the EURion Constellation on banknotes

Markus Kuhn:
Photoshop CS Adds Banknote Image Detection, Blocking?:

These little yellow, green or orange 1 mm large circles have been on European banknotes for many years. I found them on German marks, British pounds and the euro notes. In the US, they showed up only very recently on the new 20$ bill. On some notes like the euro, the circles are blatantly obvious, whereas on others the artists carefully integrated them into their design. On the 20 pound note, they appear as “notes” in an unlikely short music score, in the old German 50 mark note, they are neatly embedded into the background pattern, and in the new 20 dollar bill, they are used as the 0 of all the yellow 20 number printed across the note. The constellation are probably detected by the fact that the squares of the distances of the circles are integer multiples of the smallest one.

I have later been told that this scheme was invented by Omron and that the circle patter also encodes the issuing bank.

[via Ed Felten:
Freedom to Tinker: Photoshop and Currency]

Meanwhile, here is a bad trend. From

The other disturbing part about this revelation is that Adobe admits that they don’t even know how the blocking software works. They were given the code
by the Central Bank Counterfeit Deterrence Group without details on how it works or what it really does. In other words, the software could do a lot more than blocking images of currency. I doubt it really does at this point – but the fact that they would simply dump in a software component that they don’t know what it’s really doing, and then not tell customers about it is a bit disturbing.

There are useful legal links (in eight languages) at
site run by the European Central Bank.

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