Low-power Distance Bounding

Aanjhan Ranganathan, Boris Danev, Srdjan Capkun

A distance bounding system guarantees an upper bound on the physical distance between a verifier and a prover. However, in contrast to a conventional wireless communication system, distance bounding systems introduce tight requirements on the processing delay at the prover and require high distance measurement precision making their practical realization challenging. Prior proposals of distance bounding systems focused primarily on building provers with minimal processing delays but did not consider the power limitations of provers and verifiers. However, in a wide range of applications (e.g., physical access control), provers are expected to be fully or semi-passive introducing additional constraints on the design and implementation of distance bounding systems. In this work, we propose a new physical layer scheme for distance bounding and leverage this scheme to implement a distance bounding system with a low-power prover. Our physical layer combines frequency modulated continuous wave (FMCW) and backscatter communication. The use of backscatter communication enables low power consumption at the prover which is critical for a number of distance bounding applications. By using the FMCW-based physical layer, we further decouple the physical distance estimation from the processing delay at the prover, thereby enabling the realization of the majority of distance bounding protocols developed in prior art. We evaluate our system under various attack scenarios and show that it offers strong security guarantees against distance, mafia and terrorist frauds. Additionally, we validate the communication and distance measurement characteristics of our system through simulations and experiments and show that it is well suited for short-range physical access control and payment applications.

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