JUMBO: Fully Asynchronous BFT Consensus Made Truly Scalable

TL;DR

JUMBO introduces a scalable asynchronous BFT consensus protocol that reduces authenticator complexity from quadratic to quadratic order, enabling efficient operation with hundreds of nodes by leveraging aggregation and dispersal techniques.

Contribution

The paper presents JUMBO, a novel scalable asynchronous BFT consensus protocol with reduced authenticator complexity, improving performance and robustness over prior state-of-the-art methods.

Findings

JUMBO achieves $igO(n^2)$ authenticator complexity, significantly better than previous $igO(n^3)$ methods.

FIN-NG improves upon FIN and outperforms Dumbo-NG in most settings.

The protocol includes a fairness patch to prevent adversarial transaction control.

Abstract

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.