| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of descrambling a scrambled data object. SOLUTION: At least a section of the scrambled content data object is descrambled by applying a decryption operation under a key derivable from a content descrambling key. At least one content descrambling key is obtained from a message received from a conditional access sub-system over a data communication channel. A cryptogram of data obtainable from at least one content descrambling key in the message, each of which cryptograms are carried in the message, is decrypted under an associated channel key. A first key is used to establish each channel key. At least the section of the scrambled content data object is descrambled by applying a further decryption operation under a key derivable from the first key. COPYRIGHT: (C)2007,JPO&INPIT |
