The Enigma Enigma: How The Enigma Machine Worked

To many, the Enigma machine is an enigma. But it’s really quite simple. The following is a step-by-step explanation of how it works, from the basics to the full machine.

Possibly the greatest dedicated cipher machine in human history the Enigma machine is a typewriter-sized machine, with keyboard included, that the Germans used to encrypt and decrypt messages during World War II. It’s also one of the machines that the Polish Cipher Bureau and those at Britain’s Bletchley Park figured out how to decipher, or break. Most recently the story of how it was broken was the topic of the movie The Imitation Game.

Let’s start with the basics.

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3DP Enigma Keyboard Improves on the Original

[Asciimation], who previously created an Enigma Machine wristwatch, decided to go all-in and make a 3D-printed Enigma machine. Not a perfect replica, but rather an improved version that works the same but doesn’t concern itself with historical accuracy. For instance, the current step involves building the keyboard. Rather than trying to re-create the spring-and-pin method of the original, he simply swapped in readily available, double-throw micro switches.

This project has a tremendous amount of fascinating detail. [Asciimation] did his research and it shows; he downloaded blueprints of the original and used hacked digital calipers to precisely measure each rotor’s teeth, so that it could be re-created for printing. He even re-created the Enigma font to ensure that his printed rotor wheels would look right–though in doing so he discovered that the original machine used one typeface for the keyboard, one for the wheels, and one for the indicator lamps.

We previously published [Asciimation]’s Enigma machine wristwatch project, where he simulated the functionality of an Enigma with an Arduino.

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Decoding Enigma Using A Neural Network

[Sam Greydanus] created a neural network that can encode and decode messages just as Enigma did. For those who don’t know, the Enigma machine was most famously used by the Germans during World War II to encrypt and decrypt messages. Give the neural network some encrypted text, called the ciphertext, along with the three-letter key that was used to encrypt the text, and the network predicts what the original text, or plaintext, was with around 96-97% accuracy.

The type of neural network he used was a Long Short Term Memory (LSTM ) network, a type of Recurrent Neural Network (RNN) that we talked about in our article covering many of the different types of neural networks developed over the years. RNNs are Turing-complete, meaning they can approximate any function. [Sam] noticed the irony in this, namely that Alan Turing both came up with the concept of Turing-completeness as well as played a big part in breaking the Enigma used in World War II.

How did [Sam] do it?

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VCF East: Enigma Machines In The Flesh

At the end of World War II, the Germans ordered all Enigma cipher machines destroyed. Around the same time, Churchill ordered all Enigma cipher machines destroyed. Add a few decades, neglect the efforts of Polish codebreakers, and make a movie about Alan Turing and an offensively historically incorrect love interest, and you have a mystique around these rare, innovative cipher machine.

At the Vintage Computer Festival East, I was privy to what is probably the largest collection of Enigma machines on the planet. The exhibit comes from [Tom] and [Dan Perera] of Enigma Museum. Right now, they’re they only place where you can go out and simply buy a real, wartime Enigma machine. The price? Well, there is a pair of million-dollar Apple I boards at VCF. The Enigmas go for about a fifth of an Apple I.

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3D Print An Enigma Machine That’s Close To The Real Thing

The Enigma machine as used by the German military during World War Two exerts a curious fascination among our community of hardware hackers and makers. Perhaps it is the mechanical complexity of the machine itself, or maybe the tale of how its encoded messages were decrypted by Allied codebreakers that contributes to this interest, but whatever it is we’ve seen a succession of Enigma-related projects over the years that shows no sign of abating.

The latest Enigma project to come our way is a particularly nice one from a group of first year students at CentraleSupélec Rennes, in Northwestern France. Their Réplique Enigma is a fully mechanical Enigma replica using 3D printing techniques, and unlike so many replicas which use modern electronics it has a set of rotors just like those you would have found in the original. The rotors themselves have a 3D-printed plastic shell which houses brass contacts and the associated writing, while the keyboard and lamp board are both made from plywood. Rather than trying to replicate the original switches from the keyboard they are using modern microswitches, however the keys themselves are upright posts that resemble the original. An AZERTY layout may not have been present on the real Enigma machines, but lends a pleasing twist to the build.

It’s worth browsing all the pages for this build, as the front page does not necessarily capture the whole build. The rotors set this Enigma apart from many of the replicas we’ve featured in the past, so you may find it interesting to take a look and make a few comparisons.

A Modern But Classic Enigma Machine

Hacking has always brought more good to the world than not hacking. The successful efforts of the Allies during World War II in deciphering the Enigma machine output still reminds us of that. Today, the machine is a classic example of cryptography and bare-metal computing.

We have covered quite a few DIY Enigma machines in the past, yet 14 years old [Andy] really impressed us with his high school science fair project, a scratch built, retro-modern Enigma machine.

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Mein Enigma

The World War II German Enigma encoding machine is something of an icon in engineering circles not just for its mechanical ingenuity but for the work of the wartime staff at Bletchley Park in decoding its messages. Without it we would not have had Colossus, the first programmable digital electronic computer, and subsequent technological developments might have taken a slower pace towards what we take for granted today.

Sadly for the Enigma enthusiast though, real machines are now few and far between. Our grandparents’ generation saw to that through the chaos and bombing of the fight across Europe. If you want to handle one you will have to either have an outrageous amount of money, work for a museum, or maybe for the GCHQ archivist.

This has not stopped our community building Enigma replicas, and the latest one to come to our attention here at Hackaday shows some promise. [lpaseen]’s meinEnigma is an electronic Enigma driven by an Arduino Nano, with rotary encoders to represent the Enigma rotors and multi-segment alphanumeric displays standing in for the lighted letters in the original. It supports all the different variations of rotors from the original in software, has a physical plugboard, and a serial port over USB through which all machine functions can be controlled. The machine as it stands is a fully working prototype, the plan is that a final machine will resemble the original as closely as possible.

All the code used in the project can be found on GitHub, along with [lpaseen]’s Arduino library for the Holtek HT16K33 keyboard/display chip used to handle those tasks.

We’ve featured a few Enigma machines on Hackaday over the years. One was built into a wristwatch, another into a hacked child’s toy, but the closest in aim to [lpaseen]’s offering is this rather attractive replica also driven by an Arduino. It is also worth mentioning that should your travels ever take you to Buckinghamshire you can visit the Bletchley Park Museum and neighboring  National Museum of Computing, to get the Enigma and Colossus story from the source.