Providing users' anonymity in mobile hybrid networks

We present a novel hybrid communication protocol that guarantees mobile users' anonymity against a wide-range of adversaries by exploiting the capability of handheld devices to connect to both WiFi and cellular networks. Unlike existing anonymity schemes, we consider all parties that can intercept communications between a mobile user and a server as potential privacy threats. We formally quantify the privacy exposure and the protection of our system in the presence of malicious neighboring peers, global WiFi eavesdroppers, and omniscient mobile network operators, which possibly collude to breach user's anonymity or disrupt the communication. We also describe how a micropayment scheme that suits our mobile scenario can provide incentives for peers to collaborate in the protocol. Finally, we evaluate the network overhead and attack resiliency of our protocol using a prototype implementation deployed in Emulab and Orbit, and our probabilistic model.