Re: MD5 & bot Question

On 4/9/07, tedd <tedd@sperling.com> wrote:

At 4:39 PM -0400 4/9/07, Robert Cummings wrote: On Mon, 2007-04-09 at 22:27 +0200, Tijnema ! wrote: This is exactly what tedd did in his last arrow example. He edited the

header of the GIF image, and so that would result in different MD5. Finding this part and skipping it in the MD5 check would do the job. :)

Yep, that's an obvious solution since it's the same way virus signatures are matched. The entire image needs some kind of permutation. Passing a couple of curved ripples across the image as a transformation, and in different directions should suffice to obfuscate the image signature without obfuscating the image itself :) Similarly watermarking the image using fractal patterns should also provide good noise. Cheers, Rob. Rob: It doesn't need to be complicated, just random placed pixels on the image from a selection of colors would provide millions of permutations. Cheers, tedd

But then OCR would still work, as when somebody scans a document, there are also some "not white" pixels. Tijnema

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