Patent ID: 8842823

Claim:
A method for determining usage of encrypted media content encrypted with separate short-term keys in at least two hierarchical layers, wherein the hierarchically higher layers depend on hierarchically lower layers, the method comprising: Obtaining media content of a base layer (BL 1 ) encrypted with a first short-term key (K 1 ); Obtaining media content of a first enhancement layer (EL 1 ) encrypted with a second short-term key (K 2 ); obtaining short-term keys (K 1 , K 2 ) for decrypting the media content in at least two hierarchical layers, wherein the at least two hierarchical layers comprise at least one Base Layer (BL 1 ) and at least a first Enhancement Layer (EL 1 ), wherein Layer EL 1 depends on layer BL 1 ; obtaining at least one long-term key for decrypting the short-term keys, wherein the short term keys are valid for a shorter period of time than the at least one long-term key; decrypting the short-term keys based on the at least one long-term key; decrypting at least one hierarchical layer of the media content based on at least one of the decrypted short-term keys; logging usage of at least one of the short-term keys as a basis for determining usage of the media content; and logging a parameter relating to the short-term key of at least one hierarchical layer.