Device Keys

Device Keys play a role in the cryptographic key management procedure in the Advanced Access Content System (AACS) specification.

The MKB is generated by AACS LA, and allows all compliant devices, each using their set of secret Device Keys, to calculate the same Media Key (Km).

These Device Keys, referred to as Kdi (i=0,1,…,n-1), are provided by AACS LA.

The MKB is encrypted in a subset difference tree approach.

The path number denotes the position in the tree associated with the Device Key.

Process to obtain the Media Key, from the MKB and the Device Keys.
The subset difference tree approach in order to get the Processing Keys ; The Devices Keys are represented in purple and the letters P corresponds to the Processing Keys: the ones in green are reachable by the given Device Keys set, and the ones in red are not.