How to access functions like SHA-256 from the CRYPTOCELL?

RE: How to access functions like SHA-256 from the CRYPTOCELL?

Frank Aune — Fri, 28 Jun 2024 22:56:21 GMT

Check out latest CC312 doc for nRF5340 here: https://docs.nordicsemi.com/bundle/ps_nrf5340/page/cryptocell.html#cc_frontpage

Bare-metal library from trustedfirmware.org: https://git.trustedfirmware.org/TF-M/trusted-firmware-m/+/refs/heads/main/platform/ext/accelerator/cc312/cc312-rom

Nordics libs are more integrated and tested together with rest of NCS, but the above give you more control at the expense of being exposed to bare-metal.

RE: How to access functions like SHA-256 from the CRYPTOCELL?

Torsten Robitzki — Thu, 16 May 2024 11:35:26 GMT

Well, using Zephyr is promising to make it at least a little bit easier to run the same code on different hardware.

RE: How to access functions like SHA-256 from the CRYPTOCELL?

Hieu — Thu, 16 May 2024 11:30:52 GMT

Hi Torsten,

I am not sure which kind of portability you are looking for. Most of the code in nRF Connect SDK (NCS) is specific to NCS or Zephyr at certain depth.

What I can say is that the nRF Security library follows the PSA Certified Crypto API. So, the code should be portable to any system/environment that is also compliant with PSA Certified Crypto API.

Best regards,

Hieu

RE: How to access functions like SHA-256 from the CRYPTOCELL?

Torsten Robitzki — Thu, 16 May 2024 05:47:24 GMT

Hi Hieu

thank you for your fast reply. Using the Mbed library for Zephyr is not really intuitive ;-) This also means, that this is not going to be portable, right? (which is not really a concern for us, just out of curiosity)

best regards

Torsten

RE: How to access functions like SHA-256 from the CRYPTOCELL?

Hieu — Wed, 15 May 2024 17:43:59 GMT

Hi Torsten,

I am sorry to hear you were confused. I will relay your experience to our teams to improve the experience.

In newer versions of the nRF Connect SDK, we recommend using the nRF Security library for cryptography purposes. Its documentation is here:
nRF Security — nRF Connect SDK 2.6.1 documentation (nordicsemi.com).

You can find samples here: Cryptography samples — nRF Connect SDK 2.6.1 documentation (nordicsemi.com).

By default, the library will use the hardware CryptoCell as a backend where possible, and software libraries otherwise.
For example, with AES encryption, 128-bit operations will be handled by the CryptoCell, but 256-bit operations will be done by a software library like nrf_oberon, because the CryptoCell doesn't support that.

I hope this clears things up a little. Please give those resources I linked a try and let me know if anything is still confusing.

Hieu