Which portions of the operating system typically do not make up the Trusted Computing Base?

The Trusted Computing Base (TCB) comprises the components of a system that enforce security policies, ensuring that the system operates in a secure manner. It is crucial for maintaining the integrity and confidentiality of sensitive data. Kernels, being the core component of the operating system, are fundamentally a part of the TCB because they manage resource access, enforce security policies, and act as an interface between hardware and software.

In contrast, the portions of the operating system listed in the other choices—such as file protection, user protection, and memory protection—do pertain to security measures but do not inherently form the core of the TCB. While these elements contribute to the overall security posture of the system, they rely on the underlying kernel and other components of the TCB to function effectively. Essentially, file protection ensures data is stored securely, user protection manages user account access and privileges, and memory protection prevents unauthorized access to memory areas, but they do not function independently as the foundational security elements that comprise the Trusted Computing Base.