EURion

The post € Banknotes Bombing has raised some questions. Some people wrote to me reporting that Photoshop refused to scan banknotes (not just euros), while others told me they'd managed to scan them without any problems, but then the printer refused to print them.

There is indeed a system developed by the Central Bank Counterfeit Deterrence Group (CBCDG) that allows banknote images to be identified in order to make life difficult for counterfeiters. The system's official name is Counterfeit Deterrence System (CDS) and was developed at the request of the CBCDG by Digimark Corporation, a watermarking company.

CDS has existed since the late 1990s (around 1996), and its operation has never been officially disclosed. It has been incorporated by several software vendors. The currently known ones are Adobe, starting with Photoshop CS (it wasn't included in previous versions), and Jasc (Paint Shop Pro). Both claim to have received the routines in the form of precompiled code and therefore are unaware of its operation.

Many more hardware manufacturers have incorporated it into their machines' firmware. It's found in many Xerox color copiers and some HP printers.

The existence of CDS was discovered in 2002 by Markus Kuhn. While investigating a Xerox copier that refused to print an image of banknotes, Kuhn identified a symbol consisting of a pattern of five yellow, green, or orange circles, repeated in areas of the banknotes with different orientations. Andrew Steer later noted a simple integer ratio between the squares of the distances of neighboring circles, which provides further insight into how the pattern should be efficiently detected by image processing software.

The shape of the pattern is visible in the figure alongside, but it can also be seen with various rotations. Given its vague resemblance to the Orion constellation and the fact that its use received a strong boost with the creation of the Euro, the pattern was given the name EURion.

Many countries have adopted the EURion. In addition to being present on all euro banknotes, it is also printed on the Bulgarian lev, Canadian dollar, Danish, Norwegian, and Swedish krona, Hungarian forint, Japanese yen, and others (complete table here as of today).

In some color photocopiers, the mere presence of five of these circles in an image is enough to refuse to print, while others print but superimpose the wording "specimen" or "facsimile" on the image, even if the resulting image has significantly different dimensions or colors from the original. For example, I have a notebook whose pages are 100,000 lire notes printed with "Facsimile," but the size is significantly different from the actual note and the printing is on only one side. Furthermore, the EURion sometimes causes problems even for honest users. Advertising designers, for example, have often complained about the inability to scan banknotes into Photoshop, so much so that some central banks allow users to download high-resolution banknote images with some details modified.

It's also interesting to see how the EURion was incorporated into the banknote. It's usually not immediately recognizable. Sometimes it becomes so once you know what to look for.

The most obvious example is the €10 note (below, left, click to enlarge) featuring many small circles, some of which form the EURion. In other notes, the pattern is less visible. In fact, sometimes the circles are clearly visible, but go unnoticed because they are part of a larger design. For example, on the $20 note, various copies of the pattern, with different rotations, are created using the zeros of the continuously repeated "20," while on the old £20 note, dedicated to Elgar, the pattern is obtained by joining the notes of a fragment of score.

Lately, however, more careful research has shown that EURion is not the only banknote recognition scheme. While photocopiers continue to rely on EURion, software such as Photoshop and Paint Shop Pro also use other systems, as demonstrated by this research.

Back