Document authentication

A method, system, computer program and web service for authenticating a document is described comprising; receiving a request to verify the earliest date of a document, such a request including the document itself; creating a signature of the received document by running the document against a checksum algorithm; searching a database for a matching signature to the created signature; and responding to the request with a date associated with a matched signature. The checksum algorithm is an MD5 algorithm and will produce a unique signature for each non-identical set of binary data and no two sets of binary data will render an identical signature. Signatures are created of the objects of a document. Separate signatures are created of the content and the formatting of the document.