On 6/11/07, Jim Lucas <lists@xxxxxxxxx> wrote:
Tijnema wrote: > On 6/11/07, Robert Cummings <robert@xxxxxxxxxxxxx> 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.
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remember, change height, width, color depth, plus all possible morphing and you are talking about a lot of images. -- Jim Lucas
Convert image to fixed width + fixed height + default depth, then do some work on it :P Tijnema -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
