Privacy-Preserving 802.11 Access-Point Discovery

Abstract

It is usual for 802.11 WLAN clients to probe actively for access points in order to hasten AP discovery and to find "hidden" APs. These probes reveal the client's list of preferred networks, thus, present a privacy risk: an eavesdropper can infer attributes of the client based on its associations with networks. We propose an access-point discovery protocol that supports fast discovery and hidden networks while also preserving privacy. Our solution is incrementally deployable, efficient, requires only small modifications to current client and AP implementations, interoperates with current networks, and does not change the user experience. We note that our solution is faster than the standard hidden-network discovery protocol based on measurements on a prototype implementation.

Publications

• Janne Lindqvist, Tuomas Aura, George Danezis, Teemu Koponen, Annu Myllyniemi, Jussi Mäki and Michael Roe, Privacy-Preserving 802.11 Access-Point Discovery (full version), Microsoft Research Technical Report, MSR-TR-2009-7, January 2009.
• Janne Lindqvist, Tuomas Aura, George Danezis, Teemu Koponen, Annu Myllyniemi, Jussi Mäki and Michael Roe, Privacy-Preserving 802.11 Access-Point Discovery, in Proceedings of Second ACM Conference on Wireless Network Security (WiSec'09), March 16-18, Zürich, Switzerland.

Presentations

University of Cambridge Computer Laboratory Security Seminar Series on February 3, 2009. Slides available.

Compact version in Second ACM Conference on Wireless Network Security (WiSec'09), March 16-18, Zürich, Switzerland. Slides available.

Patches

Installation instructions
madwifi-0.9.4-ppdp.patch
hostapd-0.6.7-ppdp.patch
madwifi-svn-3940-ppdp.patch
wpa_supplicant-0.6.7-ppdp.patch

For questions or comments on this work email janne.lindqvist(a)tml.hut.fi. Please note that we do not actively maintain and support the patches.