From: Spike Jones (spike66@attglobal.net)
Date: Wed Sep 19 2001 - 21:32:44 MDT
Harvey Newstrom wrote:
> Robert Coyote wrote,
> > But is it still possible to detect steganographic messages if the amount
> > of information encoded is very small, compared to the amount of
> background?
>
> Remember that standard graphic algorithms, such as GIF or JPEG, use industry
> standard mathematical algorithms to compress data and smooth insignificant
> variations. It is easy to use these algorithms to predict how color should
> have been smoothed and to detect bits that deviate from the expected values...
I can think of a way to bust this. Take a 256 color JPEG, unmodified
in any way. Take your message, convert it to ASCII. Search for the
first character in the photo, record the position of that byte, proceed
to the second, etc. Granted you need a really colorful photo to make
this work, such as a Mardi Gras celebration. When you are finished,
PGP encode the character string that tells the decoding program where
to find each pixel, which it converts back into the message. Once again
you have a photo in which one cannot prove an encoded message
exists.
Does this algorithm have a name? spike
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