Blogger and hacker, Janne, has published a blog post exploring banknote validators, and how they work.
There are dozens of different security features embedded within authentic banknotes, designed to prevent counterfeiting and make it easier for validators to check the genuine articles.
These include microprinting, UV and IR dyes, holograms, colour-changing inks, watermarks, security stripes and ridges, and special paper.
The blogs details how these validators work, and while they appear fairly generic from the outside, they all seem to share common sensor hardware and a complex algorithm to test permeability, brightness and reflectivity.
Many of these sensors are used to test the same features in the banknote, giving it a degree of redundancy and ensuring the smoothest operation possible.
However, this also means that it’s possible to create a fake bill that passes validation, by ensuring all the sensors are triggered during the validation process.
