Privacy Preserving Location-Based Service Protocol

Location-based service (LBS) is booming up in recent years with the rapid growth of mobile devices and the emerging of cloud computing paradigm. Along with the challenges to establish LBS and the user privacy issue becomes the most important concern. So successful privacy-preserving LBS must be secure and provide accurate query results. In this paper we present a solution to one of the location-based query problems. This problems are defined as follows: (i) a user wants to query a database of location data, known as Points Of Interest (POI), and does not want to reveal his/her location to the server due to privacy concerns; (ii) the owner of the location data, that is, the location server, does not want to simply distribute its data to all users. The location server needs to have some control over its data, since the data is its asset. For this work, we propose a private circular query protocol (PCQP) to deal with the privacy and the accuracy issues of privacypreserving LBS. The protocol includes space filling curve and a public key homomorphic cryptosystem. As a result, the security level of the proposed protocol is close to perfect secrecy without the help of a trusted third party and simulation results show that the -NN query accuracy rate of the proposed protocol is higher than 90% even when is large.