AES hardware decryption

[Michal]

Hello. We are using nrf52840 for our product and I wanted to use aes ccm encryption for security. I was able to integrate CC310 library but I found out that encryption works fine but decryption returns CRYS_FATAL_ERROR (0x00F50000). I tried basic example and it fails the same way if I change mode to decrypt (examples/crypto/nrf_cc310/aes, main.c:90 ret = CRYS_AESCCM(SASI_AES_DECRYPT,). 

Regards

[Michal]

Turns out that valid MAC must be provided. Otherewise decryption fails with this not very descriptive error code. 

NORDIC: Consider creating error code for wrong MAC. Also it would be nice to mention MAC will be checked internally. My understanding was that MAC will be calculated over decrypted message and returned to user to compare with received one. Maybe that solution is obvious for people common with crypto but that wasnt me

[Jakub Rzeszutko]

Hi,

Did you try using nrf_crypto library? Such feedback shall be handled there.

infocenter.nordicsemi.com/.../lib_crypto.html

[Michal]

I used API of NRF_CC310 itself. But I checked nrf_crypto and it was returning NRF_ERROR_INTERNAL_ERROR which is not very helpful as well.