Quantifying Privacy in Cooperative Awareness Services Through Trajectory Reconstruction

Abstract

Cooperatively creating awareness of the vehicle and its surroundings can improve the safety of the transportation system. Creating such awareness involves frequently sharing the vehicle’s location and kinematics information with its surroundings, which can be achieved by broadcasting Cooperative Awareness Messages (CAMs) or Basic Safety Messages (BSMs). The receivers of these messages know the current location and kinematics of the sender and can estimate the possibility of collision. However, continuously receiving CAMs/BSMs allows the receiver to reconstruct the sender’s trajectory, in which the full trajectory may reveal information about the users, such as, house and workplace location. Hence, the user’s privacy is violated. Prior works focused only on location-based trajectory reconstruction and ignored the other kinematics, such as heading and speed. Ignoring such information could lead to underestimating the adversary who seeks to misuse the communication. This work analyses the privacy loss which arises from additional information in BSMs/CAMs. We propose a trajectory reconstruction model that leverages all kinematics (AKs), including location, heading, and speed. The trajectory reconstruction model is composed of two sub-models, namely, inference and data association models. The first sub-model estimates the probability from the estimated value of a vehicle’s kinematics, and the second sub-model performs linking between pseudonyms. We quantify the privacy loss regarding the precision, recall, and F1-score of the ability to identify the correct link between pseudonyms with AKsbased trajectory reconstruction and compare the proposed model with the location-based approach. We also quantify the users’ privacy through the uncertainty in the trajectory reconstruction process. We show that, in some scenarios, the AKs-based trajectory reconstruction gains higher precision, recall, F1-score, and certainty in trajectory reconstruction compared to the locationbased approach.