Enigma: A Code Broken and a Revolution Started

In August of 1939, the British government set up the Government Code and Cypher School (GC&CS) on the small estate in Buckinghamshire known as Bletchley Park. It's mission: to break the codes used by the German armed forces, codenamed ULTRA. This task seemed nigh impossible due to the supreme complexity of the code-creating device known as the Enigma.

The Enigma was first patented by a German cryptologist in 1918. It was a cypher machine which used rotors to randomize letters. It was adopted by the German navy in 1926, followed soon after by the German army in 1928. However, it was the work of Polish cryptoanalysts that really expanded the general understanding of Enigmas. In fact, mere weeks before the German invasion of Poland, the Poles were able to intercept and decipher some German communiques. However, their involvement was reduced when the Germans invaded.

All was not lost, though, since some Polish scientists were able to smuggle their research on the Enigma to the British and French governments. With this information, the Allied cryptographers had a head start. However, there was still a long way to go in cracking the code of the Enigma, simply because of the sheer size of possible letter combinations.

As seen in the diagram, an Enigma has a typewriter key setup, a bank of lettered lights, and a bank of rotors. Whenever a message was to be sent through the Enigma, the two machines needed to be set up in an identical way, by sending through normally which rotors would be used (usually three out of a possible eight rotors). Next, the sender must tell the receiving end to which letter each rotor must be set (for example, rotor 1 should be at A, rotor 2 should be at M, and so on). Only when this was completed could the message be typed in on the sending end and encoded. When a key was pushed, for example A, one of the rotors would turn and a corresponding letter would light up above the keys, ( the word ANT might come out BGW). Also, when subsequent keys were pushed, a different rotor would turn almost every time, making the sheer number of possible substitutions in the billions, if not trillions. This is what the code breakers at Bletchley Park were up against.

Nevertheless, the British were prepared for the challenge, by bringing together the best minds the Allies had: chess players, crossword writers, linguists, even Egyptologists were brought in to Bletchley Park. One such individual, Alan Turing, a pioneer in the early field of computer sciences, is one of the more well known members of the ULTRA team.

There were three different and separate enigma code systems for each branch of the German armed forces: the code of the Luftwaffe (air force) was the easiest of the three. The second hardest was that of the Wehrmacht (army). The most complex of these three codes, and the one threat Bletchley Park was assigned top priority to, was that of the Kreigsmarine (navy). Their was actually a fourth code in use by the Germans specifically for the German High Command, known as FISH. The machine, known as Lorenz, used a whopping twelve rotors instead of the usual eight, and worked by intermixing the real message with random letters in between ( for example THE CAT might end up as TYRHWEFGCVAHJT), and the other Lorenz machine strips out all the unnecessary letters, revealing the real message.

The emphasis on breaking the Enigma became so great that missions were devised to raid U-Boats for their Enigmas and their code books. Also,history was made at Bletchley Park when the first programmable computer was invented for the purpose of computing all the possible combinations of the Enigma messages. In the end, it was the German's over reliance on the enigma over radio that did them in, because the analysts at Bletchley Park could compare the thousands of intercepted messages and look for the similarities.



Colossus in action



Also, it was the German's patriotism in some cases that did them in as well. the tendency for German radiomen to end messages with "Heil Hitler", or something similar, gave the analysts a base of reference for decoding the entire message. Furthermore, remember FISH, the super-complex code used by the German High Command? Interestingly enough, that code was broken in 1941 by a lazy German radioman. He was forced to send the message numerous times using the same rotor combination setup, and he even abbreviated parts of the message at times. This was all the masterminds needed to 'filet' FISH.

The real impact of the ULTRA program was not only the hastening of the end of the war, but also, with the advent of the Colossus computer, it paved the way for the computer revolution into the future, and for this we are eternally grateful. Until next time, take care, and thank you.