Replay protection nonce generation

1. A memory device for replay protection nonce generation, the memory device comprising:

a hash engine to produce a hash from a first input, the hash having a first length; and

processing circuitry to:

extract a first subset of the hash as a selector;

select a second subset of the hash using the selector, the second subset having a second length less than the first length; and

transmit the second subset as a nonce for a freshness value in a replay protected communication.

2. The memory device of claim 1 , wherein the first subset has a third length that is based on the first length and the second length.

3. The memory device of claim 2 , wherein the third length is equal to a number of bits to represent the first length divided by the second length.

4. The memory device of claim 3 , wherein the hash is divided into non-overlapping groups that have a length equal to the second length.

5. The memory device of claim 4 , wherein, to select the second subset of the hash using the selector, the processing circuitry is configured to:

evaluate a numerical value of bits in the selector; and

use a group in the non-overlapping groups that corresponds to the numerical value as the second subset.

6. The memory device of claim 1 , wherein the processing circuitry is configured to initialize a nonce sequence, wherein the nonce is used as the first nonce, and wherein a seed is selected as the first input.

7. The memory device of claim 6 , wherein, to select the seed, the processing circuitry is configured to:

receive, from a partner in the replay protected communication, a command that specifies a mode;

use the mode to update a multiplexer, the multiplexer having an input for each type of seed that is supported; and

produce the seed via the multiplexer.

8. The memory device of claim 6 , wherein the processing circuitry is configured to create a second nonce, following the first nonce, in the nonce sequence, wherein the hash of the first nonce is used as the first input to the second nonce.

9. A method for replay protection nonce generation, the method comprising:

producing a hash from a first input, the hash having a first length;

extracting a first subset of the hash as a selector;

selecting a second subset of the hash using the selector, the second subset having a second length less than the first length; and

transmitting the second subset as a nonce for a freshness value in a replay protected communication.

10. The method of claim 9 , wherein the first subset has a third length that is based on the first length and the second length.

11. The method of claim 10 , wherein the third length is equal to a number of bits to represent the first length divided by the second length.

12. The method of claim 11 , wherein the hash is divided into non-overlapping groups that have a length equal to the second length.

13. The method of claim 12 , wherein selecting the second subset of the hash using the selector includes:

evaluating a numerical value of bits in the selector; and

using a group in the non-overlapping groups that corresponds to the numerical value as the second subset.

14. The method of claim 9 , comprising initializing a nonce sequence, including the nonce as the first nonce, by selecting a seed as the first input.

15. The method of claim 14 , wherein selecting the seed includes:

receiving, from a partner in the replay protected communication, a command that specifies a mode;

using the mode to update a multiplexer, the multiplexer having an input for each type of seed that is supported; and

producing the seed via the multiplexer.

16. The method of claim 14 , comprising creating a second nonce, following the first nonce, in the nonce sequence by using the hash of the first nonce as the first input to the second nonce.

17. A machine readable medium including instructions for replay protection nonce generation, the instructions, when executed by processing circuitry, cause the processing circuitry to perform operations comprising:

producing a hash from a first input, the hash having a first length;

extracting a first subset of the hash as a selector;

selecting a second subset of the hash using the selector, the second subset having a second length less than the first length; and

transmitting the second subset as a nonce for a freshness value in a replay protected communication.

18. The machine readable medium of claim 17 , wherein the first subset has a third length that is based on the first length and the second length.

19. The machine readable medium of claim 18 , wherein the third length is equal to a number of bits to represent the first length divided by the second length.

20. The machine readable medium of claim 19 , wherein the hash is divided into non-overlapping groups that have a length equal to the second length.

21. The machine readable medium of claim 20 , wherein selecting the second subset of the hash using the selector includes:

evaluating a numerical value of bits in the selector; and

using a group in the non-overlapping groups that corresponds to the numerical value as the second subset.

22. The machine readable medium of claim 17 , wherein the instructions comprise initializing a nonce sequence, including the nonce as the first nonce, by selecting a seed as the first input.

23. The machine readable medium of claim 22 , wherein selecting the seed includes:

receiving, from a partner in the replay protected communication, a command that specifies a mode;

using the mode to update a multiplexer, the multiplexer having an input for each type of seed that is supported; and

producing the seed via the multiplexer.

24. The machine readable medium of claim 22 , wherein the instructions comprise creating a second nonce, following the first nonce, in the nonce sequence by using the hash of the first nonce as the first input to the second nonce.