I love browsing the blogs at datagenetics. I had never heard of visual cryptography until I read this page:
It’s a way to combine pixelated images to make another image. I have yet to research color visual cryptography, so for now all pictures need to be two color. Let’s take the following Judas Priest images I’ve converted to black and white.
I wrote a program to encrypt the images, so that you can ‘combine’ two of the images to make the third. You don’t need to use two images to make a third; you could just have two ‘white noise’ images to make the final image, but this is more fun. That the top picture will move with your mouse – no clicking necessary. Just slide the image on the top over the one at the bottom to reveal the third picture.
Pretty cool, huh?
After writing that program, it occurred to me that it would be possible to use one encrypted image as a key to reveal images on different encrypted images. So I wrote a program to do that. The end result is five images of a Kiss logo, but when one of them is placed on any of the others, you’ll get a picture of one of the band. (Images found on the net that I converted to black and white.)
Your mouse will move the top image over the others. Move it until it’s directly on top of the other images. If you’re within ten pixels, a hint will pop up to tell you which way to go. Lest you think there’s some kind of trickery afoot, download the pics and line them up yourself.
This was mostly an exercise in converting images to black and white (and keeping with the band theme). It’s more of an art than a process.
I’m currently working on how to make physical versions. The problem is that the images have to be lined up EXACTLY, and at their current resolution, that means within a fraction of a millimeter. Rather than hold up this post, I’ll label this Part One and post any successful results later (and/or fails).
I’m posting the software I wrote. Mind you, I didn’t write it with end users in mind, I wrote it to get results. There’s not really any error trapping, so there’s a probability it might crash on you if you do something it doesn’t expect. But if you start it again, is should work. For best results convert the images to black and white and make them all the same pixel size. Drag and drop the images on the appropriate areas; that’s the only input for pictures.
Download Visual Cryptography – 1.2M
Download Visual Cryptography – One Key – 1.2M