The document discusses network security and cryptography. It covers access matrices and lists, multilevel security models, security levels, trusted systems, and complete mediation, isolation, and verifiability as methods for enhancing system defenses against intruders and malicious programs. The document is authored by Sumita Das and references William Stallings' book on cryptography and network security principles and practices.

1. TRUSTED SYSTEMS
Network Security And Cryptography
By:-
SUMITA DAS

2.  To enhance the ability of a system to defend against-
Intruders
malicious programs.
Created by Sumita Das

3. Access Matrix:
 Subject
 Object
 Access right
Created by Sumita Das

4. Access Control List:
Decomposition of the matrix by columns
Created by Sumita Das

5. Capability list:
Decomposition of the matrix by rows
Created by Sumita Das

6.  Protect data and resources on the basis of levels of
security.
Unclassified(U)
Confidential(C)
Secret(S)
Top Secret(TS)
Created by Sumita Das

7.  Multilevel security: Multiple categories or levels of
data
 Multilevel secure system must enforce:
 No read up (Simple Security Property)
 No write down(Property)
 Security levels may be linear or latticed
Created by Sumita Das

8.  Provides multilevel security for a data processing
system
 Controlling element in the hardware and operating
system of a computer that regulates the access of
subjects to objects on the basis of security parameters
of the subject and object.
Created by Sumita Das

9. Created by Sumita Das

10.  Complete mediation
 Isolation
 Verifiability
Created by Sumita Das

11.  Secure, trusted operating systems are one way to secure
against Trojan Horse attacks
Created by Sumita Das

12. [1]William Stallings, “Cryptography and
Network Security Principles and Practices”,
Fourth Edition
Created by Sumita Das