中文摘要：

随着云服务与位置感知设备的普及,大量与位置相关的信息需要外包给服务提供商,由此引发的空间数据隐私问题得到了学术界的广泛关注.Hilbert曲线作为一种空间转换的方法,被广泛应用于空间数据的隐私保护中,但标准Hilbert曲线未考虑兴趣点的分布特征,可能需要多次调整曲线参数,且无法支持数据拥有者对空间区域的自定义授权.针对上述问题,提出一种可以根据兴趣点分布而自适应变化的Hilbert曲线（AHC）,该曲线根据设定的存储容量将空间划分为原子区域,使用Hilbert曲线的分形规则确定各原子区域的顺序,并由此生成密钥树,数据拥有者可以将密钥树的一部分共享给授权使用者,从而实现对空间区域的自定义授权;设计了基于AHC的空间查询处理方案,支持兴趣点的索引值计算、范围查询与KNN查询处理;定义了空洞指数以量化外包数据的隐私信息泄露风险.在真实数据集与模拟数据集上的实验表明,与标准Hilbert曲线相比,该文提出的AHC在进行空间转换方面具有更高的安全性与更优的查询效率.

英文摘要：

With the popularity of cloud computing services and location-aware devices,a large amount of information related to location needs to be outsourced to the service provider,so the research about privacy protection for spatial data gets increasing attention from academia.As a kind of spatial transformation approach,Hilbert curve is widely used in privacy protection for spatial data.However,the standard Hilbert curve does not take the distribution of the points of interest （POI） into consideration,so the curve parameters may need to be adjusted several times.Moreover,it cannot support custom authorization of the space for the data owner.To solve these problems,in this paper,first,we propose the adaptive Hilbert curve （AHC）,which dynamically adapts to the POI distribution.AHC partitions the space into atom regions according to the setting capacity,and then determines the order of atom region based on the Hilbert curve fractal rule.The transformation key tree is constructed based on the atom region order,and the data owner can share part of the key tree with the authorized user,so as to realize the custom authorization of the space.Second,a spatial query processing scheme based on AHC is designed,including the index value calculation algorithm for POI,range and KNN query processing schemes.Third,the null value index is defined to quantify the leakage risk of privacy information.Finally,a series of experiments are conducted using real and synthetic datasets,and the results show that,in the aspect of spatial transformation,AHC is more security and provides higher query efficiency than the standard Hilbert curve.