| 摘要 |
The present invention controls copying of an information signal, comprises the steps of prior to recording and/or transmission, applying to the information signal a substantially imperceptible modification representing copy control data including a password securely encoded according to a predetermined algorithm; upon reproduction for copying by a user, deriving (S 1 , S 3 ) the copy control data from the modified information signal; comparing (S 8 , S 9 , S 11 , S 13 , S 15 ) the derived securely encoded password with a reference password securely encoded according to a predetermined algorithm; and enabling (S 5 ) copying of the information signal if the securely encoded password derived from the information signal and the securely encoded reference password have a predetermined relationship, otherwise disabling copying (S 7 ). The reference password is sent to the user via a channel, which is separate from a channel used to send the information signal to the user.
|
