SamaritanCloud: Secure and scalable infrastructure for enabling location-based services

With the maturation of online social networks (OSNs), people have begun to form online communities and look for assistance at a particular place and time from people they only know virtually. However, seeking for such help on existing OSN infrastructures has some disadvantages including loss of privacy (in terms of both location as well as the nature of the help sought) and high response times. In this paper we propose SamaritanCloud, a scalable infrastructure that enables a group of mobile and geographically-dispersed personal computing devices to form a cloud for the purpose of privately sharing relevant locality-specific information. From a technical standpoint our main contribution is to show that only additive homorphic encryption is sufficient to compute nearness in a cryptographically secure and scalable way in a distributed setting. This allows us to harness the benefit of linear match time while guaranteeing the locational privacy of the clients. In terms of performance our system compares favorably with simpler publish/subscribe schemes that support only equality match. We demonstrate the practical feasibility of SamaritanCloud with an experimental evaluation.