“I cannot forecast to you the action of Russia. It is a riddle wrapped in a mystery inside an enigma.” – Winston Churchill (1939)
Perhaps this post will only appeal to byronius who, along with me, is a student of the World Wars of the 20th century. If this is the case, I offer my apologies in advance. But if you like secrets and how to steal them, then by all means read on!…
(BTW: I commented on this in Cat-eyes’ What’s that up in the sky? post, but decided the subject merited its own post.)
But this remarkable story isn’t about weapons or strategy or bloodshed (at least not directly), but about codes and ciphers. From the clever way the British intercepted a German diplomatic cable message (the Zimmerman Telegram) in 1917, decoded it and (realising its importance), funnelled it (wiped discreetly of British fingerprints) to Washington, forcing a reluctant America into WWI… on through the famous (and devilishly clever) German ‘Enigma’ machine and the Japanese ‘Purple’ and JN-25 ciphers.
The urgent (even existential) requirement for the Brits as WWII loomed to break the German Enigma cipher drove the formation of ‘Station X’, better known as ‘Bletchley Park’, tucked away on an estate in the pleasant English countryside of Buckinghamshire… The men and women at Bletchley DID succeed, and brilliantly; at the very least shortening the war by about two years and perhaps even preventing England from losing the war in the dark days when England stood alone against Hitler before America’s entry into the conflict.
Oh and BTW, Alan Turing and Tommy Flowers also designed and built the very first digital computers at Bletchley Park to speed their decoding efforts.
If you like puzzles, Enigma was a real humdinger, and one might forgive the Germans for believing it was ‘unbreakable’ with roughly 3 x 10114 (courtesy NSA) possible combinations (rotors+plugboard+start positions). Factorials get big fast! Enigma was self-decoding. If a cipher output is fed back into the machine (or one set up exactly like it), the original plain text is retrieved. A ‘reflector’ disk essentially reverses the encoding process. Pretty damn slick. Just to make sure, an operator had ‘extra’ pre-wired rotors to choose from (8 was typical later in the war)… so 3 rotors were chosen ‘randomly’ and inserted in ‘random’ order and set to a ‘random’ starting position. A 3-letter ‘random’ initiator sequence started each message. Adm. Karl Dönitz, the Kriegsmarine (German navy) commander requested (and got) a 4-rotor version of Enigma after he started losing more U-boats in the North Atlantic than he thought could be put down to chance. But the method still seemed completely foolproof… and the Germans (to their grief) believed in it utterly.
I emphasised the ‘random’ factor in setting up an Enigma machine for operation. This was Enigma’s weakness that the Bletchley teams recognised and exploited. I could do a whole post on the nature of ‘randomness’ alone, but here it suffices to say that if you use truly ‘random’ choices for setting the machine, it IS pretty much ‘unbreakable’. However, human beings are NOT capable of producing random sequences. Neither are computers. Such numbers are called ‘pseudo’-random for a REASON. Truly random sequences are surprisingly difficult to produce. If you need truly random numbers, monitoring radioactive decay is the easiest way to go.
Any cipher system also suffers from repetition in messages. The Germans blew it here as well. Overconfidence in Enigma (and a lack of understanding in coding basics) led many Enigma operators to end messages with flourishes such as ‘Down with England’ or ‘Heil Hitler’, and initiator sequences were often a girlfriend’s initials or similar repeated sequences. Major error. Failure to ‘randomise’ the rotor starting positions properly also aided the code breakers.
Fortunately for us, these operator blunders allowed Bletchley Park to detect PATTERNS. And even better, German arrogance (and British sneakiness) kept them from EVER snapping to the fact that their cipher system had been fatally compromised.
A 3-rotor Enigma machine in operation (1943)
The surviving German high-command were shocked white and speechless when informed after the war that Bletchley Park had been reading their most intimate ‘mail’ through almost the whole war!
I can’t leave this subject without a nod (and a wink) to my Dad (USN Lt. Roy Howard [code name: 'Hot Pants' ? ;-}]), who spent a good part of his naval career working on just these sorts of problems in the late 1940's-early 50's. As far as I know (not too far I'll admit), neither US diplomatic nor military operational ciphers have EVER been broken in the modern era. Our guys are pretty damn good. Dad could probably reveal further details, but of course then he'd have to kill me...
However, this should remind us that NSA certainly has capabilities (some of which Cat-eyes wrote about some time back in Big Brother is here) that most American citizens would (and should!) be pretty uncomfortable about... There are two sides to every coin... Just sayin'.
Finally, if you'd like to play with a virtual Enigma machine, here's a fun Enigma simulator.