Turing Bombe Simulator

The Turing Bombe Simulator Created for the Alan Turing Year 2012: A Centenary Celebration of the Life and Work of Alan Turing


Besides being highly influental in the creation of the modern computer and computer science, Turing was also working with code breaking in great secrecy during World War II.

Although kept secret for many years after the war, Turing worked with breaking the German infamous Enigma cipher at Bletchley Park just outside Milton Keynes, England.

Turing and a team of mathematicians and engineers constructed an electromechanical machine that exploited some specific weaknesses in the Enigma cipher. This machine was called "The Turing Bombe", and was based on an idea from Polish cryptographers.

We have tried to make the bombe simulator as historically correct as possible. There may of course be differences that we are unaware of.

The Simulator

Click here to access the Turing Bombe Simulator

Try it out yourself

To get an idea of what the bombe looks like in action you could download this example file: us6812_1.bmb.
Load it into the simulator and press the start button (the left of the two buttons on the front). The bombe should spring into action and finally stop with the golden indicator drums at BUO, and on the side indicate letter L.


How can I use the Turing Bombe Simulator to crack an Enigma encoded message? We get this question from time to time and since the process is somewhat complicated we decided to write a tutorial on how it can be done. Right now it is available as a PDF-file. Click on the document to the left to read the tutorial.

Many thanks to Jerry McCarthy for proofreading and for suggesting improvements!

InstructionsBrief introduction to the controls

Bombe Front

Click on a rotor bank to select it. To rotate the rotor, simply click and drag with the mouse on the large version of the selected rotor bank visible to the right. To change rotors, select a rotor bank and click on the arrow button until the desired rotor is in place. To copy a set of rotors to the whole rotor bank click the "Copy to chain" button. To copy a set of rotors to all three banks, click the "Copy to all" button

To start or stop the bombe, select the button panel on the front and click the desired button.

Bombe Left Side

This view shows the three reflector boards installed for the three rotor banks of the bombe. To change a reflector board, simply click on it until the desired board is in place.

Bombe Right Side

To the left is a miniature view of the side of the bombe. Click and drag the red rectangle to change which part is visible in the zoomed in version to the right. The buttons and lever on the right hand side are clickable. The lever is used to restart the bombe after a stop has been found.

Bombe Back

The back of the bombe contains a number of sockets. These can be connected with cables or bridge connectors. Click on an empty socket to create a cable or a bridge connector. Drag the other end of a newly created cable to the desired destination socket.

Enigma 3 and 4

There are two versions of the German Enigma machine available: the regular three rotor version and the more exotic four rotor version.

Click and hold a key on the keyboard (either with the mouse, or on your computer keyboard) to get the encrypted letter lit up in the lamp panel above the keyboard. To change key setting, click and drag on the jagged ridge of the rotor in question. To change the ring setting, open up the top cover of the Enigma by clicking on one the knobs located on the right and left sides of the keyboard. Then, while holding the SHIFT key, rotate the rotor core relative to the ring. A handy tooltip will emerge, helping you to figure out which ring setting you have.

To change rotors or reflector, open up the top cover of the Enigma and drag the desired parts to/from the rotor storage box.

Click the Enigma button a second time or the plugs at the bottom of the Enigma to access the plug board on the front of the Enigma. Connect the cables in the plug board by dragging plugs to the desired sockets.

Checking Machine

Rotate the rotors by clicking and dragging them to the desired position. To change the ring setting, hold the SHIFT key while rotating the wheel. Click the keys on the keyboard to use the machine; the corresponding encrypted letter will light up.

To change reflector, click on the reflector cartridge on the left until the desired reflector is connected. To change wheels, click on the arrow-button until the desired wheel is in place. Note that there is a yellow dummy-wheel that should be used in the leftmost position when a three rotor code is being worked on.


To save your connections on the bombe, click the Save button. All connections and settings will be saved into a file with a .bmb-extension.


To load a previously saved state of the bombe, click the Load button. Select a file that was previously saved.

Contact us if you have any comments or questions

Last updated 2015-03-25

Copyright 2012-2015 Magnus Ekhall & Fredrik Hallenberg.