As always, these posts are meant to be quick birds-eye views of topics. Some things may be glossed over in favor of saving time reading. This article will be cross-posted to my personal blog located at: ping-sec.com, Let’s begin!
During World War II, there was a massive effort to decipher the Nazi communications secured by a mysterious device known as the Enigma Machine. It was a state-of-the-art electro-mechanical device used by the Nazis to encrypt their communications. Alan Turing and his colleagues at Bletchley Park are credited with saving countless lives and likely reducing the length of the war overall through their work. Turing and Co. created a device extremely similar to the Enigma, named the Bombe. The Bombe and the Enigma both used the following: Rotors, Plugboards, Reflectors and Daily Key Settings. Here are some further details:
Rotors: The core component of the Enigma were its rotors. These were disks with electrical contacts on each side. Each rotor could then be set to one of twenty-six positions, corresponding to a letter of the alphabet. When a key was pressed, the rotors would rotate and change the electrical pathways which influenced the letter substitution.
Next was the Plugboard (Steckerbrett in German).
This added another layer of complexity by allowing pairs of letters to be swapped before and after the electrical signal passed through the rotors. This would significantly increase the number of potential encryption settings.
Following the journey through the rotors and the plugboard, came the Reflector. The reflector sent the electrical signal back through the rotors in an entirely different pathway. This allowed the same machine settings to be used for both encryption and decryption.
Finally, Daily Key Settings would tie all this together. The security of the Enigma relied on the daily key settings, which included things such as rotor order, rotor starting positions and plugboard connections. These settings were changed daily and both sender and receiver needed to use the same settings to communicate properly.
Bletchley Park were not the only organization working on cracking Enigma. The effort started much earlier with the Polish Cipher Bureau in the 1930’s. Below is an image of a 1930’s era Military Model Enigma I.
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Sooner than later, the Polish were outpaced as the Nazi’s increased the machine’s complexity. This left a talented group of cryptanalysts to break the advanced encryption and provide unprecedented access to Nazi communications. Their efforts gave the Allies strategic advantages in several battles and campaigns.
A rebuilt Bombe machine from The National Museum of Computing at Bletchley Park.
Bombe from the rear depicting the cable management:
In the end, one of the discoveries made by the team at Bletchley Park was that the Nazi’s transmitted a daily weather report and signed off in the same manner each time with the same phrase. Something so boring, mundane and simple became a boon to the Allies and their code breaking research. This over-used proclamation praising their leader allowed the team to finally crack the Enigma Machine and its encryption.