Patent ID: 8330601

Claim:
A method of detecting tampering of a physical article, the method comprising the steps of: receiving a first collective response from a first set of tag response signals at a first point in time, the first collective response including a tag response signal from each RF tag of a first set of RF tags associated with the physical article; recording the first collective response as a first response signature for the physical article; receiving a second collective response from a second set of tag response signals at a second point in time, the second collective response including a tag response signal from each RF tag of the first set of RF tags associated with the physical article; comparing the second collective response with the first response signature; determining from the step of comparing whether any of the RF tags have been moved spatially relative to the other RF tags on the physical article; and interpreting a result of the step of determining as an indication that the physical article has been tampered, when the step of determining indicates: that a relative spacing between the RF tags associated with the physical article has changed from the first point in time to the second point in time; or that a relative orientation of the RF tags associated with the physical article has changed from the first point in time to the second point in time.