Cryptography for Developers
Seven lessons on the cryptographic primitives that appear in every production system — hashing, password storage, symmetric encryption, public-key cryptography, key exchange, and TLS. Each lesson pairs a written explanation with a Computerphile video and a hands-on browser tool.
Curriculum
- 1
What Is a Hash Function?
Hash functions turn any input into a fixed-length fingerprint. Understanding what they guarantee — and what they don't — is the foundation for everything else in this course.
6 min read·Video included·SHA-256 / SHA-512 Tool - 2
Why Storing Passwords as Hashes Isn't Enough
A plain SHA-256 hash of a password can be cracked in seconds. Salting fixes part of the problem. Slowness fixes the rest. Here's why you need both.
7 min read·Video included·MD5 Tool - 3
How Attackers Actually Crack Password Databases
Not brute force — dictionary attacks, rule-based mangling, and GPU farms. Understanding the attack tells you exactly what defence looks like.
7 min read·Video included·Bcrypt Tool - 4
Symmetric Encryption: How AES Keeps Data Secret
Hashing proves integrity. Encryption proves secrecy. AES-256 is the current standard for symmetric encryption — here's what it actually does and where it falls short.
7 min read·Video included·AES Encrypt / Decrypt Tool - 5
Asymmetric Cryptography: How Public and Private Keys Work
Symmetric encryption has a problem: how do you share the key? Public-key cryptography solves that. It's also the basis for digital signatures, certificates, and HTTPS.
8 min read·Video included·RSA Encrypt / Decrypt Tool - 6
Key Exchange: How Two Strangers Agree on a Secret
Diffie-Hellman lets two parties derive a shared secret over a public channel — without ever transmitting the secret itself. It's the mechanism behind every TLS connection.
7 min read·Video included·Diffie-Hellman + MITM Tool - 7
TLS: How Your Browser Knows It's Talking to the Right Server
TLS combines everything from this course — hashing, symmetric encryption, public-key cryptography, and key exchange — into the protocol that secures the web. Here's how it fits together.
8 min read·Video included·Digital Signatures Tool
All tools used in this course run entirely in your browser — nothing is sent to a server. Videos are from Computerphile.