Protocols for Fault Identifcation in Partially Known Networks
Abstract
We consider a group of players who perform tasks repeatedly. The players are nodes of a communication network and observe their neighbor's actions. Players have partial knowledge of the network and only know their set of neighbors. We study the existence of communication protocols that identify faults: whenever a player chooses a faulty action, the communication protocol publicly reveals the identity of the faulty player. We consider two setups. In the first one, players do not share authentication keys. We show that existence of a protocol that indentifies faults is equivalent to the 2-vertex-connectedness of the network: no single vertex deletion disconnects the graph. In the second setup, we allow players to share authentication keys. We show that existence of a distribution of the keys and of a protocol that indentifies faults is equivalent to the 2-edge-connectedness of the network: no single edge deletion disconnects the graph. We give applications to the implementation of socially optimal outcomes in repeated games.