Chord: Thwarting Relay Attacks Among Near Field Communications.

Near field communication (NFC) is an emerging and promising technology envisioned to support a large gamut of applications such as payment and ticketing applications. Unfortunately, there emerges a variety of vulnerabilities that could leave an unwitting user vulnerable to attacks along with the increase of NFC applications. One such potential devastating attack is relay attack, in which adversaries establish a transparently transferring channel between two distant NFC-enabled devices, thus break the assumption that NFC can only work within a rather near distance. In this paper, we propose Chord, an effective method for detecting relay attack. Via measuring the strength of received signal, i.e, the Received Signal Strength Indication (RSSI) during a time span, the two devices are expected to get the same “trace” of RSSI’s variation because of physical proximity. Therefore, the relay attack can be revealed if the peers get a different “trace” from each other, which implies that they do not communicate directly via NFC link. The results of our implementation show that our proposal works as intended, and exhibits an improvement of security with reasonable performance impact.