Security in Computing 5th Edition by Shari Lawrence Pfleeger, Charles P Pfleeger, Jonathan Margulies

Exercise 2

Suppose a per-subject access control list is used. Deleting an object in such a system is inconvenient because all changes must be made to the control lists of all subjects who did have access to the object. Suggest an alternative, less costly means of handling deletion.

Step 1 of 2

Object deletion:

Deletion of an object from the per-subject access list is a complex process, since all the subject lists corresponding to that object will have to be altered. It would be easier to use placeholders to delete the content of the different subject lists. The use of the placeholder is explained with the help of the example given below.