Distance bounding protocols have been proposed for many security critical applications as a means of getting an upper bound on the physical distance to a communication partner. As such, distance bounding protocols are executed frequently, e.g., to keep node locations up to date, etc. We analyze distance bounding protocols in terms of their location privacy and we show that they leak information about the location and distance between communicating partners even to passive attackers. This location and distance information may be highly sensitive since it can form the basis for access control, key establishment, or be used as input to location aware applications. We analyze, in a number of scenarios, how much information distance bounding protocols leak. We further discuss several straightforward countermeasures and show why they do not provide adequate protection against distance leakage. Finally, we propose a location private distance bounding protocol that maintains the properties of existing distance bounding protocols while leaking no information about the distance measured between the communicating parties.
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