Paper 2024/774

Byzantine Reliable Broadcast with One Trusted Monotonic Counter

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 (perhaps including the initiator) are Byzantine. In asynchronous settings it is known since the prominent work of Bracha [Bracha87] that Byzantine reliable broadcast can be implemented deterministically if $n \geq 3t+1$ where $t$ is an upper bound on the number of Byzantine processes. Here, we study Byzantine Reliable Broadcast when processes are equipped with trusted execution environments (TEEs), special software or hardware designed to prevent equivocation. Our contribution is twofold. First, we show that, despite common belief, when each process is equipped with a TEE, Bracha's algorithm still needs $n \geq 3t+1$. Second, we present a novel algorithm that uses a single TEE (at the initiator) that implements Byzantine Reliable Asynchronous Broadcast with $n \geq 2t+1$.