The Enigma Machine and Ultra Intel

During the Second World War, the Germans possessed a tool that gave them a huge advantage over the Allied forces: the Enigma Machine. Although it was available commercially, its biggest adopters were the German Military. It allowed them to encrypt and decrypt communications much to the frustration of their enemies. Once the Allied forces figured out how to break the cipher, the messages they decrypted became known as Ultra intelligence.

Mechanics of the Machine

The machine had several steps to its encryption. The first was a simple substitution cipher. To do this the machine contained 3 rotors (later more). The rotors had the letters A to Z on them. Pressing the "B" button might result in an "R" being printed, and pressing the "R" button would result in a "B". This was a very rudimentary and very easy to break. The real strength came from the rotor advancement feature. When a letter was pressed, the neighboring rotors would be advanced a certain number of spaces depending on what key was pushed previously. This meant that the substitutions changed every time a key was pressed, and the substitution was dependent on the letter before it.

The plugboard added a second level of complexity. Looking like a vintage switchboard, there were 26 sockets and accompanying wires. The operator would plug the wires into the appropriate sockets using instructions that changed everyday. The sockets were labeled A to Z, and would (for example) redirect a push of the "F" button to be a push of the "L" button before it reached the rotors, and vice versa. This allowed up to 13 pairs to be swapped at anytime.

Like most ciphers, a starting position had to be set for the rotors. The machine allowed the operator to set the starting position for the 3 rotors that were indicated with the letters A to Z. This starting position was typically changed everyday.  To enhance this, a key was set for each message that was comprised of another 3 letters. These were chosen by random by the operator and were different for each message. The operator would set the machine to the starting position then type the 3 letter key. Then the operator would change the starting position to the key they had chosen for the message, and continue typing the actual message. Once of the biggest weaknesses came when operators got lazy and used easy to guess keys.

Breaking The Code

The Germans knew that the Enigma was theoretically breakable but concluded the amount of effort needed to brute force the cipher (brute force means to try every combination until the correct one is found) was too high to be practical in application. However, the Polish had great reason to solve the riddle. Under more threat from the Germans than anyone else, the Polish Cipher Bureau undertook the task of "breaking" the machine years before war broke out knowing the advantage they would gain.

Their biggest breakthrough came in 1932 when a French military intelligence agent passed along documents relating to the enigma. They provided a brief overview of how the machine worked, and complete instructions on how to use it. With this information the Poles were able to build a basic machine and begin deciphering German transmissions. The process was still not completely fool proof, but substantial amounts of communication could be deciphered relatively quickly.

Much to credit to the machine itself, the biggest breakthroughs in deciphering the messages was gained from errors made by the German operators, not the machine itself.  Once the working's of the machine were still known, someone still needed to know the 3 letter key used to encode the message. Fortunately for the Allies, the operators frequently got lazy and used things such as "AAA" or "BBB", or used a series of letters that appeared next to each other on the keyboard. When it came to figuring out the keys, the Pole's relied on an oversight by the Germans. Almost all messages started with the passage "ANX" which was German for "To" followed by "X" used as a spacer. Knowing this, cryptographers could try various combinations of keys until they produced an output matching this, instead of having to decrypt several more letters to determine if the resulting word was actual German. This greatly sped up their efforts.

Once the war was underway, the Poles provided their knowledge on breaking the Enigma to the French and British who until then had been unable to decipher Enigma encoded communications. Shortly after, the Germans went from using 3 rotors in the machine, up to 5 to 8 rotors. They would still only use 3 of the rotors on a given day, but knowing which ones to use complicated the key. Solving this was a job of more traditional information gathering methods. The first of the new Enigma machines to be captured was one found on the U-Boat U-33, along with instruction manuals and codes. Two days later, the U-110 was captured with another machine and codes. Several more machines were captured from the German Navy, which allowed the Allied forces to decipher messages for quite some time.

Ultra Intelligence

Once the Allied forces were able to break the Enigma messages, they referred to the results as Ultra Intelligence. The name is derived from the fact that at the time, the most sensitive information was classified as Most Secret, but decoded Enigma messages were considered even more sensitive than this, and were called Ultra Secret. This was shortened later to just Ultra.

Although the Ultra information gave a great advantage to Allied forces, they had to be careful upon acing on it. There were concerns that unlikely encounters or attacks would make the Germans suspicious of the Enigma's strength. To combat this, scout planes were often sent out and deliberately spotted by the Germans so that the Allied forces would have a cover story after attacking. The Americans were reportedly more brazen about acting on Ultra information, and this strained relations between them and the more conservative British.

Almost all Enigma encoded messages could be broken within a couple of days by 1945. After the capture of German cryptographic personnel, American forces learned that although the Nazi's were aware it could be broken, they did not believe the Allied forces had the time or resources to do it.

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