The imitation game is a great movie about Alan Turing. It is rare to attend a movie any more where people spontaneously clap at the end.  I have some experience in cryptology working for the NSA, so I found the movie very interesting. I thought it might be interesting to note some of the “gaps” in the story.   It is based on a true story, and most of the story line is somewhat true. However the real story is far more complex and involved a lot more people.

The first “bomba” was designed by Polish cryptographer Marian Rejewski. It actually worked well, until the Germans adopted a plug board which made things more complicated. Alan Turing actually used this “bomba” to design his machine which he called a “bombe.” It was a great achievement and he deserves a lot of credit for his invention, but the movie makes this far too simplistic.  One was led to believe that Turning’s great machine magically broke all the Enigma codes in about 20 minutes each day after figuring that Germans liked to say Heil Hitler.  I hope no one believes real life cryptographers are that stupid. If that was true, cryptographers would have been on it in a New York minute.

The entire project was called Ultra. Defeating Enigma was a daily battle and in many ways the real vulnerability was with sloppiness by operators rather than the system itself. It was the humans who provided the keys to breaking the code. For example an operator might realize than the same message had been sent on two different cyber networks, sometimes in different codes. Or an operator might notice that a German operator always started his messages the same way.

In addition sometimes protocols designed to reduce risk have the opposite impact. German procedures did not allow using the same rotor in the same slot as it had been in the preceding configuration.  They also didn’t allow the machine to ever reproduce the original letter struck.  This actually helped cryptographers because it limited the number of options.

The bombe designed by Turing did not “break” the code.  It reduced the potential outcomes to a manageable number. Then cryptanalysts would compile a menu when was then used to break the code.  If you watch the movie Enigma it does a better job of explaining how this works.

It is a fascinating movie and without a doubt the cryptographic team at Bletchley Park was material in winning the war for the allies. The breaking of the Enigma code was a magnificent achievement that can never be discounted.  Alan Turing was a fascinating man who clearly played a major role in this achievement, but he didn’t exactly win the war by himself. He also was an admitted homosexual but no one ever accused him of being a spy.  Sadly, the story is accurate with regard to how homosexuals were treated in 1952.

By the way, Turing wasn’t very good at crossword puzzles. It is true that British intelligence did put crossword puzzles in newspapers as a means of recruiting cryptographers. It is also true that at times British intelligence had vital information from Ultra but didn’t use it because they feared tipping Germany off to the vulnerability of the Enigma code.  Those kinds of decisions were not made by Alan Turing or any other cryptographer.  They were made by Winston Churchill.

Great move about a real life miracle.

TDM