Patent ID: 8552903

Claim:
A method operational in a first device for verifying a distance, comprising: determining the distance between the first device and a second device; comparing the determined distance to a threshold maximum acceptable distance to determine if the determined distance is equal to or less than the threshold maximum acceptable distance; transmitting, after the determination of the distance and that the determined distance is equal to or less than the threshold maximum acceptable distance, a first set of at least one first signal to the second device, the first set of at least one signal including a random sequence unknown to the second device; receiving a second set of at least one second signal transmitted by the second device in response to the first set of at least one first signal, the second set of at least one second signal generated by applying a function to the random sequence of the first set of at least one first signal; determining, based on an actual round-trip time from transmission of the first set of at least one first signal to reception of the second set of at least one second signal and an expected round-trip time for the previously determined distance, whether the previously determined distance between the first device and the second device is valid or allowable; and causing the second device to take one or more actions, in response to verification of the validity or allowability of the previously determined distance.