Pull Request Overview

Depends on OxidosAutomotive:board_nucleo_u545re_q

This pull request adds support for the AES driver accelerator for the stm32u5xx chip series and it generalises the AES hil. Where previously it was, necessarily AES128, it now supports 256 bit keys. The size of the key is now a const generic of the type AES: AES and AES. Modified older code accordingly.

1. AES impementation for stm32u5xx

• Created three files, mod.rs, gcm_ccm.rs and registers.rs, containing the logic for the AES accelerator for 128 and 256 length keys, for the following modes: ECB, CBC, CTR, GCM, GMAC, CCM
• updated dma.rs and chip.rs with the necessary code to connect the peripheral to DMA. The addition is, essentially, a way to determine the data width for source and destination, and to determine the padding

2. AES 256-bit support

• modified the symmetric_encryption hil to allow for 256 bit keys, renamed constants accordingly
• modified the aes driver to be independent of the key size
• added three new testing files, aes256.rs (for ECB, CBC, CTR modes), aes_ccm_256.rs and aes_gcm_256.rs for 256 bit key testing. The vectors used in testing were taken from NIST
• modified old code to use AES instead of AES128

Testing Strategy

• Deployment: Deployment was performed using probe-rs and openocd.
• AES functionallity was tested by using the afformentioned test files and the existing test files for aes128: ECB, CBC, CTR, GCM, CCM.

Documentation Updated

• no updates are required.

Formatting

• Ran make prepush.

AI Use

AI was used for suggestions to create cleaner code, debugging, and help in the creation of test file as the code for testing is uniform and doesn't require interaction with the peripheral, just sending and checking values. All generated code, register offsets, and memory maps were manually verified against the STM32U545 Reference Manual and validated on live hardware.

• The PR description details my use of AI in the production of the
  code in this PR, if any, and I have manually checked and
  personally certify the entire contents of this PR.