A Lightweight Protocol for Validating Proximity in UHF RFID Systems

We present a novel scheme for testing the proximity of an Ultra-high frequency (UHF) Radio Frequency Identification (RFID) transponder, based on the fact that two co-located devices experience correlated channel fluctuations on a reference signal. When the interrogator requests data from the transponder, the latter performs backscattering modulation on the carrier-wave provided by a helper node. The interrogator applies signal processing techniques on the backscattered signal to extract the channel characteristics of the channel between itself and the helper, and the channel between the transponder and the helper. If the two channels are correlated, then the proximity of the transponder is validated by the fundamental properties of spatial channel correlation. The proposed scheme can be employed seamlessly in RFID systems from the transponder's point of view and is resilient to distance-fraud attack.