A hybrid approach for privacy-preserving processing of knn queries in mobile database systems

Abstract

In mobile object database systems, both query issuers and queried objects are subject to location privacy intrusion. One solution to this problem is to have users reduce their location resolution when making location update. Such location cloaking allows mobile objects to achieve a desired level of protection, but may not produce accurate query results. Alternatively, one can apply cryptography techniques such as secure multiparty computation to compute the spatial relationship among mobile objects without having mobile objects to disclose their location at all. This strategy produces high quality query results, but in general are computation-intensive, especially when a large number of mobile objects are involved. In this paper, we present a hybrid approach that mitigates the above dilemma. Our idea is to compute approximate query results based on cloaked location information and then refine query results by applying homomorphic encryption. We demonstrate that this approach can be used for efficient and privacy-preserving processing of KNN queries and evaluate its performance through simulation.