Privacy aware collaborative traffic monitoring via anonymous access and autonomous location update mechanism

Official URL: http://risc01.sabanciuniv.edu/record=b1479203 (Table of Contents)

Collaborative Traffic Monitoring, CTM, systems collect information from users in the aim of generating a global picture of traffic status. Users send their location information including speed and directions, and in return they get reports about traffic in certain regions. There are two major approaches for the deployment of CTM systems. The first approach relies on dedicated communication infrastructure (DI). This approach is still being investigated by researchers and there is no important deployments done yet. The other approach utilizes existing communication infrastructures (EI) such as Wi-Fi, GSM, and GPRS for communication between users and traffic server. Due to the sensitivity of location information, different privacy preserving techniques have been proposed for both DI and EI approaches. In DI approach the concentration was on anonymous access using pseudonyms. In EI approach privacy techniques concentrate on hiding the identity of a particular user within other k-1 users at the same region or time stamp by using cloaking. Cloaking means generalization of location or time stamp so that other k-1 users will have the same generalized value. Unfortunately, cloaking decreases the quality of the data and requires a Trusted Third Party (TTP) to determine the cloaked region or cloaked time stamp. In this thesis, we propose a Privacy Aware Collaborative Traffic Monitoring System (PA-CTM) that considers the privacy and security properties of VANETs and existing infrastructures. PA-CTM provides a client server architecture that relies on existing infrastructures and enhances privacy by (1) Using a robust Collusion Resistant Pseudonym Providing System, CoRPPS, for anonymous access. Users are able to change their pseudonyms and hence hide their complete trajectory information form traffic server; (2) Utilizing a novel Autonomous Location Update Mechanism, ALUM, that does not rely on a Trusted Third Party and uses only local parameters (speed and direction) for triggering a location update or pseudonym change. Our performance results showed that CoRPPS provides a high level of anonymity with strong resistant against collusion attacks. Performance results also showed that ALUM is effective for traffic monitoring in terms of both privacy and utility.