Secure Management of Position Information in Non-trusted Location Server Infrastructures

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In this project, we investigate concepts and algorithms for the secure management of private location information of users in non-trusted location server infrastructures. To this end, we have proposed the concept of position sharing in the first funding period, which protects private location information of users by obfuscating user positions on the mobile device and distributing so-called position shares of limited precision among a set of independent servers of different providers. This concepts effectively protects private location information against malicious or compromised location servers, and ensures the graceful degradation of privacy with the number of compromised location servers storing position shares.In the second funding period we extend the scope of the project from mere location information to semantic location information i.e., we also consider the type of places represented by the geo-location coordinates such as restaurants or churches. To this end, we investigate and design novel algorithms for the obfuscation of individual semantic location visits against attackers who possess histories of location visits of the users. Moreover, we also extend these algorithms to work with non-trusted location server infrastructures such that each location server stores a strictly bounded amount of location history information about the users. In this way, our algorithms ensure that actual location data cannot be recreated from obfuscated location data by attackers exploiting historic semantic location information.