Patent ID: 7516325

Claim:
A method of establishing a key between a first device and a second device under control of a common user, said method comprising the steps of: establishing a shared secret in said first device and in said second device; calculating an antispoof variable based at least in part upon said shared secret in said first device and in said second device, said antispoof variable being represented by a plurality of groups of at least one digit; indicating one at a time in sequence, successive ones of said groups of said digits of said antispoof variable from said first device to said common user using a first stimulus; indicating one at a time in sequence, successive ones of said groups of said digits of said antispoof variable from said second device to said common user using a second stimulus in the same order as indicated by said first stimulus; upon said common user verifying that said digits of said antispoof variable from said first device and said second device are the same, completing mutual authentication of said first device and said second device and establishing said key in said first and second devices using said shared secret; wherein the timing of said indicating one at a time in sequence on said first device is time synchronized with the timing of said indicating one at a time in sequence on said second device.