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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.