Film Club w/c 4 Apr 2025 - Enigma (2001 film)

A reminder of this week's film, if you want to watch it.

I watched it at the weekend and found it very interesting. It made me research the Enigma machine and how they decrypted the messages. 

If you don't know, the messages were encrypted using a substitution cypher (substituting one letter for another) Trying to put it as simply as possible, the Enigma machine changed each letter entered so if the operator entered the word  "SUPPORT" the machine might create "VXSSRUW" to replace that word in the encrypted message. So to decrypt the message, all the V's had to be changed to S, all the X's to U, all the S's to P, all the R's to O, all the U's to R, and the W's to T.

To make it more difficult, the machines were reset daily (the German operators were given a daily code book) To have a chance of deciphering a message, the Allies needed to be able to guess what some of the words might be, for example some messages were weather forecasts and they could guess what some of the words would be in those forecasts and then once they knew some of the substitution letters they could work out other messages. This was called having a crib. 

In the film they showed a room full of panels with rotating wheels, which looked to me like a prototype computer. I looked it up and this machine was called a Bombe - it helped decipher encrypted messages by allowing multiple Enigma settings to be quickly checked.

Here's a fun Enigma quiz: Can you decrypt the following encrypted message?

Here's the crib - the letters follow the same substitution pattern as "SUPPORT" above, and it is about the NAS:

WKH QDV VXSSRUWV  DXWLVWLF SHRSOH

Nobody seems to have worked out my encrypted message above, so here's the answer - the message is: THE NAS SUPPORTS AUTISTIC PEOPLE

I used a pattern to make up my encryption, and each letter of the cipher was the 3 letters on in the alphabet from the letter in the original message. So T became W, H became K, E became H, and so on. 

Of course the Enigma machines didn't use a pattern when replacing letters for a cipher, the substitutions were random and the code changed every 24 hours, plus the messages were in German so the Bletchley Park staff had to have a knowledge of that language too. It just shows how difficult the job was for them!

Nobody seems to have worked out my encrypted message above, so here's the answer - the message is: THE NAS SUPPORTS AUTISTIC PEOPLE

I used a pattern to make up my encryption, and each letter of the cipher was the 3 letters on in the alphabet from the letter in the original message. So T became W, H became K, E became H, and so on. 

Of course the Enigma machines didn't use a pattern when replacing letters for a cipher, the substitutions were random and the code changed every 24 hours, plus the messages were in German so the Bletchley Park staff had to have a knowledge of that language too. It just shows how difficult the job was for them!