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----- Original Message -----
From: <hal@finney.org>
To: <extropians@extropy.org>
Sent: Wednesday, September 19, 2001 10:24 PM
Subject: RE: steganography
> Harvey writes:
> > 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.
> > The whole theory behind color smoothing is that any given bit might be
> > random noise which should be overridden with calculations based on its
> > neighbors. The same algorithms can be used to detect these bits that
have
> > unexpected values.
>
> There is one program which is supposedly undetectable at embedding data
> into JPEG images. http://www.outguess.com has some very sophisticated
> statistical analysis behind it (see the papers on the web site).
> The author has shown how to detect all the other JPEG embedders and
> has constructed his software to be undetectable by the best methods he
> could come up with. So far I am unaware of anyone showing how to detect
> data embedded using his technique.
>
> Hal
>
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