Arm Mbed OS support forum

Hardware CCM decryption failure STM32H7

Hello everyone,

I am currently evaluating SSL with a local server and an STM32 device. I’m unable to figure out why the decryption fails with CCM as the cipher suite.

FYI: I am using MbedTLS v2.14.1.

I’m using x86 local server with STM32 device as a client.

Here is what happens-

  1. Software CCM implementation on the client:
    When I use the software implementation of the CCM. Handshake and decryption is successful. Therefore, I can stream the data from STM32 and read it on the local server.

  2. Hardware CCM implementation with MBEDTLS_CCM_ALT:
    I have used ccm_alt.c provided from STM32Cube v1.9.0. Here, the handshake is successful. But decrypting the message fails.

The errors are:

ssl_decrypt_buf() returned -29056 (-0x7180)
mbedtls_ssl_read_record() returned -29056 (-0x7180)

Checks performed:
Same certificates are used for SW and HW implementations.
CCM self test returns ‘0’ for both HW and SW CCM implementations.
I have reserved enough heap, no memory issues.

Please find all the necessary data in the link provided. I have added the logs from the server and the client. I have added the certificates and the code files as well.

It would be of great help if somebody could point at what might be going wrong.

Thank you!

Best regards,