The invention relates to a cryptographic method secured against a covert channel attack.
The encryption unit may filter, convert or reject predetermined commands or types of information in the header to prevent covert channel transmissions.
Therefore, the side-channel can be used as a hidden channel for copy protection purposes.
The outlet (9) of the blind channel (7) and the inlet (10) of the through channel (4) are disposed onto one lateral face of the body.
An orientation (74) of the hidden channel (66) is determined as a function of the first and the second distances.
According to one aspect of the invention, at least one object (30) which comprises a hidden channel (66) having a visible entry opening (72) is located in the area of space.
In order to efficiently prevent the save-and-restore attack on usage rights associated with digital work, these usage rights are protected by a hidden channel.