Strengthening Gossip Protocols using Protocol-Dependent Knowledge

TL;DR

This paper explores how epistemic logic can enhance gossip protocols by incorporating protocol-dependent knowledge, leading to more effective coordination in dynamic secret-sharing scenarios, though some limitations remain.

Contribution

It introduces a new operator for protocol-dependent knowledge in epistemic logic and analyzes how it can strengthen gossip protocols for better success rates.

Findings

Strengthened protocols outperform LNS in many scenarios.

No universal strengthening guarantees success in all cases.

Provides insights into epistemic coordination in distributed systems.

Abstract

Distributed dynamic gossip is a generalization of the classic telephone problem in which agents communicate to share secrets, with the additional twist that also telephone numbers are exchanged to determine who can call whom. Recent work focused on the success conditions of simple protocols such as "Learn New Secrets" (LNS) wherein an agent a may only call another agent b if a does not know b's secret. A protocol execution is successful if all agents get to know all secrets. On partial networks these protocols sometimes fail because they ignore information available to the agents that would allow for better coordination. We study how epistemic protocols for dynamic gossip can be strengthened, using epistemic logic as a simple protocol language with a new operator for protocol-dependent knowledge. We provide definitions of different strengthenings and show that they perform better than LNS, but we also prove that there is no strengthening of LNS that always terminates successfully. Together, this gives us a better picture of when and how epistemic coordination can help in the dynamic gossip problem in particular and distributed systems in general.