Embedding a Deterministic BFT Protocol in a Block DAG

Abstract

This work formalizes the structure and protocols underlying recent distributed systems leveraging block DAGs, which are essentially encoding Lamport's happened-before relations between blocks, as their core network primitives. We then present an embedding of any deterministic Byzantine fault tolerant protocol $\mathcal{P}$ to employ a block DAG for interpreting interactions between servers. Our main theorem proves that this embedding maintains all safety and liveness properties of $\mathcal{P}$. Technically, our theorem is based on the insight that a block DAG merely acts as an efficient reliable point-to-point channel between instances of P while also using $\mathcal{P}$ for efficient message compression.