HotStuff-2: Optimal Two-Phase Responsive BFT - Dahlia Malkhi

Dahlia Malkhi (Chainlink Labs), Kartik Nayak (Duke University)

In this paper, we observe that it is possible to solve partially-synchronous BFT and simultaneously achieves 𝑂(𝑛2) worst-case communication, optimistically linear communication, a two-phase commit regime within a view, and optimistic responsiveness. Prior work falls short in achieving one or more of these properties, e.g., the most closely related work, HotStuff, requires a three-phase view while achieving all other properties. We demonstrate that these properties are achievable through a two-phase HotStuff variant named HotStuff-2. The quest for two-phase HotStuff variants that achieve all the above desirable properties has been long, producing a series of results that are yet sub-optimal and, at the same time, are based on somewhat heavy hammers. HotStuff-2 demonstrates that none of these are necessary: HotStuff-2 is remarkably simple, adding no substantive complexity to the original HotStuff protocol. The main takeaway is that two phases are enough for BFT after all.

ConsensusDays 23 Session 2.3- Latency Optimisation
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Playlist: ConsensusDays 23