CS8792 - Cryptography and Network Security

this is an engineering subject.this consist of
pgno: 5 - Information security in past & present
pgno: 7 - Aim of Course
pgno: 8 - OSI Security Architecture
pgno: 9 - Security Goals – CIA Triad
pgno: 13 - Aspects of Security
pgno: 17 - ATTACKS
pgno: 22 - Passive Versus Active Attacks
pgno: 23 - SERVICES AND MECHANISMS

1. CS8792 - Cryptography and Network Security VKP

2. Unit – I INTRODUCTION Security trends - Legal, Ethical and Professional Aspects of Security, Need for Security at Multiple levels, Security Policies - Model of network security – Security attacks, services and mechanisms – OSI security architecture – Classical encryption techniques: substitution techniques, transposition techniques, steganography- Foundations of modern cryptography: perfect security – information theory – product cryptosystem – cryptanalysis.

3. What security is about in general? Security is about protection of assets Prevention Detection Reaction

4. Internet shopping example Prevention encrypt your order and card number, enforce merchants to do some extra checks, using PIN even for Internet transactions, don’t send card number via Internet Detection an unauthorized transaction appears on your credit card statement Reaction complain, dispute, ask for a new card number etc

5. Information security in past & present Traditional Information Security keep the cabinets locked put them in a secure room human guards electronic surveillance systems in general: physical and administrative mechanisms Modern World Data are in computers Computers are interconnected

6. Definitions Computer Security - generic name for the collection of tools designed to protect data and to thwart hackers Network Security - measures to protect data during their transmission Internet Security - measures to protect data during their transmission over a collection of interconnected networks

7. Aim of Course our focus is on Internet Security which consists of measures to deter, prevent, detect, and correct security violations that involve the transmission & storage of information

8. OSI Security Architecture ITU-T X.800 “Security Architecture for OSI” defines a systematic way of defining and providing security requirements

9. Security Goals – CIA Triad

10. Confidentiality Confidentiality is probably the most common aspect of information security. We need to protect our confidential information . An organization needs to guard against those malicious actions that endanger the confidentiality of its information.

11. Integrity Information needs to be changed constantly. Integrity means that changes need to be done only by authorized entities and through authorized mechanisms.

12. Availability The information created and stored by an organization needs to be available to authorized entities. Information needs to be constantly changed, which means it must be accessible to authorized entities.

13. Aspects of Security consider 3 aspects of information security: security attack security services security mechanism

14. Security Attack Any action that compromises the security of information owned by an organization Information security: how to prevent attacks, or failing that, to detect attacks on information-based systems Note: often threat & attack mean same Focus on generic types of attack Passive & Active

15. Passive Attacks

16. Active Attacks

17. ATTACKS The three goals of security ¾ confidentiality, integrity, and availability ¾ can be threatened by security attacks.

18. Figure 1.2 Taxonomy of attacks with relation to security goals 1.2 Continued

19. 1.2.1 Attacks Threatening Confidentiality Snooping refers to unauthorized access to or interception of data. Traffic analysis refers to obtaining some other type of information by monitoring online traffic.

20. 1.2.2 Attacks Threatening Integrity Modification means that the attacker intercepts the message and changes it. Masquerading or spoofing happens when the attacker impersonates somebody else. Replaying means the attacker obtains a copy of a message sent by a user and later tries to replay it. Repudiation means that sender of the message might later deny that she has sent the message; the receiver of the message might later deny that he has received the message.

21. 1.2.3 Attacks Threatening Availability Denial of service (DoS) is a very common attack. It may slow down or totally interrupt the service of a system.

22. 1.2.4 Passive Versus Active Attacks Table 1.1 Categorization of passive and active attacks

23. SERVICES AND MECHANISMS ITU-T provides some security services and some mechanisms to implement those services. Security services and mechanisms are closely related because a mechanism or combination of mechanisms are used to provide a service..

24. 1.3.1 Security Services Figure 1.3 Security services

25. Security Services (X.800) Authentication - assurance that the communicating entity is the one claimed Access Control - prevention of the unauthorized use of a resource Data Confidentiality –protection of data from unauthorized disclosure Data Integrity - assurance that data received is as sent by an authorized entity Non-Repudiation - protection against denial by one of the parties in a communication

26. 1.3.2 Security Mechanism Figure 1.4 Security mechanisms

27. Security Mechanism feature designed to detect, prevent, or recover from a security attack no single mechanism that will support all services required however one particular element underlies many of the security mechanisms in use: cryptographic techniques Crypto Secret Writing graphy

28. Security Mechanisms (X.800) specific security mechanisms: encipherment, digital signatures, access controls, data integrity, authentication exchange, traffic padding, routing control, notarization pervasive security mechanisms: trusted functionality, security labels, event detection, security audit trails, security recovery

29. 1.3.3 Relation between Services and Mechanisms Table 1.2 Relation between security services and mechanisms

30. Model for Network Security

31. Some Basic Terminology Plaintext - original message Ciphertext - coded message Cipher - algorithm for transforming plaintext to ciphertext Key - information used in cipher known only to sender/receiver Encipher (encrypt) - converting plaintext to ciphertext Decipher (decrypt) - recovering ciphertext from plaintext Cryptography - study of encryption principles/methods Cryptanalysis (codebreaking) - study of principles/ methods of deciphering ciphertext without knowing key Cryptology - field of both cryptography and cryptanalysis

32. Data Transmission Steps PT PT CT CT Encryption Transmission Decryption X – Plain text Y – Cipher text K – Key Y = E k (X) X = D k (Y)

33. Cryptography Characterize cryptographic system by: Type of encryption operations used Substitution / Transposition / Product Number of keys used Single-key or Private / Two-key or Public Way in which plaintext is processed Block /

34. Cryptanalysis Objective to recover key not just message General approaches: Cryptanalytic attack Knowledge of algorithm and some part of plaintext Brute-force attack Try every possible key on cipher text to get a meaningful plain text

35. END