Centroid-based KNN query in mobile service of LBS

With the increasing use of GPS-embedded mobile phone in location-based services (LBSs), people's location privacy is facing considerable challenge. Therefore, we propose a centroid- based method of K-nearest neighbor (KNN) query for LBSs. Unlike previous dummy-based approaches, our method sends a request to the LBS server that does not contain the genuine user location, and only requires the server to return the results of the client needs thus to reduce the downstream communication cost. We also propose an effective KNN(k-nearest neighbor) search algorithm to reduce the processing time of the server side . This algorithm can reduce bandwidth usages and efficiently support KNN queries without revealing the private information of the query issuer. Security analysis and empirical evaluation results verify the effectiveness and efficiency of our scheme.