> Also, something I dimly remembered about using hard-to-forge glass spheres as physical security tokens, taking advantage of their inner structure Cool! This

> Also, something I dimly remembered about using hard-to-forge glass spheres as physical security tokens, taking advantage of their inner structure Cool! This made me remember of another, simpler technique I saw somewhere: take a bunch of different colors of sprinkles[0], mix them and sprinkle on something sticky. You now have a 2D barcode that's guaranteed (statistically) to be unique. It's also reasonably easy for a computer to scan quickly, with low error rates. Perfect for tracking individual items produced in mass quantity - in fact, I first heard about this in context of tagging individual pills in pharmaceutical products, for purposes of quality control and audit trail. The principle generalizes to confetti, colored beads, etc. of all sizes, but of course using bakery supplies gives you a food-grade stamp that you can also eat :). I think we pay too little attention to the analog world these days; plenty of fascinating inventions can be made by applying computer technology to shift complexity from code into structure of physical objects. -- [0] - https://en.wikipedia.org/wiki/Sprinkles https://en.wikipedia.org/wiki/Sprinkles