Abstract: Aiming at the vulnerability to continuous query attacks in the methods based on k-anonymity and difficultly in constructing anonymous region when the number of users is few, a method for trajectory privacy protection based on district partitioning was proposed. A user-group that has the history query points of a particular district was obtained by using a third-party auxiliary server, and the historical query points were downloaded from the users in the user-group by P2P protocol. Then the query result was searched in the historical query information to improve the query efficiency. In addition, a pseudo query point was sent to confuse attackers, and the multiple query points were hidden in the same sub-district by district partitioning to keep the attackers from reconstructing real trajectory of the user to ensure security. The experimental results show that the proposed method can improve the security of user trajectory privacy with the increases of distance and cache time. Compared to the Collaborative Trajectory Privacy Preserving (CTPP) method, when the number of users is 1500, the security is averagely increased about 50% and the query efficiency is averagely improved about 35% (the number of sub-districts is 400).

Key words: trajectory privacy protection, district partitioning, pseudo query point, continuous query

摘要： 针对现有k匿名方法易受连续查询攻击以及在用户数稀少时难以构建匿名区域问题，提出一种基于区域划分的轨迹隐私保护方法。查询用户利用第三方辅助服务器获得拥有特定区域历史查询点的用户组，并通过P2P协议获得用户组中用户的历史查询点，从中搜索所需的查询结果，以提高查询效率。另外，该方法通过发送伪查询点迷惑攻击者，以及利用覆盖用户真实轨迹的区域划分方法，将多个查询点隐藏在同一子区域中，使攻击者无法重构用户的真实轨迹，以保证安全性。实验结果表明，所提方法随着偏离距离和缓存时间的增大，用户轨迹隐私的安全性会提高。在用户数为1500时，与协作轨迹隐私保护（CTPP）方法相比，安全性平均提高约50%，查询效率平均提高约35%（子区域数为400）。

关键词: 轨迹隐私保护, 区域划分, 伪查询点, 连续查询