Polyinstantiation - Introduction to Database Security - Lecture Slides, Slides of Network security

Download Polyinstantiation - Introduction to Database Security - Lecture Slides and more Slides Network security in PDF only on Docsity!

1

Polyinstantiation

2

Polyinstantiation

• Definition and need for polyinstantiation
• Sea View model
• Jajodia – Sandhu model

4

Definition and need for

polyinstantiation

• Polyinstantiation can affect relations, tuples and data elements
• Polyinstantiation arises because subjects with different classes are allowed to operate on the same relations
• Polyinstantiated relations are relations with different access classes
• Polyinstantiated tuples (also called entity polyinstantiation) are tuples with the same primary key but with different access classes associated to the primary keys

5

Definition and need for

polyinstantiation

• Polyinstantiated elements (also called

attribute polyinstantiation) are elements of

an attribute which have different access

classes but are associated with the same

primary key and key class

• Polyinstantiation occurs as one of:
  • Visible polyinstantiation
  • Invisible polyinstantiation

7

Example of polyinstantiated relation

User Cuser Dept Cdept Salary^ Csalary TC

Bob S Math S 10K S S

Ann S CIS S 30K TS TS

Sam TS CIS TS 30K TS TS

Figure 1

8

Example of polyinstantiated tuple

User Cuser Dept Cdept Salary^ Csalary TC

Bob S Math S 10K S S

Ann S CIS S 30K TS TS

Sam TS CIS TS 30K TS TS

Sam S Math S 10K S S

Figure 2

10

Example of polyinstantiated element

User Cuser Dept Cdept Salary^ Csalary TC

Bob S Math S 10K S S

Ann S CIS S 20K S S

The view of the table for a subject with classification S based on the previous table for a polyinstantiated element

Figure 4

11

Polyinstantiation

• For read operations, subjects have read

access to instances of multilevel relations

accessing data at their level or below

• For write (insert or update) operations, the

effect depends on the access level of

dominated by, dominates or incomparable

13

Polyinstantiation

• Suppose an S-subject (i.e., a subject with

classification S) wants to execute the operation UPDATE EMPLOYEE SET Salary = ‘20K’ WHERE Name = ‘Ann’ The operation is applied to Figure 1 and the result will be Figure 3

In this example, the subject clearance is dominated by the access class of data

14

Polyinstantiation

• Suppose a TS-subject (i.e., a subject with classification TS) wants to execute the operation UPDATE EMPLOYEE SET Dept = ‘Math’ WHERE Name = ‘Ann’ The operation is applied to Figure 3 and the result will be Figure 5 given next, where multiple rows are added

In this example, the subject clearance dominates the access class of data

16

Polyinstantiation

• In Figure 5, the two rows added have the

classification of TS for the Dept field for

Ann because these tuples were added by

a TS-subject. They should not be visible

for an S-subject.

17

Polyinstantiation

• Suppose a TS-subject (i.e., a subject with classification TS) wants to execute the operation UPDATE EMPLOYEE SET Dept = ‘CIS’, Salary=‘20K’ WHERE Name = ‘Bob’ The operation is applied to Figure 3 and the result will be Figure 6 given next, where multiple rows are added

In this example, the subject clearance dominates the access class of data

19

Polyinstantiation

• In Figure 6, the three rows added have the

classification of TS for the tuple because

these tuples were added by a TS-subject.

They should not be visible for an S-

subject.

20

Sea View Model

• SEcure dAta VIEW was developed by Lunt,

Denning, et al in 1987 in California

• Sea View model actually improved upon the

concept of polyinstantiation developed by Hinke and Schaefer

• Model has two layers:
  • MAC (Mandatory Access Control)
  • TCB (Trusted Computing Base)
• MAC enforces the security policy of the Bell-

LaPadula and Biba models