An artistic pattern that conceals a subtle test could foil forgers who copy the security print used on concert tickets, rail passes and CDs (US 2003/0157305).
Nigel Abraham, the British inventor who dreamed up the idea, says the pattern contains several dozen small stars, some with 30 points and others with 31. The brightness of the stars also varies slightly in a way that encodes information about which have fewer points. These differences are subtle and so cannot be copied conventionally using digital scanning or photocopying.
A special scanner picks up the encoded information and also counts the points…
