Bell-Lapadula policy

The content below are related to the Bell-Lapadula policy.

a) What is the advantage of maintaining categories in addition to clearance levels?

b) Which of the following two statements is correct?

- For a user to get access to a document, it is sufficient that the user has access to at least one category to which the document belongs.

- For a user to get access to a document, it is necessary that the user has access to all the categories to which the document belongs.

c) Bell-Lapadula policy can be re-formulated with categories only (that is, without the clearance levels). In particular, consider an example where a document can have one of the four standard clearance levels (Top Secret, Secret, Confidential, Unclassified) and can belong to any of two categories A and B.

Introduce a new set of categories and the assignment of access rights to the users so that each user will have access to exactly the same documents as in the original arrangement.