The VMS scheme discussed in the preceding problem is often referred to as a ring protection structure, as illustrated in Figure. Indeed, the simple kernel/user scheme, as described in Section 3.3, is a two-ring structure. A potential disadvantage of this protection structure is that it cannot readily be used to enforce a €œneed-to-know€

Principle. [SILB04] gives this example: If an object is accessible in domain Dj but not in domain Di, then j Explain clearly what the problem is that is referred to in the preceding paragraph.

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