Patent ID: 7302576

Claim:
A method for authenticating a document, comprising: inputting the document and generating document data; determining at least one representation from the document data, the at least one representation comprising information derived from only a portion of the document; determining assist information based on the at least one representation and the document data, the assist information usable to recover the at least one representation from the document data, the assist information usable to recover the at least one representation from a copy of the document containing noise; the assist information only enabling recovery of at least one alternate representation from a copy of the document in which the information has been altered, the at least one representation and the at least one alternate representation being different from one another; generating at least one one-way hash of at least one of the at least one representation of the document data; and appending authentication information to the document, the authentication information comprising the assist information and the at least one one-way hash.