Anonymous Usage of Location-Based Services Through Spatial and Temporal Cloaking Marco Gruteser and Dirk Grunwald Department of Computer Science University of Colorado at Boulder Boulder, CO 80309 fgruteser,grunwaldg@cs.colorado.edu Abstract Advances in sensing and tracking technology enable location-based applications but they also create significant privacy risks. Anonymity can provide a high degree of privacy, save service users from dealing with service providers’ privacy policies, and reduce the service providers’ requirements for safeguarding private information. However, guaranteeing anonymous usage of location-based services requires that the precise location information transmitted by a user cannot be easily used to re-identify the subject. This paper presents a middleware architecture and algorithms that can be used by a centralized location broker service. The adaptive algorithms adjust the resolution of location information along spatial or temporal dimensions to meet specified anonymity constraints based on the entities who may be using location services within a given area. Using a model based on automotive traffic counts and cartographic material, we estimate the realistically expected spatial resolution for different anonymity constraints. The median resolution generated by our algorithms is 125 meters. Thus, anonymous location-based requests for urban areas would have the same accuracy currently needed for E-911 services; this would provide sufficient resolution for wayfinding, automated bus routing services and similar location-dependent services. 1 Introduction Improvements in sensor and wireless communication technology enable accurate, automated determination and dissemination of a user’s or object’s position [1, 2]. There is an immense interest in exploiting this positional data through location-based services (LBS) [3, 4, 5, 6]. For instance, LBSs could tailor their functionality to the user’s current location, or vehicle movement data would…