On 4/9/07, tedd <[EMAIL PROTECTED]> 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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