difference between nrf_crypto_aes_crypt and nrf_crypto_aes_finalize

[Vinayak_dev]

Hello all,

I am working on nrf52832 and i need to use the nrf_crypto librariy. The example uses nrf_crypto_aes_crypt and nrf_crypto_aes_finalize function. Although they have the same end result, i am not able to understand the differences in the two function. can someone please clarify?

Regards,

Vinayak

[Håkon Alseth]

Hi,

 

when you're encrypting a data set, you use nrf_crypto_aes_crypt(), then at the last chunk, you use _finalize() to add any potential padding etc.

Its explained a bit better in the header file: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/group__nrf__crypto__aes.html#ga91db15150a3c0bd3ac45cd461ee4f250

 

Kind regards,

Håkon

[Vinayak_dev]

Thanks for the response. The example uses a message size of 64, but they either only call aes_crypt or aes_finalize to encrypt/decrypt the full message at once, both giving the same output. So its still not clear to me how the two functions differ. 

[Håkon Alseth]

In this specific use-case they will not differ, as there is no padding needed. For others, it might be needed. Please follow the API recommendations and always use _finalize() to ensure that you do not end up in a scenario where it was required and not called.

Kind regards,

Håkon