Gorilla: Safe Permissionless Byzantine Consensus

TL;DR

Gorilla Sandglass is a novel permissionless Byzantine consensus protocol that guarantees deterministic agreement and termination with probability 1 in a synchronous model, improving upon probabilistic guarantees of previous protocols.

Contribution

It introduces Gorilla Sandglass, the first protocol to achieve Byzantine fault tolerance with deterministic guarantees in a permissionless setting within a synchronous model.

Findings

Gorilla Sandglass guarantees agreement and termination with probability 1.

The protocol maps executions to Sandglass to prove correctness.

It operates in a permissionless, synchronous environment.

Abstract

Nakamoto's consensus protocol works in a permissionless model and tolerates Byzantine failures, but only offers probabilistic agreement. Recently, the Sandglass protocol has shown such weaker guarantees are not a necessary consequence of a permissionless model; yet, Sandglass only tolerates benign failures, and operates in an unconventional partially synchronous model. We present Gorilla Sandglass, the first Byzantine tolerant consensus protocol to guarantee, in the same synchronous model adopted by Nakamoto, deterministic agreement and termination with probability 1 in a permissionless setting. We prove the correctness of Gorilla by mapping executions that would violate agreement or termination in Gorilla to executions in Sandglass, where we know such violations are impossible. Establishing termination proves particularly interesting, as the mapping requires reasoning about infinite executions and their probabilities.