Recent progresses in asynchronous Byzantine fault-tolerant (BFT) consensus, e.g. Dumbo-NG (CCS' 22) and Tusk (EuroSys' 22), show promising performance through decoupling transaction dissemination and block agreement. However, when executed with a larger number $n$ of nodes, like several hundreds, they would suffer from significant degradation in performance. Their dominating scalability bottleneck is the huge authenticator complexity: each node has to multicast $\bigO(n)$ quorum certificates (QCs) and subsequently verify them for each block. This paper systematically investigates and resolves the above scalability issue. We first propose a signature-free asynchronous BFT consensus FIN-NG that adapts a recent signature-free asynchronous common subset protocol FIN (CCS' 23) into the state-of-the-art framework of concurrent broadcast and agreement. The liveness of FIN-NG relies on our non-trivial redesign of FIN's multi-valued validated Byzantine agreement towards achieving optimal quality. FIN-NG greatly improves the performance of FIN and already outperforms Dumbo-NG in most deployment settings. To further overcome the scalability limit of FIN-NG due to $\bigO(n^3)$ messages, we propose JUMBO, a scalable instantiation of Dumbo-NG, with only $\bigO(n^2)$ complexities for both authenticators and messages. We use various aggregation and dispersal techniques for QCs to significantly reduce the authenticator complexity of original Dumbo-NG implementations by up to $\bigO(n^2)$ orders. We also propose a ``fairness'' patch for JUMBO, thus preventing a flooding adversary from controlling an overwhelming portion of transactions in its output.

翻译：近期异步拜占庭容错（BFT）共识领域的进展（例如Dumbo-NG（CCS'22）和Tusk（EuroSys'22））通过解耦交易传播与区块共识展现了卓越性能。然而，当在数百个节点规模下运行时，这些协议的性能会显著下降。其核心可扩展性瓶颈在于巨大的认证复杂度：每个节点必须为每个区块多播$\bigO(n)$个仲裁证书（QC）并逐一验证。本文系统性地研究并解决了上述可扩展性问题。我们首先提出无签名异步BFT共识FIN-NG，该协议将近期无签名异步公共子集协议FIN（CCS'23）适配至当前主流的并发广播与共识框架中。FIN-NG的活性依赖于我们对FIN多值有效拜占庭协议实现最优质量的非平凡重构，该协议显著提升了FIN的性能，并在大多数部署场景中已优于Dumbo-NG。为进一步突破FIN-NG因$\bigO(n^3)$消息复杂度导致的可扩展性瓶颈，我们提出JUMBO——一种Dumbo-NG的可扩展实例化方案，其认证复杂度和消息复杂度均为$\bigO(n^2)$。我们采用多种QC聚合与分散技术，将原始Dumbo-NG实现的认证复杂度降低最多$\bigO(n^2)$数量级。此外，我们还为JUMBO设计了“公平性”补丁，以抵御洪水攻击者在其输出中控制绝大多数交易。