Welcome @kostas_nomikos, to the community!
A Trusted Execution Environment is realised in Cortex-M by a technology called TrustZone developed by ARM, which can be found in the Cortex-M33, for example. However, you would not get any security if you subsequently realised something like this in a Cortex-M4 or Cortex-M7: an attacker could easily connect between your MCU and the TEE emulating module, which can be considered compromised from the outset.
The only option is to switch to new hardware with TrustZone, e.g. Cortex-M33 - e.g. STM32U5.
Hope that answers your question?
Regards
/Peter
In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
