The Bank of England has never commented publicly on the existence of the so-called EURion Constellation. No one, from bank officials to equipment manufacturers, wants to talk about it. Getting confirmation of how the pattern works – or even whether it does what researchers think it does – is difficult. Kuhn has not been able to independently verify this theory. Kuhn named the pattern the EURion Constellation after the astronomical constellation of Orion, which it resembles.Īlthough Kuhn thinks colours are one key part of the code, others have suggested that photocopiers are also looking for specific distances between the five circles. “There appears to be some circuitry that requires the circles to be present in a colour channel, not in a black-and-white channel,” he says. But when Kuhn coloured in the circles, the anti-counterfeiting message was churned out instead. When it was a black-and-white pattern, the photocopier reproduced it without quibbling. At first, he drew the pattern in isolation on a blank piece of paper, printed it and tried to photocopy it.
But since different notes varied their colours and orientations of the patterns, even across different denominations of the same currency, how did colour photocopiers pick out the pattern each time? Other currencies around the world, it soon emerged, were printed with the same pattern. So a recurring pattern of five circles existed on sterling and euro banknotes, on both the front and back. The pattern was there, too, but on the front of the note it was hidden in a motif of printed music: the circles were printed as the heads of the musical notes. I stared at it for a while and I saw that the constellation inside this pattern was recurring.” On the 10-euro banknote, I spotted this particularly obvious pattern of little circles. How did the copier know what it was being asked to print? “The euro banknotes had just come out,” says Kuhn, “and I had a 10-euro banknote in my wallet. Instead came a message printed in various languages – explaining that copying banknotes was illegal.
But no colour reproduction of the note appeared in the tray. He closed the lid, pressed the copy button and waited. Kuhn placed a British £20 note on the glass surface to scan. “We went straight for the banknotes.” (Don’t try this at home – the photocopying of banknotes, in the UK and in other countries, is illegal). “We were students,” he recalls with a laugh. It didn’t take him long to decide on the best way to test its abilities. It was the early 2000s, and word of the new-fangled contraption quickly got around – including to computer scientist Markus Kuhn, then a PhD student. A brand-new Xerox colour photocopier had just arrived at one of Cambridge’s industrial labs.