Hierarchical trusted code for content protection in computers

• US 6,775,779 B1
• Filed: 04/06/1999
• Issued: 08/10/2004
• Est. Priority Date: 04/06/1999
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: England, Paul, Lampson, Butler W.
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): REVAK, CHRISTOPHER A
• Application Number:
  US09/287,698
• Time in Patent Office: 1,953 Days
• Field of Search: 713/167, 713/176, 713/200, 713/201, 713/202, 713/175, 713/189, 713/193, 713/194, 705/51-54, 705/77-79, 711/100, 711/154, 711/163
• US Class Current: 726/26
• 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: G06Q 10/10 Office automation; Time management

Abstract

An architecture for protecting premium content in a nonsecure computer environment executes only a small number of code modules in a secure memory. The modules are arranged in a hierarchy of trust, where a module names other modules that it is willing to trust, and those modules in turn name other modules that they are willing to trust. A secure loader loads a security manager that oversees a number of content-providing modules for manipulating the content. A memory manager assigns permissions to various pages of the secure memory. The memory has rings of different security. The security model can be extended to program modules and other devices on the computer'"'"'s bus, such as DMA controllers and peripherals.

Claims

1. A system for handling digital content in a secure manner, comprising:

a first module trusted by a content distributor for handling the digital content;

at least one other module specified by the first module as trusted for handling the digital content;

a secure memory for holding code and secret data for executing the modules, where the secure memory is divided into multiple pages; and

a table for storing a number of permissions for the modules for each of the pages.

2. The system of claim 1 further comprising at least one additional module specified by the at least one other module as trusted for handling the digital content.

3. The system of claim 2 where the at least one other module is a security manager.

4. The system of claim 2 where the additional module includes an application program that also includes a component specified as trusted for handling the digital content.

5. The system of claim 1 where the at least one other module is a content provider.

6. The system of claim 5 where the content provider is an application program for presenting the digital content to a user.

7. The system of claim 6 where the application program includes a component specified as trusted for handling the digital content.

8. The system of claim 1 further comprising a plurality of other modules specified by the first module as trusted to handle the digital content.

9. The system of claim 1 where the at least one other module is a hardware device.

10. The system of claim 9 where the hardware device has an identity, and where the first module verifies the identity of the hardware device.

11. The system of claim 9 where the first module grants access to a designated memory area to the hardware device.

12. The system of claim 1 further comprising a secure memory for holding code and secret data for executing the modules.

13. The system of claim 1 where the secure memory is divided into multiple pages.

14. The system of claim 1 where the secure memory is divided into a plurality of rings.

15. The system of claim 1 further comprising a processor for executing the modules.

16. The system of claim 1 further comprising a secure memory.

17. The system of claim 16 further comprising a secure loader that executes in the secure memory.

18. The system of claim 16 further comprising a security manager that decrypts premium data comprising the digital content.

19. The system of claim 1, the secure memory including pages set for use by the at least one other module, wherein the at least one other module is configured to execute from the secure memory.

20. The system of claim 1 further comprising at least one additional module specified by the at least one other module as trusted for handling the digital content.

21. The system of claim 1 is further comprising a security manager module.

22. The system of claim 1 where the at least one other module is a content provider.

23. The system of claim 1 where the at least one other module is a content provider comprising an application program for presenting the digital content to a user.

24. The system of claim 1 where the at least one other module is a content provider comprising an application program for presenting the digital content to a user and the application program includes a component specified as trusted for handling the digital content.

25. The system of claim 1 further comprising a plurality of other modules specified by the first module as trusted to handle the digital content.

26. The system of claim 1 wherein the at least one other module comprises software.

27. The system of claim 1 wherein the at least one other module comprises hardware.

28. A system for handling digital content in a secure manner, comprising:

a first module trusted by a content distributor for handling the digital content;

at least one other module specified by the first module as trusted for handling the digital content;

a secure memory for holding code and secret data for executing the modules, where the secure memory is divided into multiple pages and where the memory is divided into a plurality of rings; and

a table for storing a number of permissions for the modules for each of the pages.

29. A system for handling digital content in a secure manner, comprising:

a secure loader for manipulating secret data;

a security manager named by the secure loader as trusted for handling secret premium data comprising the digital content;

a number of content providers named by the security manager as trusted for performing operations upon the premium data;

a secure memory, where the security manager specifies at least one entry point for multiple code modules executing in the secure memory.

30. The system of claim 29 where the secure loader executes in the secure memory.

31. The system of claim 29 where the security manager decrypts premium data comprising the secret data.

32. The system of claim 29 where the secure loader programs permissions for code modules operating in the secure memory.

33. The system of claim 29 further comprising a memory manager for holding permissions for multiple pages in the secure memory.

34. The system of claim 33 where the permissions for each page include a permission for executing code located in that page.

35. A system for handling digital content in a secure manner, comprising:

a secure loader for manipulating secret data;

a security manager named by the secure loader as trusted for handling secret premium data comprising the digital content;

a number of content providers named by the security manager as trusted for performing operations upon the premium data; and

a secure memory, where the secure loader programs permissions for other code modules operating in the secure memory.

36. A system for handling digital content in a secure manner, comprising:

a secure loader for manipulating secret data;

a security manager named by the secure loader as trusted for handling secret premium data comprising the digital content;

a number of content providers named by the security manager as trusted for performing operations upon the premium data; and

a secure memory, and further comprising a memory manager for holding permissions for multiple pages in the secure memory.

37. The system of claim 36 where the permissions for each page include a permission for executing code located in that page.

38. A method implemented on a programmed digital computer for handling premium content, comprising:

executing a first code module;

calling a second code module from the first module;

determining that the second module is a trusted module;

setting pages in a secure memory for the use of the second module;

executing the second module from the secure memory.

39. The method of claim 38 where determining that the second module is trusted comprises determining that a previously trusted code module names the second module as trusted.

40. The method of claim 39 further comprising verifying a signature of the second module.

41. The method of claim 38, wherein the first and second modules execute from different security rings in the secure memory.

42. The method of claim 38, wherein the first module executes from a non-secure memory.

43. A method implemented on a programmed digital computer for handling premium content, comprising:

executing a first code module;

calling a second code module from the first module;

determining that the second module is a trusted module, where determining that the second module is trusted comprises determining that a previously trusted code module names the second module as trusted;

setting pages in a secure memory for the use of the second module;

executing the second module from the secure memory;

initiating a trusted interrupt handler for trapping interrupts during execution of the second module.

44. The method of claim 43 further comprising verifying a signature of the second module.

45. A method implemented on a programmed digital computer for handling premium content, comprising:

starting a secure loader in the digital computer;

initiating a secure session with the secure loader;

receiving a trusted security manager during the secure session;

storing the security manager to a nonvolatile storage;

thereafter, handling the premium content with the security manager;

storing the security manager in a secure memory, where handling the premium content comprises;

calling a code module for handling the premium content via an entry point in the security manager;

determining that the code module is named in the security manager as a trusted module;

designating one or more pages in the secure memory for the code module;

executing the code module from the designated pages.

46. The method of claim 45 where the secure loader issues a certificate attesting its authenticity during the session.

47. The method of claim 46, wherein receiving comprises receiving, from another party, the trusted security manager, where the other party determines whether or not to trust the secure loader based upon the certificate.

48. The method of claim 45 where the security manager is received in encrypted form.

49. The method of claim 48 where the secure loader decrypts the security manager.

50. The method of claim 45 further comprising storing the security manager in a secure memory.

51. A medium bearing instructions and data for performing a method for handling premium content, the method comprising:

executing a first code module;

calling a second code module from the first module;

determining that the second module is a trusted module;

setting pages in a secure memory for the use of the second module;

executing the second module from the secure memory.

52. The medium of claim 51, wherein the first and second modules execute from different security rings in the secure memory.

53. The medium of claim 51, wherein the first module executes from a non-secure memory.

54. The medium of claim 51 further comprising at least one additional module trusted for handling digital content.

55. The medium of claim 54, wherein the at least one additional module is a security manager.

56. The medium of claim 54, wherein the at least one additional module is a content provider.

57. The medium of claim 56, wherein the content provider is an application program for presenting the premium content to a user.

58. The medium of claim 57, wherein the application program includes a component specified as trusted for handling the premium content.

59. The medium of claim 51, further comprising a plurality of other modules specified by the first module as trusted to handle the premium content.