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).