Maybe no stego on eBay afterall

[bear]

On Fri, 19 Jul 2002, Peter Wayner wrote:

>
>I used to think that CCD cameras were a pretty good approximation of
>random number generators, but not any longer. I've seen too many
>pictures where the LSB is heavily correlated with some of the higher
>order bits. Really. There are some good pictures documenting in my
>book. So while I think you're making a fair point, experience doesn't
>always suggest that it work out that way.
>

If the pictures are scaled ("digital zoom" anyone?) or smoothed, the
pixel values (including the LSB's) turn into a system of fairly simple
linear equations relating adjacent pixels.  This might be the effect
you're seeing.  Of course, you could also be seeing hardware that
creates this very correlation as some side effect of the way it works,
too.  But in a scaled or smoothed image, where the pixels are literally
the output of simple linear equations, any "randomness" sticks out
like a sore thumb.


				Bear


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