A protocol for anonymous short communications in social networks and its application to proximity-based services

Several innovative applications could be advantageously placed within social networks, to be effective, attractive, and pervasive. Examples of application domains that could benefit from social networks are e-democracy, e-participation, online surveys, crowdsourcing, and proximity-based services. In all the above cases, users’ anonymity could represent a considerable added value or could be even necessary to develop the service. We observe that all the above domains are characterized by the fact that only a few asynchronous messages should be exchanged. Therefore, we do not need the full communication power of anonymous communication networks, in which low-latency and connection-oriented communication should be supported. On the other hand, unlike communication networks, the threat model we have to consider assumes the presence of an adversary (represented by an honest-but-curious social network provider) able to monitor the entire flow of the exchanged messages. In this paper, we propose an anonymous communication protocol for short communications in social networks, based on a collaborative approach. The proposed solution hides from the social network provider not only the content of the messages but also the communication itself, which, per se, can result in considerable privacy leakage (think of the case of proximity testing performed between two users). This enables the implementation, within the social network, of the above-mentioned applications. To give a concrete proof of this statement, we develop a privacy-preserving proximity-based solution which provides both symmetric and asymmetric proximity testing entirely within social networks.