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The EURion Constellation - DRM for printed materials

Many banknotes- English, Swedish, or Euro; the almighty US dollar, the Singaporean dollar, and the Djiboutian franc all have something in common. They all have a design feature consisting of a pattern of faint yellow or green circles. Five unfilled thick circles, one in the centre and four surrounding it, form a pattern somewhere on the note. The circles are 1mm in diameter. The largest distance from the centre circle to an outlier is about 4mm. The square of the distances form integer ratios.

The EURion constellation looks something like this:


      o    o
         o
            o
     o     
and is repeated, rotated and translated to cover a certain area of the note, on at least one side.

It's worked into the patterns on banknotes in clever ways. On the Swedish 100kr note it appears as random 'bubbles' around Carl von Linné's head. The €5 note has a similar arrangement. Yellow circles form the constellation behind the repeating grey-green hexagon pattern near the arch image. The English £20 note has a musical theme. One side features the stern face of Sir Edward Elgar, Saint Cecilia, and a trumpeting angel with notes and flat-signs. On the other side, level with the Queen's forehead are two lines of a musical score. The notes form a EURion constellation, not a tune. The €10 note has a pattern of circles like snow- but it's EURion again.

This pattern is designed to be discreet if not completely undetectable to the disinterested human eye. But: it's dead easy for machines to spot. Colour photocopiers will not copy banknotes. Paintshop Pro and Adobe Photoshop will not open or scan images containing banknotes. It's thought that they use the EURion Constellation as part of their detection process. Incidentally, this undoubtedly would not prevent dedicated forgers, and it will increase the complexity of the copiers and software. For complexity, read cost, reduced performance and lower utility.

The latest research indicates that there is more to this than just the EURion mark. There is something else that all these banknotes have in common that image software recognises. But the best efforts of part-time steganographers can't yet reveal what it is. For now, the EURion Constellation is the only part of the swirling patterns on banknotes with a publicly known meaning.

It is thought that the system was invented by the OMRON Corporation of Japan, who make electronic ticket checking machines amongst other things. But the origins of the EURion Constellation and the other unknown banknote marks are shrouded in secrecy- no law or published agreement between banks, governments or image-processing suppliers describes it or requires it.

The upshot for us disaffected techo-fiddlers, is that we can add the EURion Constellation to any document. An application called Eurionize will add the image to any postscript file in hard-to-spot yellow-on-white. It will then be protected from being copied in colour; or scanned by the most common commercial image software. This is what DRM schemes promise- a hidden feature of a media file that instructs software or playback devices to restrict playback or copying.

The European Central Bank may have had the EURion Constellation in mind when it called for a consultation "regarding possible legislation on the incorporation of counterfeit deterrence technology in products capable of handling digital images" in the Official Journal dated 24th October 2003. They call for a law that would require such a system to be mandatory in all imaging products. The mark itself has been in use since 1996 at least.

The name "EURion Constellation" was coined by researcher Markus Kuhn, who was the first to describe it. It comes from the "EUR" (the three-letter symbol for the Euro), and the "Orion Constellation" which it closely resembles.

Off the top of my head, then corrected by the following sources:

  • http://slashdot.org/articles/04/01/08/0111228.shtml?tid=152&tid=185
  • http://en.wikipedia.org/wiki/EURion_constellation
  • http://www.freedom-to-tinker.com/?p=497
  • http://europa.eu.int/eur-lex/lex/LexUriServ/LexUriServ.do?uri=CELEX:52003AB1024(01):EN:HTML
  • http://www.cl.cam.ac.uk/~sjm217/projects/currency/
  • http://wildspark.com/eurionize/
  • Information on the Swedish 100kr note from the eagle-eyed montecarlo

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