2. Hidden channel

Now that the framework for executing a process has been defined, let's look at what a covert channel is: a covert channel is a communication path that was not initially intended and/or is not authorized for transferring information, and which therefore violates the security policy in place. It should be noted that a covert channel therefore requires at least two participants: the one giving the information and the one receiving it.

Let's take the example of a user on a system who wishes to use software on that system. However, he does not trust the software, as it could redistribute the information supplied as a parameter to the software (for example, a cost calculation or a tax return). Nor does the software designer wish to reveal how the software works.

The aim is to create an instance of the program that the user will trust, that will...