contentKey
Decrypt the content key using the device's encryption key.
The license encrypts a 32-byte block to the device: the first half is an integrity key that authenticates the whole license, the second half is the content key. A scalable license interleaves the two and wraps the real key behind an auxiliary-key derivation instead.
Throws
if the license is for another device, or uses a cipher this CDM has no key for
if the license's integrity CMAC does not match