Abstract: A check or other document verification method in which a data encryption algorithm is applied to personal identification number (PIN) and selected other information particular to each document such as check number or amount of check. The resulting derivation is printed on the face of the document at the time the document is originated, in human readable form and possibly in machine readable form. The recipient of the document is issued a proprietary card, preferably an integrated circuit or "smart card", which contains an identical algorithm to that used when the document was originated. When the document holder presents a check for cashing or otherwise presents a document for verification, the cardholder is first identified with the card by inserting the card in a terminal and manually entering a PIN as is a common practice.