The trusted computing base (TCB) ensures security within a system when a process in one domain must access another domain in order to retrieve sensitive information. What function does the TCB initiate to ensure that this is done in a secure manner?

A.
I/O operational execution

B.
Process deactivation

C.
Execution domain switching

D.
Virtual memory to real memory mapping

Explanation:
C: Execution domain switching takes place when a CPU needs to move between executing instructions for a highly trusted process to a less trusted process or vice
versa. The trusted computing base (TCB) allows processes to switch domains in a secure manner in order to access different levels of information based on their
sensitivity. Execution domain switching takes place when a process needs to call upon a process in a higher protection ring. The CPU goes from executing instructions
in user mode to privileged mode and back.
A is incorrect because input/output (I/O) operations are not initiated to ensure security when a process in one domain must access another domain in order to retrieve
sensitive information. I/O operations include control of all input/output devices. I/O operations are functions within an operating system that allow input devices (such as
a mouse or keyboard) and output devices (such as a monitor or printer) to interact with applications and with itself.
B is incorrect because process deactivation takes place when a process’s instructions are completely executed by the CPU or when another process with a higher
priority calls upon the CPU. When a process is deactivated, the CPU’s registers must be filled with new information about the new requesting process. The data that is
getting switched in and out of the registers may be sensitive, so the TCB components must make sure this takes place securely.
D is incorrect because memory mapping takes place when a process needs its instructions and data processed by the CPU. The memory manager maps the logical
address to the physical address so that the CPU knows where the data is located. This is the responsibility of the operating system’s memory manager.