Patent ID: 8225094

Claim:
A method of establishing a link key between a first device operable to authenticate a second device, the method comprising: the first device permitting non-sensitive communications with the second device when the first and second devices are spaced from each other within a first operating range; the first device permitting sensitive communications with the second device only when the first and second devices are spaced from each other within a second operating range, the second operating range being less than the first operating range; upon detecting initiation of a pairing process for establishing the link key, the first device sending a challenge to the second device to both verify the identity of the second device and determine a distance between the first and second devices; the first device receiving, from the second device, a response to the challenge; the first device determining whether the response is a function of at least a portion of the challenge and information in the second device; the first device using the response to also determine a response time associated with receipt of the response to the challenge; the first device using the response time to determine the distance between the first and second devices; and if the distance between the first and second devices is within the second operating range, and the response is a function of both at least a portion of the challenge and information in the second device, initiating an authentication process to establish the link key in the first device to permit the link key to be used in subsequent communications.