Device Keys

Device Keys play a role in the cryptographic key management procedure in the Advanced Access Content System (AACS) specification. This specification defines a method for protecting audiovisual entertainment content, including high-definition content.

Device Keys play a role in the cryptographic key management procedure in the Advanced Access Content System (AACS) specification. This specification defines a method for protecting audiovisual entertainment content, including high-definition content. Each compliant device is given a set of secret Device Keys when manufactured. The actual number of keys may be different in different media types. These Device Keys, referred to as Kd i (i=0,1,…,n-1), are provided by AACS LA. The set of Device Keys may either be unique per device, or used commonly by multiple devices. A device shall treat its Device Keys as highly confidential. The MKB is encrypted in a subset difference tree approach. In order to decrypt it, a device must know the right Processing Key (P) which is available via the subset-difference tree process. Essentially, the set of Device Keys are arranged in a tree such that any given Device Key can be used to find lower level Processing keys. The processing keys at higher position in the tree than the given set of Device Keys are not reachable. A given set of Device Keys gives access to a given set of Processing keys. This way, to revoke a given Device Key, the MKB needs only be encrypted with a Processing Key which is not reachable by its Device Keys set. ==See also== History of attacks against Advanced Access Content System AACS encryption key controversy Guide to understand AACS

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