this post was submitted on 25 Sep 2025
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Recently read The Code Book by Singh and it covered the Poles and Turing. It's a layman's history about cryptography and is pretty good. I found it a little simplistic, but I figure I have a better than average understanding of the field due to my interest in computers. It was published in '99, but the current day cryptography it covers is still pretty relavant.
I learned about Rejewski and his team by going down an interesting rabbit hole. I was interested in writing an Enigma machine emulator in BASIC programming language for the vintage Commodore 64 as an exercise. So I started researching how the Enigma worked to figure out how to write the code. That revealed the whole interesting history of Enigma starting as a business machine sold to companies wanting to keep their communications private when communicating with other branches.
Then the early German military interest and the Poles started looking at it. Finally Rejewski and his team, which were already doing deciphering using older methods cracking the early 3 rotor Enigma. I was shocked I had never heard about this. I had heard of Turing and even made a transatlantic journey visiting Bletchely Park (great visit if you get a chance!). I looked for everything I could learn about the Polish codebreakers and their work and found only a few sources (in English).
This first was this book which is long since out-of-print, but I found a second hand copy online. This is the best chronicle of their work I have found to-date.
Enigma How the Poles broke the Nazi code
I found a couple of other books on Engima which mostly cover the British effort, but at least give some more acknowledgement to the groundbreaking Polish effort.
Lastly, there was a movie made in 1979 that dramatize the story. It is pretty faithful to the first book I found in recounting the events. That movie is Sekret Enigma (1979). You may or may not be able to watch the entire movie right now on Youtube (with English subtitles!) here. The acting and production values were surprisingly good! I enjoyed the movie.
Lastly, if you're diving into Enigma for history or understanding, I highly recommend building your own simple Enigma machine out of paper from a PDF! Its a single PDF that can be printed on a piece of paper. You cut out strips representing the rotors and move them back and forth to see each step of out the encoding and decoding works. Note, no plugboard in this, so it truly replicates the early 3-rotor, static reflector, no plugboard, Enigma machine. Paper Enigma download and instruction site here
Unfortunately, it doesn't look like a digital version of that book has ever been released. (Other than reference text, I almost exclusively read ebooks). I did grab the documentary, sounds interesting.
Any chance you can recommend a book that covers German cryptography and the OSS effort within Germany to spy on it before and during the war?
From what I understand from diagrams and descriptions, it was a surprisingly simple device. Especially before the plugboard. I haven't tried to run the numbers or played with it, but I would think just an 8bit microcontroller could break enigma encoding in seconds or less.
When it comes to mechanical math devices, should I ever get to retire or be rich: I want to reproduce a Curta Calculator. Super neat devices.
Another similar device that I've used is the dividing or indexing head. They are used to precisely locate angled machining operations such as hobbing gears, cutting bolt heads, accurate bolt hole circles, etc.
I've had that in my bookshelf for a couple of years now, it might be time to actually read it soon...