Class 5

Class 5 – Cryptography

Class Material: Week 3 – Day 1 – Cryptography

This session introduces the foundational concepts of cryptography, explaining how it secures digital communication and protects data from unauthorized access. Students explore key terminology, encryption types, and classical cipher techniques through interactive learning.

Key Topics Covered:

Introduction to Cryptography
Cryptography is the science of securing data by transforming it into unreadable formats. It ensures privacy, authenticity, data integrity, and non-repudiation across digital platforms.

Importance of Cryptography
Used to protect passwords, credit card data, private communications, and prevent identity theft, cryptography underpins trust in modern digital systems including online banking and government operations.

Key Terms

• Plaintext: Original readable message

• Ciphertext: Encrypted, unreadable version of plaintext

• Encryption/Decryption: Process of converting data to/from ciphertext using keys and algorithms

• Key: Secret value used in encryption and decryption

• Algorithm: Set of rules for transforming plaintext into ciphertext

Types of Cryptography

• Symmetric: Both sender and receiver share the same key

• Asymmetric: Uses a public key for encryption and a private key for decryption

Classical Ciphers

• Caesar Cipher: Shifts letters by a fixed number

• Vigenère Cipher: Uses a keyword to vary letter shifts

• Substitution Cipher: Replaces each letter with a different one based on a fixed system

The session effectively lays the groundwork for understanding the principles of secure communication. Through real-world analogies and gamification, students develop a strong grasp of classical encryption techniques and their relevance in modern cybersecurity.