Traditional methods for localization in wireless networks rely on the correlation of the received signal strength with physical distance. It is also well known, that these mechanisms fail in an adversarial setting due to the lack of robustness of the signal strength property to malicious intent. In this paper, we present a property of the wireless medium, which we call 'wireless congruity', that captures the relative similarities in wireless media characteristics (such as packet receptions, idle channel time, etc.) as observed by two receivers that are in physical proximity of each other. We show that wireless congruity holds promise for secure localization by presenting an initial yet encouraging set of results obtained through extensive experimentation in a rich indoor wireless environment.
I. INTRODUCTIONWith the growth of m-Commerce applications, systems that provide location information for a mobile user are becoming popular. Such localization systems can be classified into two: the ones that use dedicated hardware for localization, such as Cricket [1] which uses ultrasound, and the ones that operate through off-the-shelf 802.11 hardware. The systems in the latter category are of particular commercial interest due to their ease of deployment over the widely available 802.11 WLANs and the resultant cost-savings. Thus, a lot of prior research has focused on building accurate indoor localization systems [2], [3], [4] which use the signal strength property of wireless transmissions to assist in location inference. While signal strength is a good indicator of physical distance, its predictability has become an Achilles heel when faced with the issue of validating it in the presence of malicious intent -it is possible for an attacker to 'guess' the signal strength at a location without being there physically.