Hash Functions and Message Authentication Codes

IntermediateFree5 modules · 15 lessons · ~2 min

About this course

A practitioner-level course on what a cryptographic hash function actually guarantees, why the SHA family replaced MD5 and SHA-1, and how message authentication codes, key derivation and password hashing each solve a genuinely different problem despite all starting from a hash function. You will finish able to pick the right construction, HMAC, a polynomial MAC, HKDF or a memory-hard function, for a given job, and to recognise the length extension mistake that keeps recurring when the wrong one is chosen.

What you'll learn

Hash Function Properties

What a Cryptographic Hash Function Must Guarantee: Preimage, Second-Preimage and Collision Resistance
The Birthday Bound: Why Collision Resistance Costs Half the Bits
Hash Function Construction: Merkle-Damgard and Sponge Designs

The SHA Family and What Broke

The SHA Family: SHA-1, SHA-2 and SHA-3 Compared
What Happened to MD5 and Why It Is Broken
What Happened to SHA-1 and What Its Break Actually Cost

Message Authentication Codes

Why a Hash Alone Cannot Authenticate a Message
HMAC Construction: Why It Is Built the Way It Is
Polynomial MACs: Poly1305 and the GHASH Construction Behind GCM

Key Derivation and Password Hashing

01Hash Function Properties3 lessons

What a Cryptographic Hash Function Must Guarantee: Preimage, Second-Preimage and Collision Resistance
The Birthday Bound: Why Collision Resistance Costs Half the Bits
Hash Function Construction: Merkle-Damgard and Sponge Designs

02The SHA Family and What Broke3 lessons

Common questions

How much does Safeguard Academy cost?

Nothing. Every course, exam, and certificate on the catalog is free — including retakes. All you need is a free Safeguard account.

What are the prerequisites?

None. The flagship course, Safeguard Certified Practitioner, is a beginner-level course — basic familiarity with how software is built helps, but every exam question is answerable from the lessons themselves.

Key Derivation Functions: Turning One Secret Into Many

Why a Fast Hash Is the Wrong Tool for Passwords

Memory-Hard Functions, Salts and Peppers: Argon2, scrypt and bcrypt Compared

Length Extension and Bringing It Together

The Length Extension Attack: Why It Exists and Which Constructions Are Immune
Choosing a Hash-Based Construction in Practice: A Decision Table
Bringing It Together: A Worked Review of a Hash-Based System

The SHA Family: SHA-1, SHA-2 and SHA-3 Compared

What Happened to MD5 and Why It Is Broken

What Happened to SHA-1 and What Its Break Actually Cost

03Message Authentication Codes3 lessons

Why a Hash Alone Cannot Authenticate a Message
HMAC Construction: Why It Is Built the Way It Is
Polynomial MACs: Poly1305 and the GHASH Construction Behind GCM

04Key Derivation and Password Hashing3 lessons

Key Derivation Functions: Turning One Secret Into Many
Why a Fast Hash Is the Wrong Tool for Passwords
Memory-Hard Functions, Salts and Peppers: Argon2, scrypt and bcrypt Compared

05Length Extension and Bringing It Together3 lessons

The Length Extension Attack: Why It Exists and Which Constructions Are Immune
Choosing a Hash-Based Construction in Practice: A Decision Table
Bringing It Together: A Worked Review of a Hash-Based System2 min

What happens if I fail the exam?

You can retake it after a 24-hour cooldown, as many times as you need. Retakes are free, and each attempt draws a fresh random set of questions.

How long is a certificate valid?

The Safeguard Certified Practitioner credential is valid for 24 months from issue. The expiry date is printed on the certificate and shown live on its public verification page. Renewing means passing the current exam again.