Optional ReadonlycontentFairPlay content (asset) id the license server looks the key up by, such
as the asset id of an HLS skd:// key URI. Used to start
DrmKeySystem.FAIR_PLAY_2_0 sessions.
ReadonlykeyThe key system used in the encryption.
Optional ReadonlyproPlayReady object.
Optional ReadonlypsshThe initialization key, in base 64.
Protection information for a key system. Media may have more than one protection system.