{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

CS283 - Lecture 4 - Part 1 - AccessControlMatrix

CS283 - Lecture 4 - Part 1 - AccessControlMatrix - Lecture...

Info icon This preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
GWU CS 172/283 Autumn 2009 Sources: Memon’s notes, Brooklyn Poly Bishop’s Text, Chapter 2 Bishop’s slides, Chapter 2 Lecture 4 – Part 1 - Access Control Matrix
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
GWU CS 172/283 - Autumn 2009 Holmblad - Lecture 04 – Part 1- Rev 20090929 2 Protection State The state of the system is the collection of all current values of all memory locations, secondary storage, registers and other components of the system. The subset of this collection that deals with protection is the protection state of the system. Execution of a command changes the protection state. Ideally, given an authorized state, a set of authorized commands keeps the system in (another) authorized state
Image of page 2
GWU CS 172/283 - Autumn 2009 Holmblad - Lecture 04 – Part 1- Rev 20090929 3 Access Control Matrix (ACM) An Access Control Matrix is a table in which each row represents a subject, each column represents an object, and each entry is the set of access rights for that subject to that object. ACM entry can also be a function that determines rights. E.g. one subject may not be able to access an object when another subject is already writing modifying it
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
GWU CS 172/283 - Autumn 2009 Holmblad - Lecture 04 – Part 1- Rev 20090929 4 Description objects (entities) subjects s 1 s 2 s n o 1 o m s 1 s n Subjects S = { s 1 ,…, s n } Objects O = { o 1 ,…, o m } Rights R = { r 1 ,…, r k } Entries A [ s i , o j ] R A [ s i , o j ] = { r x , …, r y } means subject s i has rights r x , …, r y over object o j
Image of page 4
GWU CS 172/283 - Autumn 2009 Holmblad - Lecture 04 – Part 1- Rev 20090929 5 Example 1 Consider system with two files and two processes. Set of rights is - r,w,x,a,o (read, write, execute, append, own). Can get very large and hence inefficient in general purpose scenarios – seldom used. File 1 File 2 Process 1 Process 2 Process 1 r,w,o r r,w,x,o w Process 2 a r,o r r,w,x,o
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
GWU CS 172/283 - Autumn 2009 Holmblad - Lecture 04 – Part 1- Rev 20090929 6 Example 2 Procedures inc_ctr , dec_ctr , manage Variable counter Rights + , , call counter inc_ctr dec_ctr manage inc_ctr + dec_ctr manage call call call
Image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern