Hello everyone, I am working with the STM32H7B3 MCU and evaluating the Secure Boot and Secure Firmware Update (SBSFU) package. My setup uses a dual image slot configuration with the SECBOOT_ECCDSA_WITH_AES128_CBC_SHA256 cryptographic scheme. I would like to clarify several points regarding firmware loading, security settings, and debugging in both development and production phases.
Using USART, can we load sbsfu.bin or sbsfu.out with the system bootloader (BOOT0=1), and then program userapp.sfb via the secure bootloader (BOOT0=0)
Do we also need to program additional files such as a header bin?
If a header bin is required, how can we merge only sbsfu.bin and the header bin (excluding userapp.bin)?
For an STM32H7B3 device configured with RDP level 2, is it still possible to update UserApp.sfb via USART in BOOT0=0?
Can SFU_SECURE_USER_PROTECT_ENABLE (from app_sfu.h) be enabled/disabled during development? What about outside development mode? Is it possible to reprogram using USART or SWD ?
During development and production, I would like to:
Disable all security IPs (configured in app_sfu.h)
Load sbsfu_userapp.bin.
After production, enable all protections via the system bootloader (BOOT0=1) over USART, then power-cycle the board to reflect the protections.
Is this workflow possible?
Can option bytes/protections (e.g., PCROP, secure user area) be reset if RDP level 2 is not configured?
What is the role of nonce.bin and iv.bin?
What happens if they are missing?
Should they be identical or unique across different devices?
Is it possible to debug the UserApp with SBSFU (both with and without protections enabled)? If yes, could you suggest a simple method to debug using IAR Embedded Workbench IDE (EWARM)?
I plan to integrate ST X-CUBE-CLASSB functional safety tests and RAMECC monitoring into the UserApp. Could SBSFU configurations (such as MPU settings or other protections) interfere with these self-tests and potentially cause failures?
For context, please note that during the production phase, I will not have access to SWD/JTAG. All firmware programming/erasing and option byte configuration will be performed via USART using the system bootloader (BOOT0= 1).
