Patent ID: 7065645

Claim:
A visual authentication system, comprising: a tag attachable to an object, including: an imprinted image displaying a fixed character string in machine-readable symbols; a processor for calculating a response string corresponding to the fixed character string and to a challenge string; a changeable screen controlled by the processor for displaying a changeable image showing the response string in machine-readable symbols; and a disabling means operative to disable said tag upon detecting that said tag is being removed from the object; and an authentication device, including: a scanner for reading from the tag both the imprinted image and the changeable image; an image processor for transforming the imprinted image into a first character string and transforming the changeable image into a readout response string; and an authentication processor for calculating an expected response string corresponding to both the first character string and the challenge string, for comparing the readout response string to the expected response string to obtain a comparison result, and for outputting the comparison result.