Fire!

TL;DR

This paper provides an epistemic analysis of a Byzantine fault-tolerant primitive called FRR, detailing the knowledge conditions needed for agents to coordinate a collective action in asynchronous systems.

Contribution

It introduces the FRR primitive and characterizes the exact knowledge states required for agents to synchronize actions under Byzantine faults.

Findings

Necessary and sufficient conditions for agents to FIRE are identified.

Eventual common hope is key to achieving coordinated action.

Variations in knowledge requirements depend on agents' local preferences.

Abstract

In this paper, we provide an epistemic analysis of a simple variant of the fundamental consistent broadcasting primitive for byzantine fault-tolerant asynchronous distributed systems. Our Firing Rebels with Relay (FRR) primitive enables agents with a local preference for acting/not acting to trigger an action (FIRE) at all correct agents, in an all-or-nothing fashion. By using the epistemic reasoning framework for byzantine multi-agent systems introduced in our TARK'19 paper, we develop the necessary and sufficient state of knowledge that needs to be acquired by the agents in order to FIRE. It involves eventual common hope (a modality related to belief), which we show to be attained already by achieving eventual mutual hope in the case of FRR. We also identify subtle variations of the necessary and sufficient state of knowledge for FRR for different assumptions on the local preferences.