| 摘要 |
The system includes a content distribution centre which holds a plurality of items of encrypted content data and a plurality of respective keys suitable for decrypting the content data, a terminal device on which the recordable medium (e.g. a CD or DVD) is loaded and a communication link connecting the content distribution centre and the terminal device. A first session is initiated by the terminal device sending both medium information and a request for first content to the content distribution centre, the content distribution centre extracts the encrypted first content corresponding to the request, encrypts its respective first content key using at least the received medium information to form a first session encryption key and sends this, together with the encrypted first content to the terminal device, which records the encrypted first content onto the recordable medium. A second session is initiated by the terminal device sending the medium information, a request for secondary content and the first session encryption key to the terminal device, the content distribution centre decrypts the first session encryption key using at least the medium information to produce the first content key, extracts secondary encrypted content corresponding to the request for secondary content, decrypts this using its respective secondary content key, re-encrypts the secondary content using the recently extracted first content key and sends the resulting encrypted content to the terminal device, which records the encrypted secondary content onto the recordable medium. The medium information may be associated with the recordable medium on which the first and second content is stored, or it may be associated with a separate recordable medium (such as an SD card) also loaded onto the terminal device. Thus multi-session recordings can be decrypted using a single encrypted content key, rather than using a separate key for each session. |
