Enigma Machine Simulator

The Enigma Machine, Simulated

This is an interactive model of the WWII German Enigma cipher machine. It reproduces the real electromechanical components and their behavior so you can encrypt and decrypt messages exactly as an operator would have in the 1940s:

• Rotors I–V with their authentic wirings and turnover notches
• Reflector (Umkehrwalze) that sends the signal back through the rotors
• Plugboard (Steckerbrett) for additional letter swaps
• Signal visualization tracing the current path through each component

How Enigma Worked

Pressing a key sent current through the plugboard, forward through the rotor stack, into the reflector, back through the rotors, and out to light a lamp. Crucially, the rightmost rotor stepped on every keypress, so the substitution changed letter by letter — a polyalphabetic cipher rather than a simple one. The same machine settings decrypt: Enigma is reciprocal, so encryption and decryption are the same operation.

Its Fatal Flaw

The reflector guaranteed that no letter ever encrypted to itself. That single constraint, plus operator habits and predictable message cribs, gave Allied cryptanalysts at Bletchley Park the leverage to break it with the Bombe. It is a foundational lesson in cryptography: a large keyspace (Enigma's was enormous) does not guarantee security if the design leaks structure.

Why Use This

• Learn polyalphabetic substitution hands-on.
• See why key management and operator discipline matter as much as the algorithm.
• Study a real historical system for coursework or curiosity.

For a gentler first step into substitution ciphers, try the Caesar Cipher, then return here to see how rotor stepping defeats simple frequency analysis.