Item authentication

An authentication system for and method of authenticating items, the system 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.