Subject s can read object o only if classs classo

This preview shows page 23 - 30 out of 30 pages.

Subject S can read object O only if class(S) >= class(O) (Simple Security Property) Subject S can write object O only if class(S) <= class(O) (*-Property)
Image of page 23

Subscribe to view the full document.

CT004-3.5-3-Advanced Database Systems Database Security Intuition Idea is to ensure that information can never flow from a higher to a lower security level. E.g., If Dick has security class C, Justin has class S, and the secret table has class S: Dick’s table, Horsie, has Dick’s clearance, C. Justin’s application has his clearance, S. So, the program cannot write into table Horsie. The mandatory access control rules are applied in addition to any discretionary controls that are in effect.
Image of page 24
CT004-3.5-3-Advanced Database Systems Database Security Multilevel Relations Users with S and TS clearance will see both rows; a user with C will only see the 2 nd row; a user with U will see no rows. C Brown Pinto 102 S Red Salsa 101 class color bnam e bid
Image of page 25

Subscribe to view the full document.

CT004-3.5-3-Advanced Database Systems Database Security Multilevel Relations C Brown Pinto 102 S Red Salsa 101 class color bnam e bid If user with C tries to insert <101,Pasta,Blue,C>: Allowing insertion violates key constraint Disallowing insertion tells user that there is another object with key 101 that has a class > C! Problem resolved by treating class field as part of key.
Image of page 26
CT004-3.5-3-Advanced Database Systems Database Security Statistical DB Security Statistical DB: Contains information about individuals, but allows only aggregate queries (e.g., average age, rather than Joe’s age). New problem: It may be possible to infer some secret information! E.g., If I know Joe is the oldest sailor, I can ask “How many sailors are older than X?” for different values of X until I get the answer 1; this allows me to infer Joe’s age.
Image of page 27

Subscribe to view the full document.

CT004-3.5-3-Advanced Database Systems Database Security Why Minimum N is Not Enough By asking “How many sailors older than X?” until the system rejects the query, can identify a set of N sailors, including Joe, that are older than X; let X=55 at this point. Next, ask “What is the sum of ages of sailors older than X?” Let result be S1. Next, ask “What is sum of ages of sailors other than Joe who are older than X, plus my age?” Let result be S2. S1-S2 is Joe’s age!
Image of page 28
CT004-3.5-3-Advanced Database Systems Database Security Summary This lecture has introduced the need for database security, particularly: Recovery measures Access controls Further reading: Raghu Ramakrishna, Database Management Systems, Chapter 21 Slide 29 (of 30)
Image of page 29

Subscribe to view the full document.

CT004-3.5-3-Advanced Database Systems Database Security Next Lesson Concurrency Control Slide 30 (of 30)
Image of page 30
  • Summer '15
  • Database management system, Mandatory Access Control, Statisitical Database

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