  The HotStuff protocol is a breakthrough in Byzantine Fault Tolerant (BFT)
consensus that enjoys both responsiveness and linear view change. It creatively
adds an additional round to classic BFT protocols (like PBFT) using two rounds.
This brings us to an interesting question: Is this additional round really
necessary in practice? In this paper, we answer this question by designing a
new two-round BFT protocol called Fast-HotStuff, which enjoys responsiveness
and efficient view change that is comparable to linear view change in terms of
performance. Compared to (three-round) HotStuff, Fast-HotStuff has lower
latency and is more robust against performance attacks that HotStuff is
susceptible to.
