Crypto

Classic ciphers and cipher machines that run in your browser. Nothing you type leaves the page.

Classical ciphers

Pen-and-paper ciphers, from the simplest up.

• Caesar and ROT13Shift letters along the alphabet, and crack a Caesar message by trying all 25 keys.
• VigenèreA keyword picks a different Caesar shift for each letter. Includes a cracker that finds the key length, then the key.
• One-Time PadA random key as long as the message, used once. Shows why it can't be broken, and how reusing a pad breaks it.

Cipher machines

Electromechanical machines from the twentieth century.

• Enigma MachineA working simulation of the Enigma I, M3, and M4, with the historical rotor wiring, rotor stepping, ring settings, and plugboard.