| 摘要 |
A method for deriving past keys by using a one way function to relate an ordered sequence of keys to each other. In one embodiment, a method provides future access keys by creating a plurality of entitlement control messages, each entitlement control message including an access key for a given time period. In another embodiment, a method provides future access keys by creating an entitlement control message having a plurality of access keys corresponding to a plurality of time periods. In another embodiment, a method tracks an entitlement history by creating an entitlement management message having an entitlement time history field that includes information about whether a user has entitlement to view content recorded during a past time period. In another embodiment, the invention authorizes access to stored digital programs by determining whether a program is old, determining whether a user is authorized to view the old program, and if the user is not authorized, asking the user whether the user wants to access old programs, if the user wants to access old programs, displaying a plurality of payment options to the user.
|
