Prioritized-MVBA: A New Approach to Design an Optimal Asynchronous Byzantine Agreement Protocol

2024-06-06

arXiv.org

AI Summary

To address the high communication overhead and multi-round latency of Multi-Value Byzantine Agreement (MVBA) in asynchronous networks, this paper proposes pMVBA—the first optimal asynchronous MVBA protocol. Methodologically, it introduces a randomized committee of size $f+1$, integrating ABBA with verifiable broadcast to achieve deterministic consensus within a single round per instance; it further employs priority-driven request aggregation and aggregate signature verification to eliminate additional computation and communication rounds. Under the standard assumption of $n = 3f + 1$ and $f < n/3$, pMVBA achieves expected $O(1)$ runtime, optimal $O(n^2)$ message complexity, and $O((l + lambda)n^2)$ communication complexity, where $l$ is the input value length and $lambda$ the security parameter. Empirical evaluation demonstrates that pMVBA significantly outperforms VABA and Dumbo-MVBA in both efficiency and scalability.

Technology Category

• Multiagent Systems: Mechanism Design
• Data Mining & Knowledge Management: Scalability, Parallel & Distributed Systems
• Reasoning under Uncertainty: Stochastic Optimization

Application Category

• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: User privacy protection in personalized systems
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

The multi-valued byzantine agreement protocol (MVBA) in the authenticated setting has been widely used as a core to design atomic broadcast and fault-tolerant state machine replication protocols in asynchronous networks. Originating from the seminal work of Cachin et al. cite{CACHIN01}, subsequent research endeavors have sought to optimize protocol efficiency in terms of communication complexity. Notable advancements following Cachin's contributions include: i) VABA cite{BYZ17}, requiring multiple protocol instances to achieve agreement on a party's request, and ii) Dumbo-MVBA cite{LU20}, employing a cryptographic asynchronous dispersal and recovery methods to manage communication complexity alongside additional computational and communication rounds overheads. Our objective is to devise an MVBA protocol that achieves agreement in each instance without extra computation and communication rounds while maintaining the optimal metrics. Central to our design approach is the introduction of the committee in the classic MVBA protocol, wherein a randomly selected subset of ($f+1$, where $n=3f+1$) parties get selected and simultaneously broadcast their requests (transactions) to gather verifiable proofs. Successive distributions of these proofs afford us the necessary properties to employ the asynchronous binary Byzantine agreement (ABBA) protocol for reaching an agreement on a selected party's requests. By integrating the committee and ABBA protocols, we devise the optimal MVBA protocol, termed pMVBA (Prioritized-MVBA). This protocol exhibits resilience to tolerate up to $lfloor frac{n}{3} floor$ Byzantine failures, with an expected runtime of $O(1)$, optimal message complexity of $O(n^2)$, and optimal communication complexity $O((l+lambda)n^2)$ .

Problem

• Designing optimal asynchronous Byzantine agreement protocol
• Achieving agreement without extra computation rounds
• Maintaining optimal communication complexity and resilience

Innovation

• Introduces committee selection in MVBA protocol
• Integrates committee with ABBA for agreement
• Achieves optimal complexity with O(1) runtime