Probabilistic key rotation

• US 9,300,464 B1
• Filed: 06/20/2013
• Issued: 03/29/2016
• Est. Priority Date: 02/12/2013
• Status: Active Grant

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: Roth, Gregory Branchek
• Primary Examiner(s): Tabor, Amare F
• Application Number:
  US13/922,946
• Time in Patent Office: 1,013 Days
• Field of Search: 380/278
• US Class Current: 1/1
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying

Abstract

Information, such as a cryptographic key, is used repeatedly in the performance of operations, such as certain cryptographic operations. To prevent repeated use of the information from enabling security breaches, the information is rotated (replaced with other information). To avoid the resource costs of maintaining a counter on the number of operations performed, decisions of when to rotate the information are performed based at least in part on the output of stochastic processes.

Claims

1. A computer-implemented method for managing cryptographic keys in a distributed system, comprising:

under the control of one or more computer systems configured with executable instructions,

storing a first cryptographic key in each of a plurality of security modules;

receiving a request to perform an operation, the performance of which involves an encryption operation using the first cryptographic key specified in the request; and

as a result of receiving the request;

causing a selected security module from the plurality of security modules to perform the encryption operation using the first cryptographic key;

performing a stochastic process to generate a value; and

when the value satisfies a set of key rotation criteria that limit the probability of using the same nonce multiple times with the first cryptographic key, causing each security module of the plurality of security modules to replace the first cryptographic key with a second cryptographic key.

2. The computer-implemented method of claim 1, wherein:

the encryption operation includes stochastic generation of a nonce.

3. The computer-implemented method of claim 1, wherein the value is output of a random or pseudorandom value generator.

4. The computer-implemented method of claim 1, wherein:

the stochastic process comprises;

randomly or pseudorandomly generating an initial value; and

as a result of the generated initial value satisfying a set of counter update conditions, determining the value by updating a counter.

5. The computer-implemented method of claim 1, wherein causing the selected security module to perform the encryption operation using the first cryptographic key includes causing the selected security module to use the value when performing the encryption operation.

6. The computer-implemented method of claim 1, wherein the first cryptographic key is accessible to each security module of the plurality of security modules.

7. A computer-implemented method, comprising:

under the control of one or more computer systems configured with executable instructions,

as a result of a received request to perform an operation, the performance of which involves use of first information;

determining a stochastically generated value;

when the stochastically generated value satisfies a set of rotation criteria that limit the probability of using the same nonce multiple times with the first information, replacing the first information with second information; and

when the stochastically generated value fails to satisfy the set of rotation criteria, allowing the first information to be used to perform the operation at least one additional time in response to another request.

8. The computer-implemented method of claim 7, wherein the first information is a cryptographic key.

9. The computer-implemented method of claim 7, wherein the stochastically generated value is based at least in part on output of a random or pseudorandom number generator.

10. The computer-implemented method of claim 7, wherein the stochastically generated value is a probabilistically updated counter.

11. The computer-implemented method of claim 7, wherein the method further comprises:

receiving the request;

selecting, from a plurality of devices each with access to the first information and capable of performing the operation, a device to perform the operation; and

causing the selected device to perform the operation.

12. The computer-implemented method of claim 7, wherein the method further comprises causing the stochastically generated value to be used to perform the operation.

13. A system, comprising:

a plurality of computing devices that each store first information;

a request processing subsystem comprising a collection of computing resources collectively configured to;

process requests to perform operations involving the first information by at least, for each request of a plurality of the requests, selecting a computing device from the plurality of computing devices to use the first information as part of processing the request; and

generate rotation determinations probabilistically in a manner that limits use of the same nonce with the first information multiple times such that, as a result of a rotation determination indicating rotation, the plurality of computing devices use second information instead of the first information.

14. The system of claim 13, wherein:

the first information is a cryptographic key; and

the operations include cryptographic operations using the cryptographic key.

15. The system of claim 13, wherein probabilistically generating rotation determinations includes determining a random or pseudorandom value and checking whether the rotation determination satisfies one or more conditions.

16. The system of claim 13, wherein probabilistically generating rotation determinations includes probabilistically updating a counter that, when the counter satisfies one or more conditions, results in a rotation determination indicating rotation.

17. The system of claim 13, wherein at least a subset of the rotation determinations are each generated as a result of a corresponding received request to use the first information to perform a corresponding operation.

18. The system of claim 13, wherein:

the requests are web service requests that specify the first information by an identifier for the first information; and

upon replacement of the first information with the second information, the second information is specifiable to the system by the identifier for the first information.

19. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed by one or more processors of a system, cause the system to:

probabilistically generate rotation determinations in a manner that limits use of the same nonce with first information multiple times, each rotation determination indicating whether to replace the first information with second information when processing requests;

when a generated rotation determination is positive, cause the first information used in processing requests to be replaced with the second information; and

when a generated rotation determination is negative, allow the first information to be used for processing additional requests to be processed using the first information.

20. The non-transitory computer-readable storage medium of claim 19, wherein the first information is a first cryptographic key of a plurality cryptographic keys managed by the system.

21. The non-transitory computer-readable storage medium of claim 19, wherein each of at least a subset of the rotation determinations is generated as a result of a received request to perform an operation using the first information.

22. The non-transitory computer-readable storage medium of claim 19, wherein:

the first information is accessible to a plurality of devices of the system; and

causing the first information to be replaced with the second information includes causing the second information to become accessible to each device of the plurality of devices.

23. The non-transitory computer-readable storage medium of claim 19, wherein each rotation determination of at least a subset of the rotation determinations is based at least in part on one or more conditions and a randomly or pseudorandomly generated value.

24. The non-transitory computer-readable storage medium of claim 19, wherein:

probabilistically generating rotation determinations includes probabilistically determining whether to update a counter; and

each rotation determination of at least a subset of the rotation determinations is based at least in part on whether the counter has reached a threshold.

25. The non-transitory computer-readable storage medium of claim 19, wherein each probabilistically generated rotation determination of at least a subset of the probabilistically generated rotation determinations is based at least in part on a determination whether a stochastically generated value is divisible by another value.

26. The non-transitory computer-readable storage medium of claim 19, wherein each probabilistically generated rotation determination of at least a subset of the probabilistically generated rotation determinations is based at least in part on a determination whether a stochastically generated sequence of bits satisfies one or more conditions on the sequence.