Secure clock with grace periods

• US 20060248596A1
• Filed: 04/27/2005
• Published: 11/02/2006
• Est. Priority Date: 04/27/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Cutter, Banjamin B. Jr., Jain, Amit, Strom, Clifford P., Evans, Brian P.
• Granted Patent: US 8,438,645 B2
• Time in Patent Office: Days
• US Class Current: 726/27
• CPC Class Codes: G06F 21/1073 Conversion
• CPC Class Codes: G06F 21/725 operating on a secure reference time value
• CPC Class Codes: G06F 2221/2137 Time limited access, e.g. to a computer or data

Abstract

A system of controlling playback of digital media. A system of controlling playback of digital media comprising a CE device having a secure clock and a license having a specified grace period disposed upon the CE device in which a digital media file governed by the license may be played for the grace period upon failure of the secure clock.

Claims

1. A system of controlling playback of digital media comprising:

a CE device having a secure clock; and

a license having a specified grace period disposed upon the CE device in which a digital media file governed by the license may be played for the grace period upon failure of the secure clock.

2. The system of controlling playback of digital media of claim 1, in which the CE device periodically sets the secure clock by synchronizing with a trusted time authority.

3. The system of controlling playback of digital media of claim 1, in which the CE device checks to see if the secure clock has failed prior to playing the license having a specified grace period.

4. The system of controlling playback of digital media of claim 1, in which a grace period mode is entered in the CE device upon failure of the secure clock.

5. The system of controlling playback of digital media of claim 3, in which the CE device periodically records a last known good time in a secure store.

6. The system of controlling playback of digital media of claim 5, in which the CE device sets the secure clock to the last known good time after failure of the secure clock.

7. The system of controlling playback of digital media of claim 6, in which the grace period is reduced as time progresses from the last known good time.

8. The system of controlling playback of digital media of claim 1, in which the license is a time based license.

9. A method of maintaining playback on a CE device upon failure to synchronize to a trusted time authority comprising:

checking to see if a clock of the CE device was reset;

setting the clock to a last known good time if the clock has ever been set; and

checking to see if the clock is in a grace period mode.

10. The method of maintaining playback on a CE device upon failure to synchronize to a trusted time authority of claim 9 further comprising saving a grace period start time if the CE device is not in grace period mode.

11. The method of maintaining playback on a CE device upon failure to synchronize to a trusted time authority of claim 9 further comprising continuing in the grace period mode if the CE device is not previously set to the grace period mode.

13. A method of providing a grace period comprising:

getting a clock state from a CE device;

checking to determine that a clock of the CE device is currently reset;

checking to determine that the clock of the CE device has ever been set;

setting the clock of the CE device to a last known good time;

determining that the CE device is currently in a grace period; and

saving a grace period start time.

14. The method of providing a grace period of claim 13, in which the grace period start time initiates the start of a grace period.

15. The method of providing a grace period of claim 14, further comprising determining a grace period duration for a media file being played from a license associated with the media file being played, and including grace.

16. The method of providing a grace period of claim 14, further comprising playing the media file no longer than the grace period.

17. The method of providing a grace period of claim 13, in which checking to determine that a clock of the CE device is currently reset further comprises saving a current time as a last known good time if the CE device is not reset.

18. The method of providing a grace period of claim 17, further comprising entering a normal mode of operation after saving a current time as a last known good time if the CE device is not reset.

19. The method of providing a grace period of claim 13, in which checking to determine that the clock of the CE device has ever been set further comprises entering an unset mode of operation if the clock has never been set.

20. The method of providing a grace period of claim 13, in which determining that the CE device is currently in a grace period further comprises continuing in a grace period mode if the CE device is currently in the grace period mode.