Method for switching between virtualized and non-virtualized system operation

A computer program comprising computer-readable code which when executed on an embedded system capable of operating as a virtualized system under supervision of a hypervisor or as a non-virtualized system under supervision of an operating system causes the embedded system to:

• be executed in a normal mode, if no execution of a security critical function is required by the embedded system, where the normal mode execution is performed under supervision of the operating system;
• be executed in a protected mode by instructing the operating system to switch from execution of the embedded system in normal mode to execution in protected mode, by switching the execution of the embedded system from the operating system to a hypervisor, if execution of a security critical function is required by the embedded system, where protected mode execution is performed under supervision of the hypervisor, and
• return to execution in normal mode, by switching, under supervision of the hypervisor, the embedded system from protected mode to normal mode, when execution of said security critical function is no longer required by the embedded system, wherein
• the computer program further comprises computer-readable code which when executed on the embedded system causes a transition cryptographic module to decrypt and verify, on the basis of at least one chip unique secret key, integrity of code associated with the hypervisor, the security critical function, and associated data, if the mode state of the mode state register is set to protected mode, while access to any chip unique secret key is prohibited if the mode state of the mode state register is set to normal mode.