| 摘要 |
A communication system for point-to-point communications of content such as video files in a video on demand system employs one or more keys specific to a user. Upon receiving a request including a specific user ID for a content, the transmission end uses the specific key corresponding to the user to encrypt control words that are transmitted to the user, to encrypt control words before they are used to encrypt the content at the transmission end, to encrypt the content itself, or some combination of the foregoing. A user unit performs the reverse operation using one or more specific keys stored in the user unit and/or a security module associated with the user unit. The user unit also uses a specific key to encrypt any content that is stored at the user unit. |
