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From: john@anasazi.UUCP (John Moore)
Newsgroups: net.dcom
Subject: Re: Hidden information in datacomm
Message-ID: <611@anasazi.UUCP>
Date: Tue, 4-Mar-86 09:45:46 EST
Article-I.D.: anasazi.611
Posted: Tue Mar  4 09:45:46 1986
Date-Received: Sun, 9-Mar-86 08:26:22 EST
References: <3031@ncsu.UUCP>
Reply-To: john@anasazi.UUCP (John Moore)
Organization: Anasazi, Phoenix Az.
Lines: 27

In article <3031@ncsu.UUCP> hes@ncsu.UUCP (Henry Schaffer) writes:
><>After reading the discussion on how the inter-character distances
>of a printout (easy to do on a laser printer) could be used to encode
>information, I started thinking about other places to hide information.
>  One place I came up with can hold quite a bit (pun intentional) of
>information is the stop bit of serial ascii transmission.  (One can
>consider this another example of inter-character distances.)  It
>wouldn't take very much special in the way of extra hardware to 
>generate a few different lengths of stop bits (e.g., 1, 1 1/4, 1 1/2,
>and 1 3/4 bit timings long) and to differentiate between them at 
	One tries to design optimal filters for modems based on the
signalling speed. Thus, if you are using a 1200bps modem, the data
filters (which are essential for improving the signal to noise ration)
will cut off information above the 1200bps rate. The different lengths
of stop bits correspond to increasing the baud rate of the line (they
add higher frequencies to the baseband signal. Hence, the better the
modem you use, the worse this technique will work!
-- 
John Moore (NJ7E/XE1HDO)
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The opinions expressed here are obviously not mine, so they must be
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