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

在这个项目中，我们研究了在不可信的位置服务器基础设施中对用户的私有位置信息进行安全管理的概念和算法。为此，我们在第一个资助期提出了位置共享的概念，通过混淆用户在移动设备上的位置，并将所谓的有限精度的位置共享分配给不同提供商的一组独立服务器，从而保护用户的私人位置信息。该概念有效地保护私有位置信息免受恶意或泄露的位置服务器的攻击，并确保隐私与存储位置共享的泄露位置服务器的数量相匹配。在第二个资助期，我们将项目的范围从单纯的位置信息扩展到语义位置信息，也就是说，我们还考虑地理位置坐标（如餐馆或教堂）所代表的地点类型。为此，我们研究并设计了新的算法，用于对拥有用户位置访问历史的攻击者进行个人语义位置访问的混淆。此外，我们还扩展了这些算法，使其能够与不受信任的位置服务器基础设施一起工作，这样每个位置服务器就存储了关于用户的严格有限的位置历史信息。通过这种方式，我们的算法确保攻击者无法利用历史语义位置信息从混淆的位置数据中重新创建实际位置数据。

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.