Cybersecurity Module 3: Introduction to Cryptography

Cryptography forms the backbone of modern cybersecurity - enabling secure communication, privacy, and digital trust. This module introduces essential encryption methods and breaks down how they work in practice.

You will compare symmetric and asymmetric encryption, see how algorithms like RSA support HTTPS, and explore a classic Caesar cipher example to reinforce how substitution ciphers work.

🔎 What you will learn

• 🔐 How symmetric key encryption protects large volumes of data quickly
• 🔑 How asymmetric public key encryption enables secure communication over open networks
• 🌐 Where protocols like RSA and HTTPS fit into real-world secure communication
• 🧩 How the Caesar cipher and ROT13 demonstrate the principles behind substitution ciphers

🔐 Symmetric key encryption

Symmetric encryption uses a single shared key for both encryption and decryption. It is fast and widely used for protecting files and data in transit.

• 🔒 AES (Advanced Encryption Standard)
• 🔒 DES (Data Encryption Standard)
• 💽 BitLocker (full disk encryption on Windows)

🔑 Asymmetric public key encryption

Asymmetric encryption uses two keys - a public key to encrypt and a private key to decrypt. It underpins secure internet protocols and digital identity.

• 🧮 RSA (used for digital signatures and encryption)
• 📡 Diffie-Hellman (secure key exchange)
• 🔐 ElGamal (used in hybrid encryption systems)
• 🌐 HTTPS (powered by SSL/TLS protocols)

📊 Symmetric vs asymmetric - key differences

• Symmetric: Much faster and ideal for bulk data - but requires secure key sharing.
• Asymmetric: Well suited to open communication and identity - but computationally slower.

🔄 Caesar cipher (ROT13 demo)

The Caesar cipher is a classic encryption technique. Each letter is shifted by a fixed amount. ROT13 is a common example that shifts letters by 13 positions.

💡 Tip: Try creating your own Caesar cipher encoder or decoder as a coding challenge.