Kudzu: Fast and Simple High-Throughput BFT

2025-05-13

AI Summary

This paper addresses three key challenges in Byzantine Fault-Tolerant (BFT) atomic broadcast: limited throughput, leader bandwidth bottlenecks, and high finality latency. To tackle these, we propose Kudzu—a novel BFT protocol. Methodologically, Kudzu introduces the first lightweight two-round fast path that achieves strong fault tolerance without relying on progress certificates, view changes, or speculative execution. It tolerates *f* Byzantine faults and *p* slow nodes in a system of *n = 3f + 2p + 1* replicas. Key mechanisms include erasure-coded block dissemination, simplified state synchronization, and deterministic replica rotation—collectively balancing bandwidth load across all replicas. Evaluation demonstrates that Kudzu significantly improves throughput, eliminates the leader bottleneck, and maintains state-of-the-art performance with low latency under diverse failure scenarios.

Technology Category

• Data Mining & Knowledge Management: Scalability, Parallel & Distributed Systems
• Search and Optimization: Distributed Search
• Machine Learning: Online Learning & Bandits

Application Category

• Security and Privacy: Large-scale security measurements
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Responsible Web: Data and user privacy-enhancing technologies for the Web

Abstract

We present Kudzu, a high-throughput atomic broadcast protocol with an integrated fast path. Our contribution is based on the combination of two lines of work. Firstly, our protocol achieves finality in just two rounds of communication if all but $p$ out of $n = 3f + 2p + 1$ participating replicas behave correctly, where $f$ is the number of Byzantine faults that are tolerated. Due to the seamless integration of the fast path, even in the presence of more than $p$ faults, our protocol maintains state-of-the-art characteristics. Secondly, our protocol utilizes the bandwidth of participating replicas in a balanced way, alleviating the bottleneck at the leader, and thus enabling high throughput. This is achieved by disseminating blocks using erasure codes. Despite combining a novel set of advantages, Kudzu is remarkably simple: intricacies such as progress certificates, complex view changes, and speculative execution are avoided.

Problem

• Achieves fast finality in two communication rounds
• Balances bandwidth usage to enable high throughput
• Simplifies protocol design by avoiding complex mechanisms

Innovation

• Two-round finality with fault tolerance
• Balanced bandwidth usage via erasure codes
• Simplified design avoiding complex mechanisms