensure the consistency of states among the replicas in distributed systems. Dynamic-committee BFT consensus protocols allow replicas to dynamically join and leave the system, enhancing the robustness and flexibility of distributed systems. However, the state-of-the-art dynamic BFT consensus protocol in partially synchronous networks suffers from an O(n4) worst-case authenticator complexity, where n is the number of replicas. In comparison, existing static BFT protocols have achieved O(n2) worst-case complexity. Hence, there is a performance gap between static and dynamic BFT consensus protocols. In this paper, we propose an efficient dynamic-committee BFT consensus protocol based on HotStuff, enabling member churn with minimal impact on performance metrics. With our improved committee reconfiguration technique, we reduce the worst-case authenticator complexity of dynamic BFT consensus from O(n4) to O(n3), while maintaining the best-case complexity of O(n2). Besides, our protocol inherits the pipelined property from HotStuff, thus achieving a higher throughput. Experimental results show that our protocol has a peak throughput 4.2–7.6x as high as that of BFT-SMaRt, exhibiting a better scalability. The latency of join requests increases by 25%–60% compared to regular requests, while the latency of leave requests shows no significant difference from regular requests.