Preserving User Privacy and Preventing Location Server Content in Location Based Service

Nowadays, it is very easy for a person to learn his/her location with the help of a Global Positioning System (GPS) enabled device. A location-based service (LBS) is a new and developing technology for mobile users. When this location is provided to a LBS via querying, it is possible to learn location dependent information, such as locations of friends or places, weather or traffic conditions around the location. This problem is defined as follows: (i) a user wants to query a database of location data, known as Points Of Interest (POIs), 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.