Hierarchical interpolation point anonymity for trajectory privacy protection

The traditional trajectory privacy protection algorithm approaches the task as a single-layer problem. Taking a perspective in harmony with an approach more characteristic of human thinking, in which complex problems are solved hierarchically, we propose a two-level hierarchical granularity model for this problem. The first level of the proposed model is a coarse-grained layer, in which the original dataset is divided into groups. The second level is a fine-grained layer, where problems are solved in each group instead of on the original dataset, which reduces complexity and computation while improving efficiency. On the basis of this hierarchical model, we propose the interpolation trajectory-anonymous privacy protection algorithm with temporal and spatial granularity constraints. In addition, we propose interpolation-based modified Hausdorff distance on adjacent segment (IMHD_AS), which provides a smaller clustering area and better data utility than the traditional Euclidean distance, as the trajectory similarity criterion for clustering within each group. Further, we theoretically prove that the proposed algorithm outperforms the traditional algorithm in terms of data distortion and anonymity cost and verify its efficacy experimentally. Compared with the classic anonymity algorithm, the maximum information loss and the anonymity cost are reduced by up to 21.04% and 28.32%, respectively.