Patent ID: 7559466

Claim:
An authentication system for authenticating items, comprising: a processing unit for generating indicia for imprints to be applied to items and authenticating imprints applied to items, each indicium including a cryptographically-encoded component; at least one item printing station for printing imprints on items as generated by the processing unit; and at least one item presentation station to which items are presented in authenticating the same, wherein the at least one item presentation station is configured to transmit data relating to the indicium on an item presented thereto to the processing unit, and receive an authentication message in dependence upon whether the indicium is determined to be valid or invalid, wherein the indicium comprises at least one security parameter which is not provided in human-readable form in the imprint, wherein data relating to a previously-authenticated indicium is stored by the processing unit and, if the transmitted data indicates the indicium is a duplicate of the previously authenticated indicium, the indicium is determined to be invalid.