Interactive educational simulation
Breaking the Enigma
Follow the same steps Bletchley Park analysts used in World War II — from encrypting a message to running the Bombe and finding the daily key.
The Stakes
June 1940. Germany controls most of Western Europe. Every Wehrmacht order, every U-boat patrol route, every Luftwaffe sortie is transmitted by radio — encrypted by the Enigma machine, a device the Germans believed unbreakable.
Intercepting the signal was easy. Reading it was another matter. The number of possible Enigma configurations exceeded 158 quintillion — testing one per second would take five billion years.
Three thousand encrypted messages were intercepted every day. And every night at midnight, the Germans changed every key.
— Historian Harry Hinsley, official historian of British Intelligence in WWII
The Enigma Machine
Enigma was an electromechanical cipher. Pressing a key allowed current to flow through four components in sequence:
Keyboard & Lampboard
The operator presses a plaintext letter; a different letter lights up on the lampboard — that is the ciphertext output. Because of the reflector, the same setting also decrypts.
Plugboard (Steckerbrett)
Up to 10 pairs of letters are swapped before and after the rotor path, adding an additional layer of scrambling. The military standard was exactly 10 pairs.
Rotors (Walzen)
Three rotors chosen from a set of five (I–V), each a different letter-substitution wiring. The fast rotor advances one step with every keypress, producing a different substitution each time.
Reflector (Umkehrwalze)
Pairs up the 26 wires so current always returns on a different path. This means a letter can never encrypt to itself — the critical weakness that made breaking possible.
The Codebreakers
Marian Rejewski
Polish mathematician who first broke Enigma in 1932 using pure mathematics. His work — and the bomba machine he inspired — was shared with Britain days before the 1939 invasion of Poland.
Alan Turing
Designed the British Bombe in 1940, a fast electromechanical machine that tested thousands of rotor positions per minute by searching for logical contradictions in intercepted messages.
Gordon Welchman
Added the "diagonal board" to the Bombe in 1940, exploiting plugboard symmetry to double the machine's effectiveness and reduce false stops by about 97%.
Your Workflow
This app guides you through the complete codebreaking process in four steps:
Encrypt
Use the Enigma machine to produce a ciphertext message from your chosen settings.
Find Crib
Slide a guessed plaintext word under the ciphertext to find valid alignment positions.
Build Menu
Convert the crib alignment into a graph of letter relationships that wires the Bombe.
Run Bombe
Scan all 17,576 rotor positions to find the one that produces no contradictions.
⚠ Ring Settings Note
The Bombe assumes ring settings of 1/1/1 (AAA). For the Bombe to find your exact starting position, keep all three ring settings at 1 on the Enigma page. Using non-default ring settings will cause the Bombe to find 0 stops, because the rotor notch positions will be shifted relative to what the Bombe expects.
This is historically accurate: Bletchley Park analysts determined ring settings separately after each Bombe stop by observing middle-rotor turnover positions in traffic, not from the Bombe itself.