On Tue, April 10, 2007 7:47 am, tedd wrote: > Your use of metaphor is quite colorful, but if you if change a single > pixel in an image, then you change the MD5 signature -- that is what > I was talking about -- and that is not wrong. Unless I look at enough images to figure out that you are just changing N random pixels, and I construct a "distance" function to compute how "different" image A is from image X, where I already know X points "up" http://php.net/imagecolorat can be used to do exactly this. In fact, I've done that to break a CAPTCHA that had random "noise" pixels added to the text. Actually, I was able to remove the "noise" first and then compute distance function for character by character analysis of the text on the image. I do not understand why you are obsessing on the MD5 "crack" when it's probably not the weapon that would be chosen, unless your CAPTCHA is so lame that it's susceptible to an MD5 crack... If it's not that lame, then the attacker just doesn't use an MD5 signature, and employs another technique. Have we not been through this whole thread enough times already? -- Some people have a "gift" link here. Know what I want? I want you to buy a CD from some indie artist. http://cdbaby.com/browse/from/lynch Yeah, I get a buck. So? -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
