Learn cryptography by breaking real ciphers, step by step.
Never encrypted anything? Begin with the Caesar shift — the classic first cipher — and learn by breaking messages.
New to ciphers? Start with the classics and work your way up — every cipher comes with guided learning and a breaking tool.
Already know your stuff? Jump straight to the tool — every cipher in the collection, no tracking, no accounts.
Climb from the trivial to Enigma. Every rung: a tool and a guided course.
encoding, not encryption · trivial to break
substitution cipher · trivial to break
substitution cipher · trivial to break
substitution cipher · trivial to break
substitution cipher · trivial to break
substitution cipher · trivial to break
transposition cipher · trivial to break
substitution cipher · easy to break by hand
substitution cipher · easy to break by hand
transposition cipher · easy to break by hand
substitution cipher · hard to break by hand
polyalphabetic substitution cipher · hard to break by hand
polyalphabetic substitution cipher · hard to break by hand
polyalphabetic substitution cipher · hard to break by hand
polyalphabetic substitution cipher · medium to break by hand
fractionation + transposition cipher · hard to break by hand
polyalphabetic substitution cipher · easy to break by hand
polyalphabetic substitution cipher · hard to break by hand
Not pen-and-paper, but handy in the digital world: Base64 · Off the ladder, a hidden page: Arne Saknussemm’s runic parchment
✓ What's built
→ What's next