On 4/9/07, tedd <tedd@xxxxxxxxxxxx> 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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