System and Method for Authenticating an Operating System to a Central Processing Unit, Providing the CPU/OS with Secure Storage, and Authenticating the CPU/OS to a Third Party

• US 20070118769A1
• Filed: 12/22/2006
• Published: 05/24/2007
• Est. Priority Date: 10/26/1998
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: England, Paul, DeTreville, John, Lampson, Butler
• Granted Patent: US 7,415,620 B2
• Time in Patent Office: Days
• US Class Current: 713/193
• CPC Class Codes: G06F 21/1011 to devices
• CPC Class Codes: G06F 21/445 by mutual authentication, e.g. between devices or programs
• 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 21/575 Secure boot
• CPC Class Codes: G06F 2221/2103 Challenge-response
• CPC Class Codes: G06F 2221/2113 Multi-level security, e.g. mandatory access control
• CPC Class Codes: G06F 2221/2129 Authenticate client device independently of the user
• CPC Class Codes: G06F 9/4406 Loading of operating system
• CPC Class Codes: G06F 9/468 Specific access rights for resources, e.g. using capability register

Abstract

In accordance with certain aspects, a chain of trust is established between a subscriber unit and a content provider. A request is submitted from the subscriber unit to the content provider. A challenge nonce is generated at the content provider and returned to the subscriber unit. At the subscriber unit, an operating system (OS) certificate containing an identity of the operating system from the software identity register, information describing the operating system, the challenge nonce, and a CPU public key is formed, and the OS certificate is signed using a CPU private key. The OS certificate and a CPU manufacturer certificate supplied by a manufacturer of the CPU are passed from the subscriber unit to the content provider, and are evaluated at the content provider to determine whether to reject or fulfill the request.

Claims

1. A method for establishing a chain of trust between a subscriber unit and a content provider, the subscriber unit having a central processing unit (CPU) and an operating system (OS), the CPU having a pair of private and public keys, a manufacturer certificate supplied by a manufacturer of the CPU, and a software identity register that holds an identity of the operating system, the method comprising:

submitting a request from the subscriber unit to the content provider, the request specifying a particular content;

generating, at the content provider, a challenge nonce;

returning the challenge nonce from the content provider to the subscriber unit;

forming, at the subscriber unit, an OS certificate containing the identity from the software identity register, information describing the operating system, the challenge nonce, and the CPU public key and signing the OS certificate using the CPU private key;

passing the OS certificate and the CPU manufacturer certificate from the subscriber unit to the content provider; and

evaluating, at the content provider, the OS certificate and the CPU manufacturer at the content provider to determine whether to reject or fulfill the request.

2. The method as recited in claim 1, wherein forming an OS certificate comprises forming the OS certificate with one or more items from a boot log containing identities of software components that are executing on the CPU.

3. The method as recited in claim 1, wherein evaluating the OS certificate comprises determining whether to trust the identity in the OS certificate.

4. The method as recited in claim 1, wherein evaluating the OS certificate comprises determining whether the challenge nonce returned in the OS certificate is the challenge nonce generated by the content provider.

5. The method as recited in claim 1, wherein evaluating the OS certificate comprises verifying the signature on the OS certificate using the CPU public key contained in the OS certificate.

6. The method as recited in claim 1, wherein evaluating the OS certificate comprises determining whether the OS certificate and the manufacturer certificate contain an identical CPU public key.

7. The method as recited in claim 1, wherein evaluating the OS certificate comprises verifying a manufacturer signature on the manufacturer certificate.

8. The method as recited in claim 1, wherein evaluating the OS certificate comprises determining whether to trust the manufacture of the CPU.

9. The method as recited in claim 1, further comprising downloading the content specified in the request in an event that the content provider elects to fulfill the request.

10. The method as recited in claim 9, further comprising encrypting the content using a storage key derived in part from the identity of the operating system.

11. In a system having a subscriber unit and a content provider, in which the subscriber unit has a central processing unit (CPU) and an operating system (OS) and the CPU further includes a pair of private and public keys, a manufacturer certificate supplied by a manufacturer of the CPU, and a software identity register that holds an identity of the operating system, a computer program architecture stored on one or more computer-readable storage media resident at the subscriber unit and content provider for establishing a chain of trust between the subscriber unit and the content provider, the program comprising:

submitting a request from the subscriber unit to the content provider, the request specifying a particular content;

generating, at the content provider, a challenge nonce;

returning the challenge nonce from the content provider to the subscriber unit;

forming, at the subscriber unit, an OS certificate containing the identity from the software identity register, information describing the operating system, the challenge nonce, and the CPU public key and signing the OS certificate using the CPU private key;

passing the OS certificate and the CPU manufacturer certificate from the subscriber unit to the content provider; and

evaluating, at the content provider, the OS certificate and the CPU manufacturer at the content provider to determine whether to reject or fulfill the request.

12. A method for associating a level of trust with a user computer by a third party, the user computer having a central processing unit (CPU) and an operating system (OS), the CPU having a pair of private and public keys, a manufacturer certificate supplied by a manufacturer of the CPU, and a software identity register that holds an identity of an operating system executing on the CPU, the method comprising:

establishing a secure connection between the user computer and the third party;

generating, at the third party, a challenge nonce;

transmitting, by the third party, the challenge nonce to the user computer over the secure connection;

signing, by the user computer, an OS certificate and the challenge nonce using the CPU private key;

transmitting, by the user computer, the signed OS certificate and the signed challenge nonce to the third party over the secure connection; and

associating, by the third party, the level of trust for the user computer using the signed OS certificate.

13. The method as recited in claim 12, wherein the OS certificate comprises the software identity register.

14. The method as recited in claim 12, wherein the level of trust is based on the operating system identified by the software identity register.

15. The method as recited in claim 12, wherein the OS certificate comprises a boot log.

16. The method as recited in claim 12, wherein the OS certificate comprises a register containing a value associated with a boot log.

17. The method as recited in claim 12, wherein the OS certificate comprises identities of software components executing on the CPU.

18. The method as recited in claim 17, wherein the level of trust is based on the identities of the software components executing on the CPU.

19. The method as recited in claim 12, wherein the OS certificate comprises identities of device drivers executing on the CPU.

20. The method as recited in claim 19, wherein the level of trust is based on the identities of the device drivers executing on the CPU.

21. The method as recited in claim 12, further comprising:

submitting, by the user computer, a request to the third party for access to specific content;

evaluating, by the third party, whether to permit access based on the level of trust associated with the user computer.

22. The method as recited in claim 21, wherein the access comprises:

transmitting, from the third party, the specific content to the user computer through the secure connection.

23. The method as recited in claim 21, wherein the access comprises:

transmitting, from the third party, a storage key for the specific content to the user computer through the secure connection, wherein the specific content was previously stored on the user computer.

24. The method as recited in claim 23, wherein the specific content was obtained outside the secure connection.