中文摘要：

集中式可信第三方结构是基于位置的服务中常用的隐私保护结构。然而，一旦中心第三方服务器被攻破或不可信任，用户的位置隐私就有被泄露的风险。针对以上问题，提出一种用户自定义网格化的位置隐私保护方案，先将查询范围自动网格化处理，再结合保序加密技术，使用户的实时位置在隐藏状态下仍能进行比较。由于该方案在整个查询过程中，信息全程处于加密状态，服务器不知道任何用户的具体位置信息，增强了对用户位置隐私的保护；又由于该方案的中心第三方服务器只需要进行简单的比较操作，有效减少了它在处理大量数据时的时间开销。安全分析阐明了该方案的安全性，模拟实验结果表明该方案能够使中心服务器的时间开销明显降低。

英文摘要：

The centralized structure of the trusted third party is a major privacy protection structure on location based services.However,if the central third party server can not be trusted or compromised,users have the risk of leakage of privacy location.Aiming at the above problems,location privacy protection approach based on a user-defined grid to hide location was proposed.The system first automatically converted the query area into a user-defined grid,and then the approach utilized order preserving encryption,which made the user’s real-time position in the hidden state could still be compared.Because the information in the process of the approach was in a state of encryption,the server could not know the user’s location information,thus improved privacy protection of the user location.The central third party server only need to do simple comparison work,so its processing time overhead would effectively decrease.Security analysis certificate the security of the proposed approach and simulation experimental show the proposed approach can reduce the time cost of the central third party server.