Saving ECC keys to persistent memory with psa_crypto (or alternative method)

[Jsallende]

Hi to all!

I am trying to use the nrf5340 as a MCU for a IoT project. I need to create a ECC key using secp256r1 and save it in the nrf5340 for later use.

I am using the psa_crypto and giving it the attribute PSA_KEY_LIFETIME_PERSISTENT for it to be usable after a reboot. However trying to access the key with psa_export_public_key using the ID after a reboot, it fails saying PSA_ERROR_INVALID_HANDLE while it doesn't fail if I do it without rebooting. I am not calling psa_destroy_key so it should still be there.

My questions are:

Is this the way of safely storing an ECC key for later use in the nrf5340?

Why is it failing to export the public key after reboot? psa_export_public_key states that the EXPORT attribute is not necessary for public keys.

Thanks in advance!!

[Sigurd Hellesvik]

Hi Jsallende,

Are you building for nrf5340dk_nrf5340_cpuapp or nrf5340dk_nrf5340_cpuapp_ns?

Regards,
Sigurd Hellesvik

[Jsallende]

Hi Sigurd,

nrf5340dk_nrf5340_cpuapp_ns

Regards,

[Sigurd Hellesvik]

Hi

Thank you for the specification. I will need some time to look into this, but I will give you an answer by the end of week.

Regards,
Sigurd Hellesvik

[Sigurd Hellesvik]

Hi again

I have not been able to figure this out myself either.
So I have contacted our developers to get insight into the PSA library, and will inform you as soon as I hear back from them, hopefully on Monday.

Regards,
Sigurd Hellesvik

[Sigurd Hellesvik]

Hi

You can recover the handle after a reboot using psa_open_key().

Does this solve your issue?

Regards,
Sigurd Hellesvik