Fighting Fraud With Light

The Naked Scientists spoke to Professor Russell Cowburn, Imperial College London
02 October 2005

Interview with 

Professor Russell Cowburn, Imperial College London


Chris - So you think you've found a way to combat fraud?

Russell - Yes we think so. We're all familiar with the concept of people having individual fingerprints. What we've found is that every bank note, passport, every credit card and virtually every item in the world has it's own secret fingerprint. Now we don't have to put those fingerprints there because they are naturally occurring, but they can be used to identify virtually anything you like.

Chris - How do you do that?

Russell - Well that's the trick. These fingerprints were out there all this time but nobody knew they were there. In my lab one day, we had an accident. We were firing a laser beam at a microchip, nothing to do with security, and the chip fell off. There was a piece of paper where the chip was supposed to be, and we found that when the light bounced off the paper, instead of not carrying any information at all, the laser light was carrying lots and lots of information. Essentially, the laser was interacting with all of the tiny little defects that you get on any surface of paper, plastic or whatever. By looking at those, you can think of them as some kind of fingerprint for that particular item.

Chris - Now we know that a fingerprint is fairly specific to an individual. How likely is it that two bits of paper have the same fingerprint?

Russell - The chance that two bits of paper have the same fingerprint is one in a billion billion billion billion billion billion billion billion billion!

Chris - So a lot!

Russell - Yes, so you can look but I suspect you won't find one!

Chris - That's amazing. So it means that with bank notes, you don't need to put a figure on it any more. You can just scan them as soon as they roll off the presses, lock away its fingerprint and you'd know straight away if it was a forgery.

Russell - That's exactly right, and that's exactly what we're trying to do at the moment. We're talking with some central banks about doing that.

Chris - You must be a millionaire now!

Russell - Er, no. We're very excited because we stumbled across something that we weren't even looking for. We were doing science in a different area, in nanotechnology, and it was only because that chip fell off that we saw that something was unusual and we asked a question.

Chris - Is it just paper that this works on, or does it work on other surfaces like plastic credit cards?

Russell - It works on pretty much everything. The rule of thumb is that if you hold it up and you can see your face in it, then it won't work. Unless it's a perfect mirror or a completely transparent bit of glass, then it has a fingerprint. We can read that fingerprint just by shining a laser beam onto it.

Chris - If I knew the fingerprint that went with a piece of paper, how easy would it be to make another piece of paper with the same fingerprints?

Russell - We don't know how to do that, and we think that that's what makes the technology really secure. Most of the ways of securing things like putting on barcodes and holograms, people know how to do. It doesn't take very long for criminals to work out how to copy that. The beauty of our method is that nobody, not even ourselves, knows how to reproduce the fingerprints. This means that if I turn criminal, I am as unable as anyone else at cracking the system.


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