How Ciphers, Hashes, MACs, AEAD Compose

This book introduces several cryptographic primitives. They are not isolated tools. They are building blocks that compose into secure systems.

This section shows how they connect.

Each following chapter will explore one of these components in depth.

The Four Core Primitives

Provides confidentiality. Encrypts data using a shared secret key.

Provides integrity fingerprinting. Maps arbitrary data to a fixed-size digest. No key.

Provides integrity + authenticity. Built using a secret key (often from a hash construction such as HMAC).

Provides confidentiality + integrity + authenticity in a single construction.

Hash → Used to build MAC (HMAC)

Cipher + Authenticator → Used to build AEAD

AEAD → Used in modern secure communication protocols

🚨 Security rule 🚨

Never invent your own composition.

❌ Bad idea: encrypt(data) + hash(data)

✅ Correct approach: Use AEAD.