Paper 'fingerprints' can prevent forgery of documents

Scientists have found an inexpensive way to 'fingerprint' paper documents and verify their authenticity using an off-the-shelf camera, a finding that may help reduce the risk of forgery.

Just by taking a picture of a paper document and analysing the translucent patterns revealed when a light shines through paper, researchers have been able to identify a unique 'texture' fingerprint for every single sheet of paper.

Capturing the random interweaving of the paper particles, scientists from Newcastle University in the UK showed that a unique fingerprint code can be captured and verified with 100 per cent accuracy using nothing more than an off-the-shelf camera.

They further show that the fingerprinting process remains highly reliable even if the paper is treated with rough handling such as crumpling, soaking, scribbling and heating.

"What we have shown is that every piece of paper contains unique intrinsic features just as every person has unique intrinsic biometric features," said Feng Hao, from Newcastle University.

"By using an ordinary light source and an off-the-shelf camera, it takes just 1.3 seconds and one snapshot to capture those features and produce a texture 'fingerprint' that is unique to that document," said Hao, co-author of the study published in the journal ACM Transactions on Information and System Security.

"Cloning the paper document would require reproducing the same random interweaving of the wooden particles in the paper - which is impossible, massively reducing the possibility of forgery," said Hao.

Designing secure documents that provide high levels of security against forgery is a long-standing problem. Even in today's digital age, this problem remains important as paper is still the most common form of proving authenticity - such as receipts, contracts, certificates and passports. While on the surface a sheet of paper may seem like any other sheet, manufacturing paper is a complex process and each sheet is unique.

"Typically, wooden particles are used as the base and multiple substances are used to stick these particles together," said Ehsan Toreini, a PhD student at Newcastle.

"Our idea was that the majority of paper used for official and legal documents, certificates, invoices and so on is not completely opaque," said Toreini. "Different types let through different levels of light and reflect it in different ways and as a result, each one reveals a unique fingerprint. "We proposed an algorithm that generates a compact and unique identifier for each sheet of paper. This identifier is then converted into a QR code which can be verified efficiently off-line by anyone," he said.

"Since this identifier is basically representative of that paper texture, any illegal modifications - including copying the contents of the document to another paper sheet - could be identified," he added.

This technique can be applied to prevent counterfeiting of any physical document that is made of paper material, for example, e-passports and bank notes. One potential application is to verify the authenticity of a university degree certificate.