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RFID to be put out of business by paper "fingerprinting"?

Plans to embed RFID chips in passports, driver licences and other important documents may be abandoned, with the discovery that you can't forge a piece of paper.

According to a research paper published in Nature, the actual paper is the key. So, when it comes to ID cards and credit cards, is the plastic:

"We have found that almost all paper documents, plastic cards and product packaging contain a unique physical identity code formed from microscopic imperfections in the surface," report the Imperial College team - contact Russell P. Cowburn [right].

It is possible to destroy a piece of paper, but not to forge it. And the original piece of paper retains its "fingerprint" even when damaged - severely damaged.

"It can be rapidly read using a low-cost portable laser scanner. Most forms of document and branded-product fraud could be rendered obsolete by use of this code," reports Cowburn.

Stephen Leahy says that the detection process makes use of the optical phenomenon known as laser speckle. Writing in Wired, Leahy reports: "Light coming from a focused laser is coherent, or in phase, but when it strikes a microscopically rough surface like a piece of paper, the light is scattered, producing a pattern of light and dark 'speckles.' The scanner's photodetectors digitise and record this pattern."

The ability to detect a document's unique signature can survive considerable abuse of the paper or plastic. Leahy points out, however, that you can still steal it; the fact that the document is valid, doesn't mean that the bearer acquired it honestly.

It also seems to imply that the stuff written on the document can be deleted and over-written without spoiling the "signature".

According to Optics the really big advantage is the speed with which the signature can be matched; each signature takes less than half a kilobyte of storage; some can be matched against a 200 byte signature.

According to the Boston Globe, Ingenia technology (Cowburn is a director) funded the research.

The drawback would appear to be cost: even if made in large quantities, a suitable field scanner would cost $1,000 to build, possibly ruling this out for routine validation at retail for most smaller shops. This won't stop the excitement generated by the current obsession with airport security and suicide bombers, however - but if you couple this with the news that you will get one "false positive" in a thousand documents, it does suggest that the excitement may be premature.

The obvious advantage is that the actual identity document doesn't have to be expensive to produce. Against that, holograms are pretty cheap, these days...

Full details in the Wired report

History of the project in the Boston Globe

Summary of the signature technology at Optics.org