1️⃣ System Security Important Notes for Students 2️⃣ System Security Short Notes and Important Questions 3️⃣ System Security Exam Preparation Notes

Network Security & Cryptography Notes

UNIT 1: FUNDAMENTALS OF SECURITY


Security Concepts:

Security is the protection of data, systems, and networks from unauthorized access, attack, or
damage.

Need for Security: To protect confidentiality, integrity, and availability (CIA triad).


Types of Security Attacks:

1. Passive Attack – Monitoring or eavesdropping without altering data.

2. Active Attack – Modification, interruption, or fabrication of data.


Security Services:

Confidentiality, Integrity, Authentication, Non-repudiation, Access Control.


Security Mechanisms:

Encryption, Digital Signatures, Access Control Mechanisms, Firewalls.


Access Control Models:

Access Matrix, Access Control List (ACL), Capability List.

Discretionary Access Control (DAC), Mandatory Access Control (MAC), Role-Based Access
Control (RBAC).



UNIT 2: CRYPTOGRAPHY CONCEPTS AND TECHNIQUES


Plaintext & Ciphertext:

Plaintext is original message; Ciphertext is encrypted message.


Substitution Technique:

Each letter replaced with another (e.g., Caesar Cipher).


Transposition Technique:

Letters rearranged but not replaced.