From: norm@netcom.com (Norman Hardy)
Date: Mon, 28 Feb 94 21:23:12 PST
To: cypherpunks@toad.com
Subject: Re: standard for steganography?
Message-ID: <199403010523.VAA00389@mail.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


Has anyone done statistical studies of low bits of pixels or sound samples?
I suspect that they are often far from random. A flat 50% distribution in
the low bits might standout like a sore thumb. I can imagine the the low
bit can be distributed dependently on such things as the next to low bits
or 60 cycle power at the recorder. Some AD converters are known to produce
60% ones or some such.  Like mechanical typewriters, AD systems probably
have there own idiosyncrasies. Given a flat stream of cipher data, there
are techniques to reversably introduce such variations to mimic the biases
of real AD converters without much data expansion.

It is my wild guess and conjecture that with such statistical variation
built in there would be no effective statistical test for a given file
containing hidden messages.