CLOCK ROLL FORWARD DETECTION

• US 20090287942A1
• Filed: 05/13/2008
• Published: 11/19/2009
• Est. Priority Date: 05/13/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Farrugia, Augustin J., Sullivan, Nicholas, Betouin, Pierre
• Granted Patent: US 8,769,675 B2
• Time in Patent Office: Days
• US Class Current: 713/194
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock
• CPC Class Codes: G06F 21/10 Protecting distributed programs or content, e.g. vending or licensing of copyrighted material protection in video systems or pay television H04N7/16 ; Digital rights management [DRM]
• CPC Class Codes: G06F 21/57 Certifying or maintaining trusted computer platforms, e.g. secure boots or power-downs, version controls, system software checks, secure updates or assessing vulnerabilities
• 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
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/0084 wherein the usage restriction can be expressed as a specific time or date

Abstract

Method and apparatus to detect clock roll-forward attacks in a computing device or similar system. This protects against hackers who tamper with the system clock of, for instance, a digital media playback device in order to access a content item which has been rented for a limited time. By detecting clock roll-forward tampering, the present method and system prevent such hackers from accessing the content item outside its authorized rental time period.

Claims

1. A method for detecting tampering with timing in a system, wherein the system stores a plurality of files, comprising the acts of:

storing for each file a time;

storing for each file a content identification value;

subsequently accessing for each file the stored content identification value and the stored time;

determining for each file if its stored time is equal to or more recent than a current time, and otherwise indicating tampering;

and if the stored time is equal to the current time, determining for the file if the stored content identification value is the same as a current content identification value for the file and otherwise indicating tampering; and

allowing access to a content item if there is no indication of tampering.

2. The method of claim 1, further comprising, if there is no indication of tampering, storing a new current time for each file.

3. The method of claim 1, wherein the act of allowing access includes providing at least one key for decrypting the content item.

4. The method of claim 1, wherein the method is part of a Digital Rights Management system.

5. The method of claim 4, wherein the Digital Rights Management system sets a time period for access to the content item.

6. The method of claim 1, wherein the time is maintained by a clock associated with the system.

7. The method of claim 1, wherein the system is a computer, mobile telephone device, media playback device, or personal digital assistant.

8. The method of claim 1, wherein the system is not connected to a network during the method.

9. The method of claim 1, wherein the method detects a clock roll-forward attack on the system timing.

10. The method of claim 1, wherein the acts of storing store in a secure manner.

11. The method of claim 1, wherein the secure manner includes encryption.

12. The method of claim 1, wherein the acts of storing include arranging the time and content identification value for each file in a database.

13. The method of claim 1, wherein the content identification value is one of a digest or selected portions of the content of the file.

14. The method of claim 1, further comprising the acts of:

applying the method to all files in a directory.

15. The method of claim 1, further comprising the acts of:

applying the method only to selected files in a directory.

16. A computing device programmed to perform the method of claim 1.

17. A computer readable medium storing computer code for execution in a computing device to perform the method of claim 1.

18. A media playback apparatus comprising:

a playback mechanism;

a content storage storing a plurality of files and operatively coupled to the playback mechanism;

a system clock;

a second storage storing for each file a time as determined by the system clock and a content identification value;

a test logic operatively coupled to the system clock and to the file storage and which determines for each file identified in the second storage if its stored time is equal to or more recent than a current time from the system clock and otherwise indicating tampering;

and if the stored time is equal to the current time, determining for the file if the stored content identification value is the same as a current content identification value for the file and otherwise indicating tampering; and

allowing access to a content item in the content storage if there is no indication of tampering.

19. The apparatus of claim 18, wherein if there is no indication of tampering, the test logic stores in the second storage a new current time for each file.

20. The apparatus of claim 18, further comprising a key storage for storing keys for decrypting the content files, and wherein the test logic allows access by providing at least one of the stored keys.

21. The apparatus of claim 18, wherein the apparatus is a computer, mobile telephone device, media playback device or personal digital assistant.

22. The apparatus of claim 18, wherein the second storage is secure.

23. The apparatus of claim 22, wherein the data in the second storage is encrypted.

24. The apparatus of claim 18, wherein the second storage is arranged as a database.

25. The apparatus of claim 18, wherein the content indentification value is one of a digest or selected portions of the content of the file.