Breaking the Enigma code with the Turing-Welchman Bombe (Step-by-step example)

The Enigma was the most widely used German cipher machine during the Second World War. Although there were more modern and more secure encryption machines, the Enigma was quite light and transportable and was therefore suitable for use in the field.

From around 1940, the British around Alan Turing at Bletchley Park succeeded in breaking the Enigma code almost daily. However, this was not a one-off operation, but had to be carried out day after day, as the key was changed daily.

In the video, I show step by step how the code-breaking was carried out and what had to be done. Above all, I also show how the Turing-Welchman Bombe was configured, what kind of output it delivered and how the further code-breaking took place.

I use the following two simulations from VirtualColossus.co.uk:

https://bombe.virtualcolossus.co.uk/
for the Turing-Welchman Bombe

https://enigma.virtualcolossus.co.uk/
for the Enigma

0:00 Introduction
0:07 Description of the Enigma
0:23 Rotors and reflector
1:45 The plug board
2:29 Secret table with day keys
2:36 An example with two messages
3:05 Configuration of the day key in the Enigma
3:09 The rotor order
3:34 The ring positions
4:05 Plug connections on the plug board
4:39 Sending the first message (nautical weather report)
6:14 Sending the second message (strictly confidential)
6:48 The British perspective
6:59 Bletchley Park
7:18 Plaintext attack with Crib
8:28 Encryption in detail
10:08 Breaking the code from a British perspective
11:38 Breaking the plugboard by Alan Turing
13:14 The menu in the theoretical example
14:46 The Turing-Welchman bombe in action
15:18 Optimising the bombe menu
16:01 Inserting the rotors in the Turing-Welchman bombe
16:50 Menu settings on the rotors
17:33 The backside of the Turing-Welchman bombe
18:39 Wiring the bombe according to the menu
18:46 Bridge connectors
19:43 Wiring the input letter
20:55 The side switches and outputs
21:30 Output area for the found plug partner
21:39 Switching on the bombe
22:14 View into the electromechanical machine
22:58 The bombe delivers a result
23:16 Offsets of the bombe rotors
23:42 Result output of the plug partner
23:55 The checking machine (result check and determining the plug partners)
27:11 Analysing the ring positions and finding the last plug partner
28:16 Finding the right ring position
30:49 Finding the missing last connector pair
31:49 Decrypting the first message
33:32 Determining the left and centre ring positions
35:17 The day key is completely broken
35:52 Decrypting the second message