International Association
for Cryptologic Research

We present Phoenixx, a round and leader based Byzantine fault tolerant consensus protocol, that operates in the partial synchrony network communications model. Phoenixx combines the three phase approach from HotStuff, with a novel \textit{Endorser Sampling}, that selects a subset of nodes, called \textit{endorsers}, to ``compress'' the opinion of the network.

Unlike traditional sampling approaches that select a subset of the network to run consensus on behalf of the network and disseminate the outcome, Phoenixx still requires participation of the whole network. The endorsers, however, assume a special role as they confirm that at least $2f+1$ validators are in agreement and issue a compressed certificate, attesting the network reached a decision. Phoenixx achieves linear communication complexity, while maintaining safety, liveness, and optimistic responsiveness, without using threshold signatures.