Differentially private location protection with continuous time stamps for VANETs

Vehicular Ad hoc Networks (VANETs) have higher requirements of continuous Location-Based Services (LBSs). However, the untrusted server could reveal the users’ location privacy in the meantime. Syntactic-based privacy models have been widely used in most of the existing location privacy protection schemes. Whereas, they are suffering from background knowledge attacks, neither do they take the continuous time stamps into account. Therefore we propose a new differential privacy definition in the context of location protection for the VANETs, and we designed an obfuscation mechanism so that fine-grained locations and trajectories will not exposed when vehicles request location-based services on continuous time stamps. Then, we apply the exponential mechanism in the pseudonym permutations to provide disparate pseudonyms for different vehicles when making requests on different time stamps, these pseudonyms can hide the position correlation of vehicles on consecutive time stamps besides releasing them in a coarse-grained form simultaneously. The experimental results on real-world datasets indicate that our scheme significantly outperforms the baseline approaches in data utility.