Cryptography
From Caesar ciphers to TLS — how secrets actually stay secret, made rigorous and accessible.
What you'll actually learn
Cryptography courses usually either wave their hands at the math or bury you in it. This track does neither: it starts from why a Caesar cipher is trivially breakable, builds up through symmetric and asymmetric encryption, and lands on exactly how TLS combines both to let two strangers agree on a shared secret over a channel someone else might be reading — the same mechanism protecting every HTTPS connection you've ever made.
What you'll be able to do
You'll be able to explain why "just encrypt it" isn't an answer on its own — why key exchange, not the cipher itself, is usually where real systems actually fail — and trace a TLS handshake step by step instead of treating the padlock icon as unexplainable magic. That distinction is exactly what separates someone who can configure HTTPS from someone who understands why it's actually secure.
Syllabus
Frequently asked
Roughly 1 hour across 9 hands-on quests — you can go at your own pace and pick up exactly where you left off.
Nothing — this is one of the starting points in the skill tree, no prior skill required.
Yes — Cryptography is fully available on the free tier, starting with a free first quest and no payment method required to sign up. Plus and Elite remove pacing limits but don't gate any of the Cryptography curriculum behind a paywall.
Create a free account and begin your first quest — no card required.
Start free