Research On The Techniques Of Location Priavacy Prsesrving On Road Network

With the rapid development of the third generation of mobile communication technology, making it possible to provide location-based services (LBS) containing much information to mobile users’through wireless network. Though LBS bring great convenience for people, it will lead the user’s location privacy to be leaked. That is because the query request that the mobile user sent contained his exact location information. So, it is important to protect the mobile users’location privacy while providing their location-based services.A lot of methods have been proposed to protect the mobile user’s location privacy currently. Most methods supposed that users move in the euclidean space, and transfer the exact location of a user to a spatial area, and make an attacker cannot identify the true position of the user. But in real life, whether pedestrians or vehicles, they usually travel along a fixed road network. Thus, existing methods are not suitable for road network environment. Moreover, because one-way streets play a significant role in alleviating traffic pressure, decreasing intersection conflict and improving the speed of vehicles, many domestic and overseas cities have implemented one-way traffic. For these reasons, this thesis makes an intensive study on the problem of protecting location privacy on simple road network that only contains two-way streets and complex road network that contains both two-way streets and one-way streets.Firstly, according to the structural characteristics of the simple and the complex road networks, this thesis proposes two cloaking subgraph structures, cloaking cycle and cloaking tree. By using the structures of the cloaking cycle and the cloaking tree, blur the location information of a mobile user on road network and make an attacker cannot identify the true position of the user, even the attacker has known the privacy protecting algorithm. Then for the problem of how to construct the subgraph structures of the cloaking cycle and the cloaking tree, this thesis proposes a novel location privacy preserving approach CCF, which finds cycles and forest that satisfy certain conditions using the breadth-first search in undirected graph and directed graph. Moreover, in order to test the performance of CCF, this thesis does kNN query processing for subgraphs and filters the returned candidate results by simulating the location server and the anonymizer respectively. In an experiment test based on the real and simulated datasets, the effectiveness on protecting location privacy and efficiency on providing quality of CCF are given.