Compute/Verify truncated MAC using AES-128 CMAC calculation with PSA API

RE: Compute/Verify truncated MAC using AES-128 CMAC calculation with PSA API

SwRa — Fri, 18 Jul 2025 13:07:58 GMT

No problem. I will then close the case.

Regards,

Swathy

RE: Compute/Verify truncated MAC using AES-128 CMAC calculation with PSA API

GeneralPurpose — Fri, 18 Jul 2025 11:06:33 GMT

Ahaaa! I found that but didn't understand the usage of that macro at first: So I put in my algorithm and length of MAC to be and get a algorithm back:

psa_algorithm trunc_algo = PSA_ALG_TRUNCATED_MAC(PSA_ALG_CMAC, 5u);

With that new trunc_algo as my keys attribute I import my key and just use it for signing/verification with the new algorithm, like the original PSA_ALG_CMAC.

The example I wrote works correctly with that, thanks for your help!

Stephan

RE: Compute/Verify truncated MAC using AES-128 CMAC calculation with PSA API

SwRa — Fri, 18 Jul 2025 09:22:40 GMT

Hi Stephen,

I believe you can use this: https://arm-software.github.io/psa-api/crypto/1.2/api/ops/macs.html#c.PSA_ALG_TRUNCATED_MAC

Regards,

Swathy