1. Information Security Principles (ESGD4222)
Eng. Mohanned M. Dawoud
Cryptography and Network Security

2. Textbook
Cryptography and Network Security: Principles and Practice; By William Stallings, Fourth Edition
Cryptography and Network Security

3. Grading and Others Grading Homework 20% Mid Term 25%
Report & Presentation %
Final exam %
Cryptography and Network Security

4. Topics Introduction Number Theory
Traditional Methods: secret key system
Modern Methods: Public Key System
Digital Signature and others
Internet Security: DoS, DDoS
Other topics:
secret sharing, zero-knowledge proof, bit commitment, oblivious transfer,…
Cryptography and Network Security

5. Organization Chapters Introduction Number Theory
Conventional Encryption
Block Ciphers
Public Key System
Key Management
Hash Function and Digital Signature
Identification
Secret Sharing
Pseudo-random number Generation
Security
Internet Security
Others
Cryptography and Network Security

6. Cryptography and Network Security Introduction
Xiang-Yang Li
Cryptography and Network Security

7. Introduction
The art of war teaches us not on the likelihood of the enemy’s not coming, but on our own readiness to receive him; not on the chance of his not attacking, but rather on the fact that we have made our position unassailable.
--The art of War, Sun Tzu
Cryptography and Network Security

8. Cryptography
Cryptography (from Greek kryptós, "hidden", and gráphein, "to write") is, traditionally, the study of means of converting information from its normal, comprehensible form into an incomprehensible format, rendering it unreadable without secret knowledge — the art of encryption.
Past: Cryptography helped ensure secrecy in important communications, such as those of spies, military leaders, and diplomats.
Cryptography and Network Security

9. Crypto-graphy, -analysis, -logy
The study of how to circumvent the use of cryptography is called cryptanalysis, or codebreaking.
Cryptography and cryptanalysis are sometimes grouped together under the umbrella term cryptology, encompassing the entire subject.
In practice, "cryptography" is also often used to refer to the field as a whole; crypto is an informal abbreviation.
Cryptography and Network Security

10. Approaches to Secure Communication
Steganography
“covered writing”
hides the existence of a message
Cryptography
“hidden writing”
hide the meaning of a message
Cryptography and Network Security

11. Stenography Example
Last 2 bits
Cryptography and Network Security

12. Network Security Model
Trusted Third Party
principal
principal
Security transformation
Security transformation
attacker
Cryptography and Network Security

13. Attacks, Services and Mechanisms
Security Attacks
Action compromises the information security
Could be passive or active attacks
Security Services
Actions that can prevent, detect such attacks.
Such as authentication, identification, encryption, signature, secret sharing and so on.
Security mechanism
The ways to provide such services
Detect, prevent and recover from a security attack
Cryptography and Network Security

14. Attacks Passive attacks Active attacks Interception
Release of message contents
Traffic analysis
Active attacks
Interruption, modification, fabrication
Masquerade
Replay
Modification
Denial of service
Cryptography and Network Security

15. Information Transferring
Cryptography and Network Security

16. Attack: Interruption Cut wire lines, Jam wireless signals,
Drop packets,
Cryptography and Network Security

17. Attack: Interception Wiring, eavesdrop
Cryptography and Network Security

18. Attack: Modification Replaced info intercept
Cryptography and Network Security

19. Also called impersonation
Attack: Fabrication
Also called impersonation
Cryptography and Network Security

20. Attacks, Services and Mechanisms
Security Attacks
Action compromises the information security
Could be passive or active attacks
Security Services
Actions that can prevent, detect such attacks.
Such as authentication, identification, encryption, signature, secret sharing and so on.
Security mechanism
The ways to provide such services
Detect, prevent and recover from a security attack
Cryptography and Network Security

21. Important Services of Security
Confidentiality, also known as secrecy:
only an authorized recipient should be able to extract the contents of the message from its encrypted form. Otherwise, it should not be possible to obtain any significant information about the message contents.
Integrity:
the recipient should be able to determine if the message has been altered during transmission.
Authentication:
the recipient should be able to identify the sender, and verify that the purported sender actually did send the message.
Non-repudiation:
the sender should not be able to deny sending the message.
Cryptography and Network Security

22. Homework
Describe two of the functions listed in Table 1.1 of the Textbook in half page for each one, be ready to discuss them in the next lecture.
Deadline: Tuesday 3/3/2009