Enhancing Location Privacy in Wireless LAN Through Disposable Interface Identifiers: A Quantitative Analysis

The recent proliferation of wireless local area networks (WLAN) has introduced new location privacy risks. An adversary controlling several access points could triangulate a client’s position. In addition, interface identifiers uniquely identify each client, allowing tracking of location over time. We enhance location privacy through frequent disposal of a client’s interface identifier. While not preventing triangulation per se, it protects against an adversary following a user’s movements over time. Design challenges include selecting new interface identifiers, detecting address collisions at the MAC layer, and timing identifier switches to balance network disruptions against privacy protection. Using a modified authentication protocol, network operators can still control access to their network. An analysis of a public WLAN usage trace shows that disposing addresses before reassociation already yields significant privacy improvements. Marco Gruteser is a Ph.D. candidate in computer science, advised by Prof. Dirk Grunwald at the University of Colorado at Boulder. His research interests include location privacy, context-aware applications, and wireless networks. He received his MS in computer science from the University of Colorado at Boulder and completed a Vordiplom at the Technical University Darmstadt, Germany. During a one-year leave at the IBM T.J. Watson Research Center, he developed software infrastructure that integrates sensors to support context-aware applications in the BlueSpace smart office project. He is a student member of the ACM. Contact him at Campus Box 430, Boulder, CO 80309-0430;. Dirk Grunwald received his Ph.D. from the University of Illinois in 1989 and joined the University of Colorado the same year. His work addresses research and teaching in the broad area of “computer systems”, which includes computer architecture, operating systems, networks, and storage systems. His interests also include issues in pervasive computing, novel computing models, and enjoying the mountains. He is currently an Associate Professor in the Department of Computer Science and in Electrical and Computer Engineering and is also the Director of the Colorado Center for Information Storage.This revised version was published online in AUgust 2005 with a corrected cover date.