n-CD: A geometric approach to preserving location privacy in location-based services

With great advances in mobile devices, e.g., smart phones and tablets, location-based services (LBSs) have recently emerged as a very popular application in mobile networks. However, since LBS service providers require users to report their location information, how to preserve users´ location privacy is one of the most challenging problems in LBSs. Most existing approaches either cannot fully protect users´ location privacy, or cannot provide accurate LBSs. Many of them also need the help of a trusted third-party, which may not always be available. In this paper, we propose a geometric approach, called n-CD, to provide realtime accurate LBSs while preserving users´ location privacy without involving any third-party. Specifically, we first divide a user´s region of interest (ROI), which is a disk centered at the user´s location, into n equal sectors. Then, we generate n concealing disks (CDs), one for each sector, one by one to collaboratively and fully cover each of the n sectors. We call the area covered by the n CDs the concealing space, which fully contains the user´s ROI. After rotating the concealing space with respect to the user´s location, we send the rotated centers of the n CDs along with their radii to the service provider, instead of the user´s real location and his/her ROI. To investigate the performance of n-CD, we theoretically analyze its privacy level and concealing cost. Extensive simulations are finally conducted to evaluate the efficacy and efficiency of the proposed schemes.