EPcloak: An Efficient and Privacy-Preserving Spatial Cloaking Scheme for LBSs

Location-Based Services (LBSs) have become one of the most popular activities and affected our daily life a lot. Mobile users can enjoy kinds of conveniences by submitting their location and interest-related queries to the LBS server. However, since these queries may expose sensitive information to the untrusted LBS server, privacy concerns arise. To address the serious privacy issues, we propose a novel collaborative scheme, EPcloak, which combines a privacy-preserving spatial cloaking algorithm and caching to protect user´s privacy. Different from existing schemes, users in EPcloak cache their past service data for future use. When LBSs are needed, a user first uses a Local Searching Algorithm (LSA) to look for service data from the nearby friends of a collaborative group through Ad Hoc networks. If the requirements cannot be satisfied, the user uses a Spatial Cloaking Algorithm (SCA) to forward the query to another user at a certain distance away through a set of forwarders. That user will query the LBS server to get service data for a larger area that can cover the original user´s query area, and send the data back to the original user. SCA protects both user´s location privacy and query privacy. Evaluation results indicate that our proposed LSA and SCA are effective and efficient.