Authentication using near field communication with varied signal strength

摘要

A method and system for authenticating a user of a near field communications (NFC) transmitter (such as an identifying tag or card) at an NFC receiver or reader comprises: receiving 404 at the receiver a signal comprising a first unique identifier; measuring 406 the signal strength of this signal and tracking how it varies with time; converting 408 this variation into a second identifier; comparing 410 the first unique identifier with the second identifier to determine whether there is a correlation; authenticating 414 the user if they correlate correctly. The signal strength may be varied by moving the transmitter towards and away from the receiver in a predetermined pattern of movement. The method may be used to determine the outcome of a transaction, and the transaction may be denied or not completed 412 if the identifiers do not correlate. The transmitter may be passive and powered by the NFC reader.