ABSTRACT
Although the words “covert channeling” bring up for some
people images of spies and evil spirits, the meaning we
discuss in this entry is even more interesting and some-
times even more sinister.
We should note that we are not talking about stegano-
graphy, which is mostly about hiding data and not about
moving data from place to place. Hidden data can be
moved together with the object it is hidden in, but if all
such communication is also blocked, steganography just
will not help. A covert channel, however, might still be
established. To some extent, transmitting data embedded in
images via steganography in case such image transfers are
allowed would likely constitute a “covert channel” (see the
formal definitions below).