A Terrorist-fraud Resistant and Extractor-free Anonymous Distance-bounding Protocol

Abstract

Distance-bounding protocols have been introduced to thwart relay attacks against contactless authentication protocols. In this context, verifiers have to authenticate the credentials of untrusted provers. Unfortunately, these protocols are themselves subject to complex threats such as terrorist-fraud attacks, in which a malicious prover helps an accomplice to authenticate. Provably guaranteeing the resistance of distance-bounding protocols to these attacks is complex. The classical solutions assume that rational provers want to protect their long-term authentication credentials, even with respect to their accomplices. Thus, terrorist-fraud resistant protocols generally rely on artificial extraction mechanisms, ensuring that an accomplice can retrieve the credential of his partnering prover, if he is able to authenticate. We propose a novel approach to obtain provable terrorist-fraud resistant protocols that does not rely on an accomplice being able to extract any long-term key. Instead, we simply assume that he can replay the information received from the prover. Thus, rational provers should refuse to cooperate with third parties if they can impersonate them freely afterwards. We introduce a generic construction for provably secure distance-bounding protocols, and give three instances of this construction: (1) an efficient symmetric-key protocol, (2) a public-key protocol protecting the identities of provers against external eavesdroppers, and finally (3) a fully anonymous protocol protecting the identities of provers even against malicious verifiers that try to profile them.