Janus: Enhancing Asynchronous Common Subset with Trusted Hardware

Asynchronous common subset (ACS) has been extensively studied since the asynchronous Byzantine fault tolerance (BFT) framework was introduced by Ben-Or, Kemler, and Rabin (BKR). The line of work (i.e., HoneyBadgerBFT, BEAT, EPIC) uses parallel reliable broadcast (RBC) and asynchronous binary agreement (ABA) instances to reach an agreement on a subset of proposed transactions.In this paper, we further progress the BKR paradigm by presenting Janus, the first hybrid ACS protocol leveraging trusted hardware components. Janus is the first ACS protocol that tolerates a minority of Byzantine processes and that has $\mathcal{O}\left( {{n^2}} \right)$ message complexity. Supported by trusted hardware components, we introduce a provable broadcast primitive to replace RBC, and develop a resilient binary agreement protocol. Messages for concurrent instances of agreement are aggregated into vectors. Our experimental results demonstrate significant performance improvements over predominant ACS constructions with a 92%+ increase compared to HoneyBadgerBFT and a 47%+ increase compared to BEAT. Additionally, we provide a comparison with open-source hybrid BFT protocols that operate under a partially synchronous network, highlighting the performance enhancement compared to previous hybrid protocols that also tolerate the Byzantine minority (e.g., MinBFT and Damysus, by 49%+).