Private geosocial networking

Location based social or geosocial networks (GSNs) have recently emerged as a natural combination of location based services with online social networks: users register their location and activities, share it with friends and achieve special status (e.g., "mayorship" badges) based on aggregate location predicates. Boasting millions of users and tens of daily check-ins, such services pose significant privacy threats: user location information may be tracked and leaked to third parties. Conversely, a solution enabling location privacy may provide cheating capabilities to users wanting to claim special location status. In this paper we introduce new mechanisms that allow users to (inter)act privately in today's geosocial networks while simultaneously ensuring honest behaviors. We show that our solutions are efficient both on the provider and the client side.