Causality and Epistemic Reasoning in Byzantine Multi-Agent Systems

TL;DR

This paper extends the understanding of causality in distributed multi-agent systems to include Byzantine agents, providing an epistemic framework to analyze fault-tolerant communication structures.

Contribution

It introduces a novel epistemic analysis of causality in Byzantine multi-agent systems and defines a new communication structure called a multipede.

Findings

Defined the Byzantine causal cone

Introduced the multipede communication structure

Extended causality analysis to fault-tolerant settings

Abstract

Causality is an important concept both for proving impossibility results and for synthesizing efficient protocols in distributed computing. For asynchronous agents communicating over unreliable channels, causality is well studied and understood. This understanding, however, relies heavily on the assumption that agents themselves are correct and reliable. We provide the first epistemic analysis of causality in the presence of byzantine agents, i.e., agents that can deviate from their protocol and, thus, cannot be relied upon. Using our new framework for epistemic reasoning in fault-tolerant multi-agent systems, we determine the byzantine analog of the causal cone and describe a communication structure, which we call a multipede, necessary for verifying preconditions for actions in this setting.