Eliminating paper forgeries
There is therefore a great need for a system of authenticating paper documents and detecting alterations after issue. This was the goal of the EU funded 'Secure imprint generated for paper documents' (SIGNED) project. Starting in December 2010, the intiiative ran for 24 months, uniting 5 European partners. The project aimed to provide reliable security information imprinted on the document itself. The project required guaranteed integrity, where a user could detect alteration of a document after production. Other requirements were guaranteed authenticity, where the receiver of a document would reliably know its issuer, and non-repudiation, where the document issuer would be unable to deny production of the signed document. Additional requirements included detection of alterations with high reliability, while ignoring legitimate distortions introduced by printing or scanning. Furthermore, the system had to be applicable to any document, while also being compatible with standard office equipment including faxes. Achieving this was essentially a software task, broken down into 11 achievements against 5 main technical objectives. Fundamental to the system is a robust hashing function, called higher density discrete wavelet transform (HDWT), designed for the project. HDWT means dense square dot patterns printed in the corners and margins of the document, encoding all original content, including text and graphics. The scanned document is analysed by the SIGNED web-based software, which compares the page against the encoded information, quickly highlighting alterations. A secondary function enables creation and insertion of the HDWT codes into documents, using standard open-source barcode software. The SIGNED team also successfully tested the prototype system using common printer and scanner brands. The prototype achieved target values for probability of missed detection and false alarms, meaning that the system reliably detects genuine alterations without yielding false positives. SIGNED's impact will be significant, illustrated by the considerable interest the prototype demonstration received at the IEEE Workshop on Information Forensics and Security in 2012. SIGNED technologies will be applicable to virtually every organisation needing to secure paper documents.
