[akoboldfrying]

This is a really neat technique, well explained at your link.

Now that I understand it, I'd describe it as: For each byte, based on its bottom 4 bits, map it to either the unique "target" value that you're looking for that has those bottom 4 bits, or if there is no such target value, to any value that is different from what it is right now. Then simply check whether each resulting byte is equal to its corresponding original byte!

Not sure if the above will help people understand it, but after you understand it, I think you'll agree with the above description :)