Location-Based Access Control (LBAC) systems support the evaluation of conditions on locations in the enforcement of access control policies. The ability to evaluate conditions on a set of authorized locations has a number of well-known advantages, including enriching access control expressiveness. However, when locations are used in combination with personal identities, users privacy must be considered. In this paper, we describe a solution to integrate a LBAC system with privacy-enhanced techniques based on location obfuscation. Our solution is based on a privacy-aware middleware component that explicitly addresses the trade-off between users privacy and location accuracy by satisfying preferences set by users and maximizing the quality of location information released to LBAC systems.

Recent technological advances have made it feasible to measure and track the location of users, vehicles, and practically any mobile object. Positioning and tracking systems are then collecting a huge amount of potentially sensitive location information, which is a set of data describing a user’s location over a period of time. Since the activities of a user are often related to the locations where such activities are performed, it is natural for users to demand privacy, that is, to require control over the access to their location information. In this chapter, we focus on the privacy aspects of using location information in location-based services (LBSs). LBSs are services that take the current position of the user into consideration when performing their tasks. These services can be accessed from mobile phones, PDA, and any other mobile device. We start the chapter by characterizing the location privacy protection problem and introducing a classification of the main techniques that have been proposed to protect the location privacy. We also survey and discuss recent proposals and ongoing work in the location-based systems area. 1

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Advancements in location technologies reliability and precision are fostering the development of location-based services that make use of the location information of users. An increasingly important category of such services is represented by Location-based Access Control (LBAC) systems that integrate traditional access control mechanisms with access conditions based on the physical position of users and other attributes related to the users location. Since privacy is extremely important for users, protection of their location information is paramount to the success of such emerging location-based services. In this chapter, we first present an overview of Location-based Access Control systems and then characterize the location privacy protection problem. We then discuss the main techniques that have been proposed to protect location information, focusing on the obfuscation-based techniques. We conclude the chapter by showing a privacy-aware LBAC architecture and describing how a location-based access control policy can be evaluated.