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

在本项目中，我们研究了非可信位置服务器基础设施中用户私有位置信息的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，通过混淆移动设备上的用户位置，并在不同提供商的一组独立服务器之间分发所谓的有限精度的位置份额，来保护用户的私人位置信息。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，即我们还考虑了由地理位置坐标表示的地点的类型，如餐馆或教堂。为此，我们研究并设计了新的算法来混淆个体语义位置访问，以对抗拥有用户位置访问历史的攻击者。此外，我们还将这些算法扩展到与非可信位置服务器基础设施一起工作，使得每个位置服务器存储关于用户的严格有限量的位置历史信息。通过这种方式，我们的算法确保了攻击者不能利用历史语义位置信息从混淆的位置数据中重建实际的位置数据。

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.