ESP32 as Secure Bootloader for STM32

[aygh4266]

Hello Everyone,

I would like to get some Ideas, how can I use the ESP32 as Secure bootloader for STM32.

Background:ESP32 and STM32 communicate over UART. The ESP32 gets a Firmware Image via Bluetooth and store it in SPIFFS.
Before forwarding the image to the STM32, the signatured image should be verficated (signature verification) (on the esp32 side)

Once it has been verificated, it will be forwarded over UART.

Signing the image will be on PC so the image will be sent signed over Bluetooth.

Any Ideas will be appreciated ?

P.S. The STM32 own Secure Bootloader won't be used for some reasons.

[MicroController]

Once it has been verified, it will be forwarded over UART.

Anyone with physical access to the circuit can intercept/modify/replace the firmware on its way from the ESP32 to the STM32...