Patent ID: 8886939

Claim:
A method for a first communication device to control access to data by a second communication device, the method comprising: generating a first round trip time signal according to a first secret and according to first round trip time signal generation rules; receiving a certificate of the second device; determining whether the second device is authorized to access the data depending on whether the certificate identifies the second device and on whether the second device is compliant with a set of compliance rules; transmitting a second secret to the second device when the second device is determined to be authorized, the second secret being at least related to the first secret; transmitting a second round trip time signal to the second device at a first time t1; receiving a third round trip time signal, from the second device at the first device, at a second time t2 which is later than the first time t1; the first device determining whether the second device is authorized to access the data by comparing at least a portion of the first round trip time signal with at least a portion of the third round trip time signal to determine whether the first and third round trip time signals meet a relationship criteria, wherein meeting of the relationship criteria indicates that the first secret used by the first device to generate the first round trip time signal is at least related to a third secret used by the second device to generate the third round trip time signal, and indicates that the first round trip time signal generation rules of the first device are at least related to the third round trip time signal generation rules of the second device; determining a round trip time between the first and the second devices depending on a time difference between t1 and t2, determining whether the round trip time is less than a predetermined round trip time threshold; and allowing the second device to access the data when the first and third round trip time signals meet the relationship criteria and the round trip time is determined to be less than the predetermined round trip time threshold.