Paper 2025/622

Byzantine Reliable Broadcast and Tendermint Consensus with trusted components

Abstract

Byzantine Reliable Broadcast is one of the most popular communication primitives in distributed systems. Byzantine reliable broadcast ensures that processes agree to deliver a message from an initiator, even if some processes (possibly including the initiator) are Byzantine. In asynchronous settings, it is known since the prominent work of Bracha \cite{Bracha87} that Byzantine reliable broadcast can be implemented deterministically if the total number of processes, denoted by $n$, satisfies $n \geq 3t+1$ where $t$ is an upper bound on the number of Byzantine processes. Here, we study Byzantine Reliable Broadcast when processes are equipped with \emph{trusted components}, special software or hardware designed to prevent equivocation. Our contribution is threefold. First, we show that, despite common belief, when each process is equipped with a trusted component, Bracha's algorithm still needs $n \geq 3t+1$. Second, we present a novel algorithm that uses a single trusted component (at the initiator) that implements Byzantine Reliable Asynchronous Broadcast with $n \geq 2t+1$. \yag{Lastly, building on our broadcast algorithm, we present TenderTee, a transformation of the Tendermint consensus algorithm by using trusted component, giving better Byzantine resilience. Tendertee works with $n \geq 2t+1$, where Tendermint needed $n=3t+1$.}