A data processing system for distributing and authenticating documents from a plurality of parties to a recipient data processing apparatus is disclosed. The system comprises a plurality of document distribution devices each configured to generate an original hash value from the content of a file containing a document to be distributed. A recipient data processing apparatus is configured to generate an original super hash value from the plurality of the original hash values, and to distribute the original super hash value to each of the document distribution devices. The system provides assurance that distributed documents have not been tampered with during communication, by an unscrupulous distributing party, or by an unscrupulous recipient by only submitting a hash value of the document to be distributed. The hash value provides for assurance at the eventual recipient of the document that no changes to the document have been made.