Has this photo been de-stegoed? (and Clouds)

Major Variola (ret) mv at cdc.gov
Thu Dec 11 15:23:33 PST 2003


At 02:35 PM 12/11/03 -0500, Tyler Durden wrote:
>Variola wrote...
>
>"How do you know the signature of the unaltered carrier-medium?
>E.g., have you measured the LSBit noise from my camera recently?
>Under which lighting conditions?"
>
>Well, having done some optical signal processing (and getting a patent
in
>that area, come to think of it), I imagined that most photos will
naturally
>have some image noise in certain frequency bands...

You are *way* too FT based in your thinking.  There are *many* other
measurements and statistics and co-relations.

And the noise I was referring to is in part electronic noise, not image
noise
in either the spatial freq. or poisson sense.  The point being that
there is
info that is perceptually insignificant, that you can replace with
compressed encrypted bits.





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