Bombe

Tap it to search for the Enigma setting. Type a message to break in the Splash tab.

The Bombe was the codebreaking machine of Bletchley Park in England. Alan Turing designed it in 1939, building on a Polish machine, and Gordon Welchman added the diagonal board that made it far faster. Its rows of drums copy Enigma rotors. From a crib, a few words the codebreakers guessed were in a message, it tried rotor settings at great speed and stopped when the logic held. About 200 were built, run day and night mostly by members of the Women's Royal Naval Service, the Wrens.

Tap it: the drums spin through the settings, stop, and the lamp lights; then the message reads out. Simplified here: the plugboard is taken as known, and the drums turn far slower than the real ones.

The splash really searches rotor starts using its Enigma calculation and stops at the first matching crib. It assumes the plugboard is known and supplies the message itself. It illustrates a search, rather than reproducing the historical Bombe’s menu and diagonal-board logic.

1. Correct

   Turing’s 1939 design and Welchman’s diagonal board contributed to the British Bombe.¹

   The About attribution and approximate count of 200 machines are supported; the museum gives 202 established machines and predominantly Wrens as operators.

2. Correct

   The splash tests rotor starting positions against a crib.²³

   An independent implementation agrees with the first matching setting and decrypted output for four messages, including a one-letter ambiguous crib.

3. Simplified

   The splash simplifies the historical search.³

   It knows the plugs and derives a crib of up to 12 letters from the supplied plaintext. It has no menu loops or diagonal-board deductions for unknown plugs.

4. Simplified

   A crib match is not proof of a unique original key.³

   The enumeration stops at the first matching start. Short cribs can match several settings, even when the shown plaintext is recovered.

1. 1Bombe historical background, The National Museum of Computing; John Jackson
2. 2How Enigma works, Crypto Museum
3. 3British Bombe, Crypto Museum

Simplified

The plaintext is used to generate a ciphertext and its crib. Only fixed I–II–III, rings AAA, and known plugs AR GK OX are searched. It enumerates 17,576 starts and accepts the first crib match, which need not identify a unique key. Drum movement is a slowed animation rather than the search’s mechanical timing.

Made in Splashery. Its code is MIT.

This link opens it in the Playground. To put it on your own page, add the element and one script tag. Every option.