The prisoners' problem, in which two individuals attempt
to communicate covertly without alerting a warden who
controls the communications channel, has taken a number of
forms, adorned with various assumptions which make the
problem more or less difficult. One assumption which makes
the problem considerably more managable is that the
participants are allowed to share secret information (such
as an encryption key) prior to imprisonment. Another
assumption, which makes the problem much more difficult, is
that the warden be allowed to modify messages sent between
the prisoners as well as read them. This paper describes
how a certain kind of communications channel would allow
pure steganography, in which no secret information needs to
be shared before imprisonment, even in the presence of an
active (content-modifying) warden.
By: Scott A. Craver
Published in: RC20931 in 1997
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