Computer Science and Engineering#

Central Institute of Technology Kokrajhar

Lecture Notes: Cryptography & Network Security (DCSE504)#

Credits: 6

L-T-P: 3-0-0

Module 1: Introduction to Cryptography & Network Security (4 Hours)

1.1 The Need for Security

• Importance of protecting information in the digital age
• Threats from unauthorized access, modification, and interception
• Real-world examples of security breaches

1.2 Principles of Security (CIA triad)

• Confidentiality: Ensuring only authorized users can access information.
• Integrity: Guaranteeing data remains unaltered during transmission or storage.
• Authentication: Verifying the identity of a user or system.
• Non-repudiation: Preventing someone from denying an action they performed.
• Access Control: Regulating access to specific resources based on permissions.
• Availability: Ensuring authorized users can access information and systems when needed.

1.3 Types of Attacks (4 hours)

• Passive Attacks: Eavesdropping (snooping), traffic analysis
• Active Attacks: Tampering with data, masquerading as another user, denial-of-service attacks
• Malicious Software: Viruses, worms, Trojan horses
• Social Engineering: Techniques to trick users into revealing information or taking actions.
• Specific Attacks:
• Spoofing: Forging source address to impersonate another user/system.
• Phishing: Deceptive emails or websites tricking users into revealing personal information.
• Pharming: Redirecting users to malicious websites by manipulating DNS records.

Module 2: Concept and Techniques of Cryptography (8 Hours)

2.1 Plain Text and Cipher Text

• Plain text: Original, unencrypted message.
• Cipher text: Encrypted message, unreadable without a decryption key.

2.2 Substitution Techniques (4 hours)

• Replacing characters in the plain text with different characters or symbols.
• Examples: Caesar Cipher, Monoalphabetic substitution, Polyalphabetic substitution (Vigenere Cipher,Playfair Cipher, Hill Cipher).

2.3 Transposition Techniques (2 hours)

• Rearranging the order of characters in the plain text.
• Examples: Rail Fence Technique, Simple Columnar Transposition.

2.4 Encryption and Decryption

• Processes of transforming plain text to cipher text and vice versa.

2.5 Symmetric and Asymmetric Key Cryptography

• Symmetric Key: Same key used for encryption and decryption (shared secret).
• Asymmetric Key: Public and private key pair used for encryption and decryption (public key for encryption,private key for decryption).

2.6 Steganography

• Hiding the existence of a message within another medium (image, audio).

Module 3: Symmetric Key Algorithms (10 Hours)

3.1 Algorithm Types and Modes of Operation (ECB, CBC, CFB, OFB, CTR)

• Different encryption algorithms used for symmetric key cryptography.
• Modes of operation determine how blocks of data are processed during encryption/decryption.

3.2 Overview of Symmetric Key Cryptography

• Advantages and limitations of symmetric key algorithms.

3.3 Data Encryption Standard (DES)

• A widely used, now outdated, symmetric key algorithm.
• Understanding the DES algorithm structure and limitations.

3.4 Advanced Encryption Standard (AES)

• The current standard for symmetric key encryption, considered more secure than DES.
• Exploring the key features and strengths of AES.

Module 4: Asymmetric Key Algorithms (10 Hours)

4.1 Overview of Asymmetric Key Cryptography

• Advantages and disadvantages compared to symmetric key algorithms.
• Applications for public key cryptography (secure communication, digital signatures).

4.2 The RSA Algorithm (Rivest–Shamir–Adleman)

• A widely used public key cryptography algorithm.
• Understanding the key generation process and mathematical foundation of RSA.
• Exploring practical applications of RSA (digital signatures, key exchange).

4.3 Symmetric and Asymmetric Key Cryptography Together

• Hybrid cryptosystems utilizing both symmetric and asymmetric keys for efficiency and security.
• Common use cases for hybrid systems.

4.4 Digital Signature, Message Digest (Hashing), MD5, Secure Hash Algorithm (SHA), Hash-based Message Authentication Code (HMAC)

• Digital signatures for message authentication and non-repudiation.
• Message digest algorithms (MD5, SHA) for data integrity verification.
• HMAC combining message digest with a secret key for message authentication.

Module 5: Authentication (5 Hours)

5.1 Authentication Basics

• Importance of user and system authentication for secure access.
• Different authentication factors (something you know, something you have, something you are).

5.2 Password-Based Authentication

• Common method for user authentication, with inherent vulnerabilities (weak passwords, password cracking).
• Techniques for strengthening password security (password complexity requirements, password hashing).

5.3 Public Key Infrastructures (PKI)

• A framework for managing digital certificates and public keys for secure communication.
• Components of PKI (Certificate Authorities, Registration Authorities, digital certificates).

5.4 Certification Authorities (CAs) and Key Distribution Centers (KDCs)

• Roles of CAs in issuing and managing digital certificates.
• KDCs and their role in securely distributing keys in Kerberos authentication.

5.5 Kerberos

• A network authentication protocol using a central KDC for secure user authentication.
• Understanding the Kerberos authentication process and its benefits.

Module 6: Firewall (5 Hours)

6.1 Firewall Characteristics

• Definition of a firewall and its role in network security.
• Types of firewalls (packet filtering, stateful inspection, application-level).

6.2 Firewall Capabilities and Limitations

• Functionality of firewalls in filtering traffic and controlling access.
• Recognizing limitations of firewalls (not a complete security solution, can be bypassed by sophisticated attacks).

6.3 Firewall Configuration

• Basic principles of firewall configuration for different network environments.
• Importance of proper firewall configuration for effective security.

6.4 Trusted Systems and Virtual Private Networks (VPNs)

• Trusted systems with enhanced security measures to resist attacks.
• VPNs for creating secure encrypted tunnels over public networks.