Question 7 (2, 2, 2) The model of protection in a computer system can be viewed

Question

Question 7 (2, 2, 2) The model of protection in a computer system can be viewed as an access matrix, with rows representing subjects, and columns representing objects. Each entry in the matrix represents the access rights of the subject to the object. The existing operating systems implement either the row view or the column view of the access matrix. a. What is the resulting system if the rows are implemented? What are the advantages and disadvantages of the row implementation? b. What is the resulting system if the columns are implemented? What are the advantages and disadvantages of the column implementation? How would you classify the protection system implemented in UNIX in terms of the access matrix? Justify your answer.

Explanation / Answer

a. Answer

Each row corresponds to the access rights of a subject over all objects it can use. If the subject has no rights over an object no information is stored. This approach is known as capability lists.

Advantage:

Disadvantage:

b. Answer

Each column represents the access rights held over this object. No information is stored about domains that have no access. This approach is known as access lists.

Advantage:

Disadvantage:

c. Answer

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