Efficient collusion attack-free access control for multidimensionally hierarchical scalability content

This paper proposes an efficient access control method for content with multiple dimensions of hierarchical scalability. The proposed method versatilely serves various quality content by simultaneous control in every dimensions of scalability. This method manages single entity for the content and single encipher key, though it prevents users from colluding. A user receives single ciphered content and single decipher key to obtain the content with the permitted quality. In comparison to the conventional collusion attack-resistant access control methods, the sophisticated key generation manner in the proposed method reduces the required length of the managed key and that of the managed codestream.