| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a safe transfer method of a secret key for decrypting encrypted data in a broadcasting system of conditional access contents. <P>SOLUTION: A server transmits an encrypted content to a receiver together with an encrypted control word. The server comprises a reference time counter and verifies whether or not the receiver sends back a verification message within a predetermined window by using a return communication path. When the verification is positive, the server sends back a key message including key information for encrypting the control word to the receiver. The receiver extracts the key information from the key message, decrypts the control word, and decrypts the encrypted content. <P>COPYRIGHT: (C)2012,JPO&INPIT |
