Communication Efficient Byzantine Agreement with Predictions

2026-05-12

AI Summary

This work addresses Byzantine consensus with predictions, aiming to drastically reduce communication overhead while tolerating an arbitrary number of incorrect predictions. By leveraging each process’s local predictions about the honest or faulty status of others, the authors design efficient protocols that avoid exchanging large volumes of prediction data. They present two algorithms—one for the unauthenticated model and another for the authenticated setting—achieving communication complexities of Õ(n²·⁵) and optimal O(n²κ), respectively, where κ denotes the security parameter. Both protocols maintain optimal round complexity and break through the previously established Ω(n³) communication lower bound, significantly outperforming existing solutions.

Abstract

In Byzantine agreement with predictions each process begins with an input value and some (unreliable) prediction bits. Recently, it has been shown that with \emph{classification predictions} -- where the predictions predict each process to be honest or faulty -- Byzantine agreement can be completed more quickly than without predictions, circumventing the traditional $Ω(f)$ round lower bound. However, existing algorithms either handle limited prediction errors or send too many messages. Moreover, they all exchange $Ω(n^3)$ bits -- enough to allow the processes to approximately agree on the classifications. In fact, it almost seemed necessary to share a significant number of prediction bits if one wanted to tolerate a high number of incorrect predictions. In this paper, we show that this high level of communication (and sharing of predictions) is not inherent by developing an unauthenticated algorithm with $\tilde{O}(n^{2.5})$ communication complexity. Furthermore, with authentication, we give an algorithm with optimal $O(n^2κ)$ communication complexity (where $κ$ is a security parameter). All of our results have optimal round complexity for any number of errors in the predictions.

Problem

• Byzantine agreement
• predictions
• communication complexity
• fault tolerance
• distributed algorithms

Innovation

• Byzantine Agreement
• Prediction-based Protocols
• Communication Complexity
• Fault Tolerance
• Distributed Algorithms