A Free Terrain Model for Trajectory K---Anonymity

This paper introduces a privacy model for location based services that utilizes collected movement data to identify parts of the user trajectories, where user privacy is at an elevated risk. To protect the privacy of the user, the proposed methodology transforms the original requests into anonymous counterparts by offering trajectory <em>K</em>---anonymity. As a proof of concept, we build a working prototype that implements our solution approach and is used for experimentation and evaluation purposes. Our implementation relies on a spatial DBMS that carries out part of the necessary analysis. Through experiments we demonstrate the effectiveness of our approach to preserve the <em>K</em>---anonymity of the users for as long as the requested services are in progress.