| 摘要 |
A system for restricting playback of an electronic presentation, such as a digital video or song. The system uses a playback time limit that specifies a duration of allowable playback time. The playback time limit is typically longer than the running time of the presentation so that a user is able to use standard transport controls such as pause, stop, rewind, fast forward, etc., that affect the overall playback time needed to view the presentation in its entirety. One approach uses a secure time base that is provided by a server over a network to a client device that includes a playback device. The secure time base is received and used by secure processing within the playback device. This approach allows rendering of the presentation to an output device to be performed by non-secure processing without unduly compromising the security of the system.
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