EXPHLOT: explainable privacy assessment for human location trajectories

Human mobility data play a crucial role in understand- ing mobility patterns and developing analytical services across various domains such as urban planning, transportation, and public health. How- ever, due to the sensitive nature of this data, accurately identifying pri- vacy risks is essential before deciding to release it to the public. Recent work has proposed the use of machine learning models for predicting privacy risk on raw mobility trajectories and the use of shap for risk explanation. However, applying shap to mobility data results in expla- nations that are of limited use both for privacy experts and end-users. In this work, we present a novel version of the Expert privacy risk predic- tion and explanation framework specifically tailored for human mobility data. We leverage state-of-the-art algorithms in time series classification, as Rocket and InceptionTime, to improve risk prediction while reduc- ing computation time. Additionally, we address two key issues with shap explanation on mobility data: first, we devise an entropy-based mask to efficiently compute shap values for privacy risk in mobility data; second, we develop a module for interactive analysis and visualization of shap values over a map, empowering users with an intuitive understanding of shap values and privacy risk.