The method of protecting a secret key from being read by a non-secure software application, comprises a step (94) of recording the secret key as a routine stored in an executable-only memory. The routine having: load instructions to load the secret key into a memory readable by a secure and a non-secure software application, if the routine is called by the secure software application, and control instructions to leave only dummy data instead of the secret key in the readable memory if the software application calling the executable-only routine is the non-secure software application.