Patent ID: 7904718

Claim:
A method for differentiating between a first personal digital key (PDK) and a second PDK within a proximity zone of an external device, comprising: using a computer to execute method steps, the steps comprising: obtaining a first differentiation metric associated with the first PDK after it enters the proximity zone, wherein the first differentiation metric is based on a distance metric that measures a distance greater than zero from the PDK to the external device or a detection duration metric that measures a time duration greater than zero once the PDK enters the proximity zone; obtaining a second differentiation metric associated with the second PDK after it enters the proximity zone while the first PDK is present in the proximity zone, wherein the second differentiation metric is based on the distance metric or the detection duration metric; comparing the first differentiation metric to the second differentiation metric; determining that the first PDK is associated with a transaction based on the comparison of the first differentiation metric and the second differentiation metric; responsive to determining that the first PDK is associated with the transaction, executing an authentication test for the first PDK; and authorizing the transaction responsive to the first PDK satisfying the authentication test.