1. DDBMS Security
- Bakul Gada

2. Overview Introduction to Database Security
Security Issues in centralized databases
Security issues in Distributed Databases

3. Introduction Data security Two aspects
Protect data against unauthorized access.
Two aspects
Data protection.
Authorization Control.

4. Aspects of Data security
Data Protection
Can be achieved using data encryption techniques.
Authorization Control
It ensures that only authorized users perform, operations that they are allowed to perform on the database.
Reference: Principles of Distributed Database Systems –
M. Tamer Ozsu & Patrick Valduriez

5. Authorization Control
It includes two main issues
Access control
Unauthorized Access to data should not be allowed.
Integrity
Only authorized users should be allowed to modify data in the database.

6. Centralized Authorization Control
Allowing a user to do a particular operation on the subsets of database.
In RDBMS these subsets can be defined using Views.
Views allow limited access to database

7. Methods of Authorization Control
Discretionary Access Control
Based on privileges or access rights
Mandatory Access control
Based on policies that can’t be changed by individual users
Reference: Database Management Systems - R.Ramakrishnan /
J Gehrke (2nd ed.)

8. Discretionary Access Control
This can be implemented at two levels
Account Level
Set privileges for each account on different relations
Relation Level
Set privileges to access each individual relation or view
Reference: Database Management Systems - R.Ramakrishnan /
J Gehrke (2nd ed.)

9. GRANT and REVOKE commands
SQL supports discretionary access control through grant and revoke commands.
Syntax for GRANT and REVOKE commands
GRANT < operation type(s)> ON <object> TO <user(s)>
REVOKE < operation type(s)> ON <object> TO <user(s)>
Reference: Principles of Distributed Database Systems –
M. Tamer Ozsu & Patrick Valduriez

10. Mandatory Access Control
Users classified based on security classes
Top Secret (TS)
Secret (S)
Confidential (C)
Unclassified (U)

11. Bell –LaPadula Model Most Popular Model for multilevel security.
Two restrictions are enforced on data access based on subject/object classification.
A subject S is not allowed to read an object O unless class(S)  class(O)
A subject S is not allowed to write an object O unless class(S)  class(O)
Reference: Bell D.E and LaPadula L.J., "Secure Computer Systems: Unified Exposition and Multics Interpretation", THE MITRE Corporation, July 1975.

12. Authorization Control in Distributed Environment.
More Complex.
Remote User Authentication
Management of distributed authorization rules
Handling of Views and User Groups
Reference: Principles of Distributed Database Systems –
M. Tamer Ozsu & Patrick Valduriez

13. Solution
Information for authenticating users is replicated at all sites.
All sites of the DDBMS identify & authenticate themselves similarly to the way users do.

14. Integrity How to guarantee database consistency ?
A database is said to be consistent if it satisfies the set of integrity constraints.
Concurrency control techniques
Locking Technique
Timestamp Ordering
Multiversion Concurrency Control
Validation Concurrency Control
Ref: Fundamentals of Database Systems - Elmasri & Navathe (3rd ed)

15. Integrity in Distributed Databases
Concurrency Control techniques need to be employed in Distributed databases.
Two general classes
Pessimistic Concurrency Control
Optimistic Concurrency Control

16. Summary
Security issues in Distributed Databases are more complex as compared to Centralized Databases. But they can be taken care of through careful study.
Future
Right now, RDBMS is a better choice for distributed applications. OODBMSs are much more difficult to implement in a distributed environment. Steps are being taken to do the same.