Singapore’s Bank Notes Have a Top-Secret Symbol on Them.

It’s the early 2000s. 

The era of knowledge and the internet is fast dawning on most of the world. The dotcom bubble is at its height, with start-ups popping up here, there and everywhere. Windows XP is king and Myspace is the dominant social media network. In this climate, the researchers at one of Cambridge’s industrial labs receive a new Xerox colour photocopier. Markus Kuhn, a computer science PhD student, rushes down to try out the state of the art contraption. 

He places a £20 note into the machine to scan, presses the copy button, and waits. The paper stutters and churns its way out. To his surprise, instead of getting a print of the queen’s face in purple, a message manifests in various languages, telling him that copying money was illegal. Undeterred, he tries again, with a 10-euro note — same result. This surprises him. How does a printer, which isn’t connected to the internet, recognise what is a banknote and what is not?  

After staring at the Euro for a while, he sees a seemingly random pattern of circles. He checks the £20 — it too has the pattern, albeit hidden as the heads of musical notes. Determined that the circles have something to do with the anti-counterfeiting message, he draws the pattern of circles out on a paper, and tries to photocopy it. When he does this with a black pen, the page gets perfectly replicated. On the other hand, when he uses coloured markers – success – the legal message gets printed. 

The EURion Constellation, as Kuhn called the symbol, has since been discovered on most major currencies. 

Including the Singapore dollar. 


An EURion Constellation block. (Source)

Details about the EURion constellation are kept secret by its inventors and users. No one actually knows who created it, who licences it or what its actual name is. 

Some hypothesise that the pattern and detection algorithm were designed at Omron Corporation (the Japanese company that is best known for its message chairs). In a 1995 patent application, Omron covets an invention that “concerns an image processing device and method for identifying an input image ideally suited for scanning documents which may not be copied, such as bank notes or negotiable securities, and preventing a copier from printing out copies of them”. A 2005 Reserve Bank of India press release also called the security measure, an ‘Omron anti-photocopying feature’. 

The EURion Constellation on the S$10 note.

Singapore seems to be one of the earlier adopters of the EURion constellation, with the feature first appearing in the 1999 portrait series of notes. The circles can be seen in the top right hand corner of the notes, beside Yusof Ishak’s face. Following Singapore’s lead, the Japanese Yen adopted the feature in 2000, the Euro in 2002,  and the US Dollar in 2006. As of June 2019, up to 55 currencies have the rings, many disguised in clever ways. On some U.S. bills, they appear as zeros in small, yellow numbers matching the value of the note. On the Japanese Yen, these circles sometimes appear as little sakura flowers.

How Does it Work?

When it comes to anti-counterfeiting measures, secrecy is key. Think about it, if information about security measures are readily available, they could be easily reverse-engineered, rendering them ineffective. 

This is precisely why little is known about the mechanics of the EURion constellation. Some allege that the scanners look out for the specific distances between the five circles. Others argue that colour is more important in the detection process. In a 2011 press release, an Indian central bank explained that the circles show up in a different colour to that seen by the naked eye, when lit up by the scanner. If this is true, it explains why Kuhn’s Xerox printer only recognised the rings when he used a coloured pen.

Warning that appears when you try to import a Singapore Dollar note into Photoshop.

It’s important to note that the EURion constellation might be a part of the more comprehensive Counterfeit Deterrence System (CDS). Designed by the Central Bank Counterfeit Deterrence Group (CBCDG) – a group of 27 Central Banks – the system is included in image editing software like Photoshop and Paint Shop Pro. So, if you try to edit bank notes on these apps, you are likely to get an error message telling you that it’s illegal to edit the design of currencies. While the EURion constellation might be a part of this system, digital watermarks invisible to humans are also embedded in images of currency. Digimarc, the company believed to have created the technique, also has patents that describe a method to secretly record whether a photo editing user has been working on images of currency. In the real-world context, this means that police and other law enforcement agencies can tap into computers to gather evidence against counterfeiters.  However, in a 2015 interview with the BBC, Pierre Laprise, the director of the CBCDG, has distanced the organisation from this method of recording, stating privacy concerns.

Law and Order

Currency laws in most countries are strict and comprehensive. The United States for example has 32 pages of laws relating to currency, and in most countries, the very act of trying to photocopy bank notes is illegal. Besides this, even print and electronic illustrations of currency is highly governed. Back home in Singapore for example, if a production crew wants to use fake money for a movie, they must:

  • Print at least 150% of both the length and width of the genuine currency note when the reproduction is enlarged, or no more than 60% of both the length and width of the genuine currency note when the reproduction is reduced in size;
  • Use the word ‘‘SPECIMEN’’ in black and bold lettering diagonally across the reproduction if the money is shown from a top-down, flat perspective.
  • Not carry out duplex printing (i.e. nothing shall appear on the reverse of the reproduction that may give the impression that it is a genuine currency note).

Don’t Try This at Home

Most experts agree that it is easy to circumvent these security features, but that’s not the point. Measures like the EURion constellation are not meant to eradicate counterfeit money altogether. They are meant to stop amateurs from trying their hand at counterfeiting. In this scenario, a central bank has to track down hundreds or even thousands of counterfeiters from around the country.

This is obviously much tougher than punishing dedicated syndicates of criminals. 

In a world that is bubbling with clickbait, sensationalism and oversimplifications, Kopi aims to bring long-form journalism back to South-East Asia.

Through deeply analysed articles, we uncover and explain the complex and multifaceted issues facing our societies. Through engaging narratives, we tell stories that are bold and unique.

More Stories
How a Top-Secret WW2 Raid Into Singapore Went Horribly Wrong