Digital signing authority dependent platform secret

• US 8,924,737 B2
• Filed: 08/25/2011
• Issued: 12/30/2014
• Est. Priority Date: 08/25/2011
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Thom, Stefan, Spiger, Robert Karl, Nystrm, Magnus Bo Gustaf, Wooten, David R.
• Primary Examiner(s): POWERS, WILLIAM S
• Application Number:
  US13/218,029
• Publication Number:
  US 20130054946A1
• Time in Patent Office: 1,223 Days
• Field of Search: 713187-189
• US Class Current: 713/187
• CPC Class Codes: G06F 21/575 Secure boot
• CPC Class Codes: G06F 21/602 Providing cryptographic facilities or services
• CPC Class Codes: G06F 21/73 by creating or determining hardware identification, e.g. serial numbers

Abstract

In accordance with one or more aspects, a representation of a configuration of a firmware environment of a device is generated. A secret of the device is obtained, and a platform secret is generated based on both the firmware environment configuration representation and the secret of the device. One or more keys can be generated based on the platform secret.

Claims

1. A method comprising:

generating, in a device, a representation of a configuration of a firmware environment of the device;

obtaining a secret of the device; and

generating, based on both the firmware environment configuration representation and the secret of the device, a platform secret such that a same platform secret is generated for firmware environments having different versions of a firmware component.

2. A method as recited in claim 1, the firmware environment configuration representation including a list of authorities identifying one or more authorities that digitally signed firmware components that were loaded on the device regardless of which firmware components those one or more authorities digitally signed and regardless of how many firmware components those one or more authorities digitally signed.

3. A method as recited in claim 1, the firmware environment configuration representation including an identification of one or more authorities that are permitted to modify a list of acceptable authorities that can digitally sign firmware components loaded on the device.

4. A method as recited in claim 1, the firmware environment configuration representation including a list of one or more authorities that digitally signed firmware components that were loaded on the device, and including at an identified place of the list of authorities an identifier of an authority that digitally signed an operating system loader loaded on the device.

5. A method as recited in claim 1, the firmware environment configuration representation including a list of authorities identifying one or more authorities that are permitted, based on a policy of the device, to have particular firmware components that are digitally signed by the one or more authorities loaded on the device regardless of whether the particular firmware components were loaded on the device.

6. A method as recited in claim 1, the firmware environment configuration representation including identifiers of authorities that are not permitted to verify a firmware component.

7. A method as recited in claim 1, the firmware environment configuration representation including identifiers of particular firmware components that are not permitted to be loaded.

8. A method as recited in claim 1, the generating the platform secret comprising using the firmware environment configuration representation and the secret of the device as inputs to a key derivation function, and using the output of the key derivation function as the platform secret.

9. A method as recited in claim 1, the generating the platform secret further comprising generating the platform secret based at least in part on an enterprise value that distinguishes the environment in which the device is located from other environments.

10. A method as recited in claim 1, the secret of the device being encoded in multiple fuses of a processor of the device.

11. A computing device comprising:

one or more processors; and

one or more computer storage media having stored thereon multiple instructions that, when executed by the one or more processors, cause the one or more processors to;

obtain, in the computing device, a platform secret generated based at least in part on both a secret of the computing device and a representation of a configuration of a firmware environment of the computing device, the platform secret being usable by an operating system loader of the computing device to generate one or more keys before executing an operating system kernel; and

generate, based on the platform secret, one or more keys.

12. A computing device as recited in claim 11, the multiple instructions further causing the one or more processors to regenerate, based on the platform secret, the one or more keys on subsequent boots of the computing device rather than persisting the one or more keys across boots.

13. A computing device as recited in claim 11, the multiple instructions further causing the one or more processors to use the platform secret as an authorization value to unlock another key.

14. A computing device as recited in claim 11, the one or more keys comprising a public/private key pair, the instructions further causing the one or more processors to:

generate a volume key used to encrypt data on a storage volume of the computing device;

encrypt the volume key with a private key of the public/private key pair;

store the encrypted volume key;

delete the private key of the public/private key pair; and

delete the platform secret.

15. A computing device as recited in claim 11, the firmware environment configuration representation including a list of authorities identifying one or more authorities that digitally signed firmware components that were loaded on the computing device regardless of which firmware components those one or more authorities digitally signed and regardless of how many firmware components those one or more authorities digitally signed.

16. A computing device as recited in claim 11, the firmware environment configuration representation including a list of authorities identifying one or more authorities that digitally signed firmware components that were loaded on the computing device in the order in which the firmware components were loaded on the computing device.

17. A computing device as recited in claim 11, the firmware environment configuration representation including identifiers of authorities that are not permitted to verify a firmware component.

18. A computing device as recited in claim 11, the firmware environment configuration representation including identifiers of particular firmware components that are not permitted to be loaded.

19. A computing device as recited in claim 11, the platform secret further generated based at least in part on an enterprise value that distinguishes the environment in which the computing device is located from other environments.

20. A method comprising:

generating, in a device, a list of authorities that digitally signed firmware components loaded on the device, the list of authorities identifying one or more authorities that digitally signed firmware components that were loaded on the device regardless of which firmware components those one or more authorities digitally signed and regardless of how many firmware components those one or more authorities digitally signed;

obtaining a secret of the device;

generating, by applying a key derivation function to a combination of both the list of authorities and the secret of the device, a platform secret specific to a particular operating system resulting in different platform secrets being generated for different operating systems despite at least some of the firmware components of the different operating systems being the same; and

generating, based on the platform secret, one or more volume keys used to encrypt data on a storage volume of the device.