EURion constellation

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Image:EURion.png Image:EURion20GBP.JPG Image:10e rec.png A number of recent banknote designs contain a pattern now known as the EURion constellation. It is added to help software detect the presence of a banknote in a digital image. Such software can then block the user from reproducing banknotes to prevent counterfeiting using colour photocopiers. The name was coined by Markus Kuhn, who discovered the pattern in early 2002 while experimenting with a Xerox colour photocopier that refuses to reproduce banknotes. The word is a portmanteau of Orion, a constellation of similar shape, and EUR, the Euro's ISO 4217 designation.

The EURion constellation first described by Kuhn consists of a pattern of five small yellow, green or orange circles, which is repeated across areas of the banknote at different orientations. Andrew Steer later noted simple integer ratios between the squared distances of nearby circles, which gives further clues as to how the pattern is meant to be detected efficiently by image-processing software.

The EURion constellation is most prominent and was therefore first recognised on the 10 Euro banknote. It was then also found on

all Euro banknotes (since 2002);
German Deutsche Mark notes (1996–2002);
British banknotes;
United States
- $10 (since 2006, both sides),
- $20 (since 2003, back side),
- $50 (since 2004, back side) bills;
Danish Krone banknotes (since circa 1998);
Canadian bills (all of the 2001 series);
South African Rand banknotes (2005 series);
Australian 2001 commemorative $5 note;
Japanese yen banknotes;
- ¥2000 (Commemorative series D, 2000, both sides)
- ¥1000, ¥5000 and ¥10000 (Series E, 2004, both sides)

Some banks integrate the constellation tightly with the remaining design of the note. On German banknotes, the EURion circles formed the innermost circles in a background pattern of fine concentric circles. On the front of British £20 notes, they appear as green heads of musical notes. On U.S. dollar bills, they form the digit zero in little yellow numbers that show the value of the note.

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Other banknote detection mechanisms

Image:PSP-CDS.gif Users of recent versions of image editors, such as Adobe Photoshop or Paint Shop Pro, discovered that these also refuse to print banknotes. According to an article in Wired magazine, the banknote detection code in these applications, called the Counterfeit Deterrence System (CDS), was designed by the Central Bank Counterfeit Deterrence Group and supplied to companies such as Adobe as a binary module. However, experiments by Steven J. Murdoch and others showed that this banknote detection code does not rely on the EURion pattern. It detects other features of banknote designs that have yet to be described in public.

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References

Markus Kuhn: The EURion constellation. Security Group presentation, Computer Laboratory, University of Cambridge, 8 February 2002.
Mitsutaka Katoh, et al.: Image processing device and method for identifying an input image, and copier scanner and printer including same. OMRON Corporation, Template:US patent.

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