Re: Going from simple to super CAPTCHA

Tijnema wrote:

On 6/11/07, Robert Cummings <robert@interjinn.com> wrote:

On Mon, 2007-06-11 at 10:38 -0400, tedd wrote:

Gnag: I know we can beat this thing to death, as we have in previous threads and I don't anyone wants to travel previously traveled ground. However, Rob said: "A good captcha will try to exploit a computer's weaknesses." So, let's expound on that -- what do you consider to be a computer's

weakness? Well for instance as humans we can fairly easily recognize similar shapes. We can recognize an apple whether it is red, green, yellow, has a stem, has a leaf, is half eaten. A computer might recognize a circle, and might guess that the circle is an apple based on further analysis. But we as humans could recognize it as an apple even if we stretched it a bit so it was no longer circular, or as I said, if it was a crescent because someone had taken a huge bite out of it. This is something humans excel at... inferring information from similar previous experiences. Taking the image captcha to a different level, one could combine our ability to understand language as well as imagery. For instance we could have an icon repository of animals, vehicles, plants, etc (very obvious ones anyways). Then to create a captcha we could randomly select X icons, slightly morph them to spoof matching them within the captcha image itself, then ask: What animal do you see in the above picture? I think someone already said microsoft or someone does something similar. The principle is that we know what generally constitutes an animal and a computer does not. Similarly, an audio complement would be to have a background sound of maybe low level radio chatter overlaid with the sounds of various everyday items... then one could ask: What did you hear ringing? Possible answers... a bell, the telephone, an alarm, etc. The problem then becomes an issue of people who can't spell or are terrible at recognizing everyday things. Cheers, Rob.

Server builds up a database of pictures, client does the same with MD5 check, and problem solved...:) Tijnema

not if you are morphing/changing the image each page load. Personally, I would not save the images that I have already morphed. Granted, this would put a little more work on my box, but I think it is a price I would be willing to pay if it would prevent someone from storing all possible image/md5 sums. have fun storing all my randomly morphed images from here to infinity. remember, change height, width, color depth, plus all possible morphing and you are talking about a lot of images. -- Jim Lucas "Some men are born to greatness, some achieve greatness, and some have greatness thrust upon them." Twelfth Night, Act II, Scene V by William Shakespeare