Revisiting two-hop distance-bounding protocols: Are you really close enough?

Paper i proceeding, 2018

The emergence of ubiquitous computing has led to multiple heterogeneous devices with increased connectivity. In this communication paradigm everything is inter-connected and proximity-based authentication is an indispensable requirement in multiple applications including contactless payments and access control to restricted services/places. Distance-bounding (DB) protocols is the main approach employed to achieve accurate proximity-based authentication. Traditional distance-bounding requires that the prover and the verifier are in each other’s communication range. Recently, Pagnin et al. have proposed a two-hop DB protocol that allows proximity-based authentication, when the prover and the verifier need to rely on an intermediate untrusted party (linker). In this paper, we investigate further the topic of two-hop distance-bounding. We analyse the security of the Pagnin et al. protocol for internal adversaries and we investigate the impact of the position of the linker in the distance-bounding process. We propose a new two-hop DB protocol that is more lightweight and avoids the identified problems. Finally, we extend the protocol to the multi-hop setting and we provide a detailed security analysis for internal adversaries.