It really wouldn't. Take the average of the puzzle, if it's 75% grey in a wide distribution then move it a bit, repeat until there's some huge change in the histogram. Easier to solve than most I've seen.
Pixels are OR'd, so you'd want 75% grey, not 50% (assuming each of the component images is an even distribution of white and black pixels). Otherwise, yeah.
Actually it is a terrible CAPTCHA; no normal human will understand why the hell is he supposed to drag those noisy rectangles, while machine will easily find hidden image by scanning and counting entropy.
Yes and no. I'm the inventor of a Google-owned patent (http://www.google.com/patents/US8397275) using N layers of partially transparent images, and JavaScript to generate the offsets between the layers.
The CAPTCHA can be hard to read. (Note that for one of the images in the patent, the lawyer used a Gaussian blur rather than ask me for another screen shot from the prototype.) It might also confuse the user, because they see white noise when the CAPTCHA is first loaded.
The plus side is that it's a simple way to bring JavaScript into the CAPTCHA and force an attacker to create a high fidelity emulation of a browser, hook into a browser, or else take periodic screenshots in hopes of getting the CAPTCHA in its readable state.
Basically, I used to work on JavaScript execution in Google's indexing system, and thought "man, this is a pain to get all of these corner cases just right... how could I force a CAPTCHA attacker to do this?"
“There will be no banner ads on the Google homepage or web search results pages. There will not be crazy, flashy, graphical doodads flying and popping up all over the Google site. Ever.”
TOMODO.com Interesting Idea but I think I’ll pass… All my HN clicks views and votes would go through your site first. You know I’m just not that trusting. Not to mention with mass adoption it could render HN’s algorithms useless.
Foresee successfully moved to have the venue changed to Northern Illinois and still settled... I think it's more than the location. It's the system that's broken!
Incorrect. The cat doesn't depend on your validation of its status; if you feed it, you just increase the chance that it thinks you are a subject worthy of its time and attention.
