Preserving Privacy for Location-Based Services with Continuous Queries

Location-based service (LBS) is gaining momentum as GPS-equipped mobile devices become increasingly affordable and popular. One of the potential obstacles faced by LBS is that users may raise concerns about their personal privacy when location data are sent to a distrusted LBS provider. A well-known solution is to render the location data less accurate through spatial or temporal cloaking. In this paper, we show that by combining consecutive location data including speed, heading direction, and cloaked locations, an adversary can obtain more accurate estimation of the actual location. We propose a solution to prevent such inferences by cloaking speed and direction. Since the cloaking is based on estimated future locations, we devise methods for tolerating errors caused by the estimation process. We report simulation results on the tradeoff between the capability of tolerating errors and the degree of cloaking.