How did the Enigma Machine work? (2021) [video]

The National Cryptologic Museum is well worth visiting for the Enigma Machines alone. It's free to get in, right next to NSA headquarters, but you don't need a visitors pass or to go through a guard station. When I was there they had ~4 Enigma Machines available to look at.

> but you still couldn't plain brute force an encrypted message today

The analysis you link to shows that it has about 76-bits of keystate based on the most generous analysis for the 3 of 5 rotor machines. This should be within the range of a motivated nation-state attacker using custom hardware to just outright brute force.

Even if you don't know the plaintext, you can do a quasi plaintext attack where you just try every long enough word in the dictionary at every non-prohibited location and apply the classic attack-- and I expect this would still be much faster than a brute force search while only having extremely limited assumptions about the plaintext.

Thanks!

I think it's worth giving a mention of https://en.wikipedia.org/wiki/Code_talker as well. (The Allies were not sure if their encryption was secure, and attempted to find other means of securing their comms.)

The reflector ensures that's not possible. There are 26 independent circuits that go from the key switch through the pegboard through the rotors and to the reflector.

Pressing a key makes one of those 26 circuits hot. Now attach the reflector: it necessarily connects that hot circuit to a different one.

The rotor is "per se" designed to never let this happen. The combination from the beginning to traverse all 3 switches is 1:1, so unless the reflector connects to itself, it will never actually collide. Or let's put it differently. Imagine just 1 switch, as it's the same reasoning. It will always change the letter, and will never return the same letter, given that the first switch always follows the key you are pressing.

> took artistic license with the story

This is an understatement. It was well enough as a movie, but I think you will come away with a worse understanding of Turing and Bletchley Park than if you had never watched it. I cannot say enough about how it mischaracterized Turing's work, his personality, the nature of the codebreaking endeavors, or the contribution of others.

(Gross oversimplification but..) One seemingly innocuous bug deep in the encryption "library", that no letter could map to itself, plus a bit of social "engineering" in taking advantage of the fact that messages often included the same text (e.g. "heil hitler") often in the same position, with a smattering of German complacency and arrogance assuming that their machine was uncrackable.

Pretty funny that the lessons learned here are still relevant to this day.

The German assumption, throughout the war, was that Enigma could be cracked but it was probably too hard so the Allies would not try. You can see that not all of the German Military was as easily sold on this belief, because some forces stayed with a relatively basic machine while at the end the U-Boats were using a four rotor machine and much stricter rules to reduce attack surface. Ironically they were undone by their need to transmit and receive very succinct messages in order to spend less time on the surface where they were vulnerable.

Germany was in particular unaware that Poland - understandably nervous of an increasingly combative Germany years before the war started - had cracked Enigma when it was a commercial system in the 1930s. This knowledge was transmitted to the British in 1939, and the cryptanalytic team who did it began leaving Warsaw before (inevitably) Germany invaded in September.

There's a small memorial to the Polish code breakers at Bletchley Park, it's not exactly on the main tour, so if you care ask someone when you're there to tell you where. People who were there suggest it made maybe 12 months difference, specifically to Enigma (Bletchley Park did other less famous cryptographic work) which is a pretty significant difference.

Enigma is interesting because it's so famous and yet it's completely the wrong design, and this is exactly the era when people stop doing that. The Colossus computer, also at Bletchley park, is to break the Lorenz cipher not Enigma, because Lorenz is a much more "normal" design to us today. It's a Vernam stream cipher, it encrypts bit streams and it merely so happens that those bit streams are Morse code. You could perhaps say Lorenz is a (distant) ancestor of, say, ChaCha20.

In contrast Enigma looks like cryptography from previous centuries, it encrypts symbols, one symbol in -> one encrypted symbol out. No letter on your Engima machine's keyboard representing the symbol you wanted? Say it in words or don't encrypt it. This is in some ways more practical (Enigma was actually used with radio traffic, but in principle you could send letters, or encrypt your diary, or whatever) but in cryptographic terms it's a complete nightmare.

Even after it was "broken", it took a lot of work to decrypt - sometimes allies were months the German messages.

Watch his Apollo mission videos.

I love Jared Owen. He’s so damn good at explaining how stuff works.

It reminds me of my grandpa always taking time to explain how things worked by taking it apart and showing me what the insides looked like. Things like his transistor radio, table fan, etc.

Branch Education is another channel that does this brilliantly: https://www.youtube.com/c/BranchEducation/videos