Game Theoretic Model of Censorship Resistance Andrei Serjantov University of Cambridge Computer Laboratory

Scenario P2P censorship resistant network Traditional model: secure or insecure –Does not explain the fact that holiday photos are not “censored” –Hence, build an economic model: Attacker derives utility from censoring, publisher derives utility from the fact that his document is available The conflict between the publisher and the cesnsor

Model Network of size n Publisher publishes to number of nodes d, at a cost c(d) Attacker attacks x nodes, at a cost c(x) If no copies are available, attacker get U If one or more copies is available, publisher gets U’

Results If attacker’s cost is linear, no Nash Equilibria in pure strategies. If the cost is c(x) = x α, then there are Nash equilibria at d<α Meaning: publisher publishes to some nodes, some nodes get attacked. This challenges the traditional model of insecure