Over the past decade, smartphones have become the point of convergence for many applications and services. There is a growing trend in which traditional smart-card based services like banking, transport and access control are being provisioned through smartphones. Smartphones with Near Field Communication (NFC) capability can emulate a contactless smart card; popular examples of such services include Google Pay and Apple Pay. Similar to contactless smart cards, NFC-based smartphone transactions are susceptible to relay attacks. For contactless smart cards, distance-bounding protocols are proposed to counter such attacks; for NFC-based smartphone transactions, ambient sensors have been proposed as potential countermeasures. In this study, we have empirically evaluated the suitability of ambient sensors as a proximity detection mechanism for contactless transactions. To provide a comprehensive analysis, we also collected relay attack data to ascertain whether ambient sensors are able to thwart such attacks effectively. We initially evaluated 17 sensors before selecting 7 sensors for in-depth analysis based on their effectiveness as potential proximity detection mechanisms within the constraints of a contactless transaction scenario. Each sensor was used to record 1000 legitimate and relay (illegitimate) contactless transactions at four different physical locations. The analysis of these transactions provides an empirical foundation on which to determine whether ambient sensors provide a strong proximity detection mechanism for security-sensitive applications like banking, transport and high-security access control.
@cite_15: Unless specifically designed for its prevention, none of the existing RFID authentication protocols are immune to relay attacks. Relay attacks generally involve the presence of one or more adversaries who transfer unmodified messages between a prover and a verifier. Given that the message content is not modified, it is rather difficult to address relay attacks through cryptographic means. Extant attempts to prevent relay attacks involve measuring signal strength, round-trip distance, and ambient conditions in the vicinity of prover and verifier. While a majority of related authentication protocols are based on measuring the round-trip distance between prover and verifier using several single-bit challenge-response pairs, recent discussions include physical proximity verification using ambient conditions to address relay attacks. We provide an overview of existing literature on addressing relay attacks through ambient condition measurements. We then propose an elliptic curve-based mutual authentication protocol that addresses relay attacks based on (a) the surface temperature of the prover as measured by prover and verifier and (b) measured single-bit round-trip times between prover and verifier. We also evaluate the security properties of the proposed authentication protocol.
@cite_15 used ambient temperature with an elliptic curve-based RFID and or NFC authentication protocol to determine whether two devices were co-located. Using this method, they were successful in establishing a secure channel; the proposal combines the timing channels in RFID, traditionally used in distance bounding protocols, in conjunction with ambient temperature. Their proposal, however, was not implemented and so there is no experimental data provided to evaluate its efficacy.