I want you guys to check something out, because this is actually pretty neat.
Last month, there was a blog post on DataGenetics about visual cryptography, and how it worked. Go to the page and at least give the examples a go.
Its workings are explained in detail on that page, but it boils down to splitting up each pixel into four parts (2×2, but other sizes will work as well), then dividing those over two layers. Arrange these parts correctly on separate layers, and they’ll show your image when overlaid.
Real cool to see how, as you shift one of the layers a little bit, the image appears to rise from a bunch of noise. Wasn’t there something similar back in the day, a toy that used punched cards or something?
I can see some useful applications though. It’d make for a nice anti-bot measure, way cooler than any old captcha you’ll find around. These things might prove to have some worth in puzzles, too. Imagine a mystery treasure hunt thing. You’ll obtain both cyphers along the way, but still need to figure out how to use them to unlock their message! They both look like random noise, after all.
Interesting stuff, eh? What would you use it for?