A Game-Theoretic Approach to Anonymous Networking

Anonymous wireless networking is studied when an adversary monitors the transmission timing of an unknown subset of the network nodes. For a desired quality of service (QoS), as measured by network throughput, the problem of maximizing anonymity is investigated from a game-theoretic perspective. Quantifying anonymity using conditional entropy of the routes given the adversary's observation, the problem of optimizing anonymity is posed as a two-player zero-sum game between the network designer and the adversary: The task of the adversary is to choose a subset of nodes to monitor so that anonymity of routes is minimum, whereas the task of the network designer is to maximize anonymity by choosing a subset of nodes to evade flow detection by generating independent transmission schedules. In this two-player game, it is shown that a unique saddle-point equilibrium exists for a general category of finite networks. At the saddle point, the strategy of the network designer is to ensure that any subset of nodes monitored by the adversary reveals an identical amount of information about the routes. For a specific class of parallel relay networks, the theory is applied to study the optimal performance tradeoffs and equilibrium strategies. In particular, when the nodes employ transmitter-directed signaling, the tradeoff between throughput and anonymity is characterized analytically as a function of the network parameters and the fraction of nodes monitored. The results are applied to study the relationships between anonymity, the fraction of monitored relays, and the fraction of hidden relays in large networks.