8. The method of claim 1 , wherein the document image descriptor comprises an error detecting code or an error correcting code, preferably a Reed-Solomon code.
1. A method, for a first participant in a secure document workflow, of generating workflow information for authenticating a document, the method comprising: receiving an image of the document; generating workflow information for the document image, including a document image descriptor dependent upon the appearance of the document image for later verifying the integrity of a version of the document image that has been printed and scanned, the verification comprising electronically combining or comparing the document image descriptor with said version of the document image; generating a digital signature for later verifying the authenticity of the workflow information, the digital signature being derived from the workflow information using a cryptographic key associated with the first participant; adding the digital signature to the workflow information; and communicating the document image and the workflow information to another workflow participant.