| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an improved method and an improved receiver for obtaining a control word. <P>SOLUTION: Two or more subkeys are obtained in a receiver. Each subkey is encrypted, under control of a key received in an entitlement message or transformed under control of a seed received in an entitlement message. After decryption or transformation, the subkeys are combined to obtain the control word. Typically, at least one of the entitlement messages is a positive entitlement message and at least one of the entitlement messages is a negative entitlement message. The present invention can be used in a conditional system, such as Pay-TV system. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
