Evaluating the eavesdropping range of varying magnetic field strengths in NFC standards

Measurements results are presented to evaluate the distance at which a carrier signal of 13.56MHz can be eavesdropped by a “rogue” antenna, which is transmitted by an inductive loop H-antenna, thus representative of a contactless payment device employing near field communication (NFC). Results are evaluated based on the magnetic H-fields used in the ISO14443 standard, while the ability to receive a carrier is based upon the minimum noise floor achievable by a radio receiver at such frequencies and bandwidths. Depending on the size of H-field and the antenna design, measurements indicate that in general the maximum eavesdropping range with practical radio apparatus is largely due to the background noise, which larger antennas were susceptible to in the laboratory environment.