HotStuff-1: Linear Consensus with One-Phase Speculation
Dakai Kang, Suyash Gupta, Dahlia Malkhi, Mohammad Sadoghi
TL;DR
Addresses latency and scalability in partially synchronous Byzantine fault-tolerant consensus for blockchains and multi-party platforms. HotStuff-1 introduces speculative execution with adaptive slotting to achieve low latency while preserving linear communication complexity under up to f faults. It formalizes the prefix speculation dilemma and provides safety rules plus carry blocks and New-View/New-Slot certificates to resist tail-forking and leader-slowness, enabling early finality confirmations to clients. The approach is validated in Apache ResilientDB, showing latency reductions of up to 41.5% with slotting and 24.2% without in the no-failure case, illustrating practical, low-latency BFT suitable for financial and blockchain systems.
Abstract
This paper introduces HotStuff-1, a BFT consensus protocol that improves the latency of HotStuff-2 by two network hops while maintaining linear communication complexity against faults. Furthermore, HotStuff-1 incorporates an incentive-compatible leader rotation design that motivates leaders to propose transactions promptly. HotStuff-1 achieves a reduction of two network hops by speculatively sending clients early confirmations, after one phase of the protocol. Introducing speculation into streamlined protocols is challenging because, unlike stable-leader protocols, these protocols cannot stop the consensus and recover from failures. Thus, we identify prefix speculation dilemma in the context of streamlined protocols; HotStuff-1 is the first streamlined protocol to resolve it. HotStuff-1 embodies an additional mechanism, slotting, that thwarts delays caused by (1) rationally-incentivized leaders and (2) malicious leaders inclined to sabotage other's progress. The slotting mechanism allows leaders to dynamically drive as many decisions as allowed by network transmission delays before view timers expire, thus mitigating both threats.