Enigma
Pressing a letter key sends one electrical signal through the machine. The plugboard may swap the letter, the rotors change it, the reflector sends the same signal back through the rotors, and one output bulb lights up. The lit bulb is the encrypted letter.
Machine parts
Plugboard ?
Click two sockets to place a cable. A cable swaps those two letters. Click a connected socket to remove its cable.
Message
The historical machine had letter keys only. Spaces and punctuation are removed before encoding.
One-letter path
Follow the arrows. Each box shows the letter after that part. N→I means this part changed N into I. Rotor boxes also show their current window letter.
Bombe
A Bombe starts with a crib: a guessed word or phrase from the original message. It tries every place the crib could fit under the ciphertext, then searches for Enigma settings whose plugboard consequences do not contradict each other.
Crib and ciphertext
Bombe search
A crib placement is where the guessed text sits under the ciphertext. A stop is a candidate machine setting that survives the Bombe contradiction test. The standard search fixes the ring setting, which keeps the search practical in a browser. Exhaustive ring search is available when needed.
Chosen setup
Menu
The menu uses the same socket-board style as the Enigma plugboard, but it is not a guessed plugboard. Each line joins a guessed plaintext letter to the ciphertext letter in the same crib column.
Crib placement ?
Menu graph ?
Stops and decoding
A stop is one candidate key that survived the contradiction test. The first two buttons test the selected stop. The third checks the stops currently listed. A short crib such as ATDAWN can leave many false stops.