PROBABILISTIC KEY ROTATION

• US 20190007207A1
• Filed: 09/10/2018
• Published: 01/03/2019
• 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
• Granted Patent: US 10,382,200 B2
• Time in Patent Office: Days
• 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, comprising:

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

causing a device to perform the encryption operation using the first cryptographic key;

determining, based at least in part on a stochastic process, to cause a counter to be updated; and

based at least in part on the counter satisfying a set of key rotation criteria, causing the first cryptographic key to be replaced with a second cryptographic key, the set of key rotation criteria having a probability of being satisfied that is associated with a frequency of key rotation.

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

the device is a hardware security module of a plurality of hardware security modules with access to the first cryptographic key when the request is received; and

causing the first cryptographic key to be replaced causes each hardware security module of the plurality of hardware security modules to replace the first cryptographic key with the second cryptographic key.

3. The computer-implemented method of claim 1, wherein determining, based at least in part on the stochastic process, to cause the counter to be updated is based at least in part on an output of a random or pseudorandom value generator.

4. The computer-implemented method of claim 1, wherein determining, based at least in part on the stochastic process, to cause the counter to be updated:

generating a value based at least in part on the stochastic process; and

as a result of the value satisfying a counter update condition, incrementing the counter.

5. The computer-implemented method of claim 1, wherein causing the device to perform the encryption operation using the first cryptographic key includes causing the device to use a value generated according to the stochastic process as input into an encryption algorithm.

6. The computer-implemented method of claim 1, wherein the counter satisfying the set of key rotation criteria is based at least in part on the first cryptographic key being used to fulfill at least a threshold number of encryption operations.

7. A system, comprising:

one or more processors; and

memory storing instructions that, as a result of execution by the one or more processors, cause the system to;

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

cause a device to perform the encryption operation using the first cryptographic key;

determine, based at least in part on a stochastic process, to cause a counter to be updated; and

based at least in part on the counter satisfying a set of key rotation criteria, cause the first cryptographic key to be replaced with a second cryptographic key, the set of key rotation criteria having a probability of being satisfied that is associated with a frequency of key rotation.

8. The system of claim 7, wherein the instructions to determine to cause the counter to be updated include instructions that cause the system to:

obtain a stochastically-generated value;

supply the stochastically-generated value as an argument to a probabilistic process that has a known probability of producing a particular outcome; and

produce the particular outcome.

9. The system of claim 8, wherein the probabilistic process comprises determining whether the stochastically-generated value is an integer multiple of a second integer.

10. The system of claim 9, wherein a value of the second integer is selected such that a probability of the stochastically-generated value being the integer multiple of the second integer has a known probability distribution.

11. The system of claim 7, wherein:

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

the instructions that cause the counter to be updated include instructions to submit a second request, to another device of the system, to update the counter.

12. The system of claim 7, wherein instructions to determine to cause the counter to be updated include instructions that cause the system to compare a stochastically-generated value with a threshold value, wherein the threshold value is selected based at least in part on the set of key rotation criteria.

13. A computer-readable storage medium having stored thereon instructions that, as a result of execution by one or more processors of a system, cause the system to:

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

cause a device to perform the encryption operation using the first cryptographic key;

determine, based at least in part on a stochastic process, to cause a counter to be updated; and

based at least in part on the counter satisfying a set of key rotation criteria, cause the first cryptographic key to be replaced with a second cryptographic key, the set of key rotation criteria having a probability of being satisfied that is associated with a frequency of key rotation.

14. The computer-readable storage medium of claim 13, wherein the first cryptographic key is a cryptographic key of a plurality cryptographic keys managed by the system.

15. The computer-readable storage medium of claim 13, wherein the set of rotation criteria is determined based at least in part on a probability of the counter failing to update.

16. The computer-readable storage medium of claim 13, wherein:

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

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

17. The computer-readable storage medium of claim 13, wherein the stochastic process comprises making a non-deterministic determination whether to update the counter.

18. The computer-readable storage medium of claim 13, wherein the set of key rotation criteria comprises the counter exceeding a threshold value.

19. The computer-readable storage medium of claim 13, wherein the instructions to determine, based at least in part on the stochastic process, to cause the counter to be updated include instructions that cause the system to determine whether a stochastically generated value is divisible by another value.

20. The computer-readable storage medium of claim 13, wherein the instructions to determine, based at least in part on the stochastic process, to cause the counter to be updated include instructions that cause the system to determine whether a stochastically generated sequence of bits satisfies one or more conditions on the sequence.