Research On Location Privacy Protection Technology For Location-based Services In Mobile Computing Environment

With the development of 3G and 4G,the smart phones become popular in the young people. At the same time, the location-based services appear and become popular. When the people enjoy the convenience of location-based services, they have to send their precise location information to the untrusted location service providers. Untrusted location service providers may betray the users’ location information for economic benefits.In order to use location-based services without revealing the precise location information, a lot of scholars proposed many algorithms for location privacy protection. However, these algorithms considered neither the security of the wireless transmission nor the creditworthiness of the centralized anonymizer and the users. The attacker can obtain the users’ location information by many ways. For example, eavesdrops the wireless net, attacks the centralized anonymizer, and originates a P2 P anonymous query.In this thesis, the core contents are how to protect the users’ precise location informations. The quasi-identifier is the users’ precise location informations. Author studied the location privacy protection algorithms based on encryption, not fully trusted third party, and untrusted third party.The mainly contribution of this thesis is the following:1. Proposes a location privacy protection algorithm based on the trusted third party.In order to solve the security problem of the data which were translated by the wireless net, author proposed the location privacy protection algorithm based encryption. It used the combination scheme of symmetric encryption and asymmetric encryption to protect the data. The experiment verified that the combination encryption scheme was suitable for the location privacy protection.2. Proposes a location privacy protection algorithm based on the not fully trusted third party.When the attacker controlled the third party, the precise location information would be exposed. In order to solve this problem, author proposed the twice anonymity location privacy protection algorithm based on the not fully trusted third party. It used the grid areas instead of the users’ exact locations. This was the first anonymous for users to the third party. It generates anonymous spatial region(ASR) using the grid areas as the basic unit to meet the users’ privacy requirements. This was the second anonymous for users to the location service providers. Author proposed the QoS model of the grid area, studied the problems of optimization and randomized for the ASR.3. Proposes a location privacy protection hybrid processing algorithm based on the untrusted users.When the attacker originated a P2 P anonymous query, the precise real-time location informations of the neighboring users would be exposed. In order to solve this problem, author proposed the twice anonymity location privacy protection hybrid processing algorithm. It integrated the P2 P anonymous and the centralized anonymous to solve the problem of insufficient users for classic P2 P anonymous algorithm. It utilized the proxy user as the center to generate the ASR, so the real query user would not be in the center of the ASR. It utilized neighbors’ information download directly from the anonymizer, so the delay of the query would not too long again.4. Proposes a location privacy protection algorithm based on untrusted third party.The twice anonymity location privacy protection algorithm unified the creditworthiness for all the users to the centralized third party, and the query processing efficiency was low for the k-nearest neighbors query. In order to solve these problems, author proposed the incremental KNN inquiry algorithm based on the grid of latitude-longitude for location privacy protection. It let all the users generate ASR using the grids of latitude-longitude as the basic unit to meet their privacy requirements. Users reported the ASR instead of the grid id, so it enabled the personalized creditworthiness. Author introduced the incremental search strategy to solve the low efficiency problem for the k-nearest neighbor query. To achieve a more accurate filtering, author proposed the initial filtering algorithm based on counterclockwise for the centralized anonymous assistant.