Update user key without knowing MasterKey

[RedOne]

I see in all of functions that should change user keys by updating them or erasing them one parameter is mandatory - value of a MasterKey. My question is - is it possible to update userKey without using value of master key, only using a ID of the masterKey or somekind of pointer that goes to MasterKey in memory without exposing it in code?

If possible, could this be in Crypto mcal way?

[lukaszadrapa]

Hi Denis,

user key can be updated with a knowledge of MASTER_ECU_KEY or current KEY. But it is not necessary to expose the keys in flash / code. Typical approach is to calculate M1 - M5 values offline (using MASTER_ECU_KEY or current KEY) and then send the values M1-M5 somehow to the microcontroller.

Regards,

Lukas

[RedOne]

Is there an examples of this "somehow" method?

[lukaszadrapa]

When you are going to update the keys, such request usually comes from outside world - via CAN, LIN, UART... So, some master system should send M1-M5 values to the microcontroller. This is application dependent, I do not have such example.

Regards,

Lukas