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Messaging Over IPv6 Headers
elias miles writes "A guy from the Swiss Unix Users Group made a cool utility that lets you chat over IPv6 packet headers. Not useful, but it's a nice hack.
Read the article and download joe 6 pack."
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that would be security through obscurity - which we all know can not be relied on.
The point of a covert channel is obscurity. You could add security on top of it, but putting the message into the data part would defeat the whole purpose of the covert channel. You are trying to find some way to get processes/machines/people to communicate within the confines of the operating system, and without anything/anybody else knowing about it.
An simple example? Say all the normal channels for process communication are blocked. No pipes, no sockets, etc. You can't use files. The only thing you can do is monitor the activity of the other process (ie the 'ps' command). By monitoring, say, memory allocation of the other process, two processes could communicate, sending the data byte by byte. Once a byte is sent, the receiving process could increment its memory to confirm. Then the sender increments its memory to send the next byte, etc.
The point of covert channels is that no matter how secure a system appears to be, it is possible for leaks because of things like this (probably more complex).