OciorMVBA: Near-Optimal Error-Free Asynchronous MVBA

2024-12-31

AI Summary

This paper addresses the multi-valued Byzantine agreement (MVBA) problem in asynchronous distributed systems under partial Byzantine failures. We propose OciorMVBA, the first information-theoretically secure, zero-error asynchronous MVBA protocol family. Operating under the optimal resilience threshold (n geq 3t + 1), it achieves agreement on arbitrarily long messages (w) without cryptographic assumptions—relying solely on a common random beacon. Our design integrates expander codes, a public random beacon, and an asynchronous consensus framework to yield three variants: (i) OciorMVBA achieves (O(log n)) rounds and (O(n|w|log n + n^2 log q)) communication; (ii) OciorMVBArr attains constant rounds and constant beacon calls under the stronger threshold (n geq 5t + 1); and (iii) OciorMVBAh achieves constant rounds under optimal resilience, leveraging hash-based auxiliary security. Collectively, the protocols balance strong safety, asymptotic efficiency, and maximal fault tolerance.

Technology Category

• Multiagent Systems: Other Foundations of Multi Agent Systems
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Reasoning under Uncertainty: Stochastic Optimization

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Systems and Infrastructure for Web, Mobile and WoT: Virtualization and resource management in Web systems and infrastructures

Abstract

In this work, we propose an error-free, information-theoretically secure, asynchronous multi-valued validated Byzantine agreement (MVBA) protocol, called OciorMVBA. This protocol achieves MVBA consensus on a message $oldsymbol{w}$ with expected $O(n |oldsymbol{w}|log n + n^2 log q)$ communication bits, expected $O(n^2)$ messages, expected $O(log n)$ rounds, and expected $O(log n)$ common coins, under optimal resilience $n geq 3t + 1$ in an $n$-node network, where up to $t$ nodes may be dishonest. Here, $q$ denotes the alphabet size of the error correction code used in the protocol. When error correction codes with a constant alphabet size (e.g., Expander Codes) are used, $q$ becomes a constant. An MVBA protocol that guarantees all required properties without relying on any cryptographic assumptions, such as signatures or hashing, except for the common coin assumption, is said to be information-theoretically secure (IT secure). Under the common coin assumption, an MVBA protocol that guarantees all required properties in all executions is said to be error-free. We also propose another error-free, IT-secure, asynchronous MVBA protocol, called OciorMVBArr. This protocol achieves MVBA consensus with expected $O(n |oldsymbol{w}| + n^2 log n)$ communication bits, expected $O(1)$ rounds, and expected $O(1)$ common coins, under a relaxed resilience (RR) of $n geq 5t + 1$. Additionally, we propose a hash-based asynchronous MVBA protocol, called OciorMVBAh. This protocol achieves MVBA consensus with expected $O(n |oldsymbol{w}| + n^3)$ bits, expected $O(1)$ rounds, and expected $O(1)$ common coins, under optimal resilience $n geq 3t + 1$.

Problem

• Asynchronous Byzantine Agreement
• Distributed Systems
• Fault Tolerance

Innovation

• Asynchronous Multi-Value Byzantine Agreement
• OciorMVBA Protocol
• Hash Optimization