HSE_KF_ACCESS_DEBUG_PROT attribute actual intention

[ale_di_vi]

Hello,

In our company we are working on a project having MWCT2015S microcontroller.

We store keys in the HSE_B secure memory setting the HSE_KF_ACCESS_DEBUG_PROT attribute so that the keys cannot be accessed (i.e. used) when a debugger is connected. Some of the keys may need to be updated once the product is in field (vehicle usage).

The question is: what does the sentence "cannot be used" include? Does it refer only to prevent keys usage for cryptographic operations OR it means that they cannot completely handled when a debugger is connected?

So, is it possible to update debug protected keys when the debugger is connected?

Thank you in advance and best regards,

Alessandro Di Vincenzo

[lukaszadrapa · Accepted solution]

Hi @ale_di_vi 

here is an explanation from SHE specification:

lukaszadrapa_0-1730467558420.png

Regards,

Lukas

[ale_di_vi]

Hi Lukas,
We don't store the key in its SHE-format. Can I consider this statement valid also for the non-SHE keys managed according to table 31 in chapter 7.1.4.2 from the HSE_B RM?
Thank you in advance,
Alessandro

[lukaszadrapa]

It looks like you have older version of the manual. I recommend to download the latest one which is version 2.3.

It's the same for non-SHE keys. If you are importing a key first time (i.e. to empty slot), it can be loaded in plain. However, if you are updating a key, it is mandatory to use encryption and/or authentication (Table 47 and 48 in RM v2.3). So, this is also trusted operation as described in the SHE, there's no difference.

Regards,
Lukas

[ale_di_vi]

Ok, got it: debug protection flag is not a problem for key update.
Thank you Lukas