Top 5 Features of an Enigma | Bletchley Park

During World War Two most military communications were sent via radio, but the enemy could listen in on those radio signals.

In order to keep messages secret from the enemy you had to encipher them. Cipher machines like the Enigma were used by the German army and air force during the war to protect their radio messages.

Join our Research Officer, Dr Thomas Cheetham, as he explores in-depth the top 5 features of one of the most common Enigma machines of World War Two, the Enigma I.

Credits
Archive image(s) of Codebreakers at Bletchley Park © Crown Copyright. Reproduced by kind permission, Director GCHQ

Animation(s) of Enigma circuit path and exploded rotor view © Courtesy of Jared Owen

Image(s) of German Heer (Army) Enigma being used in the field, General Heinz Guderian standing © Courtesy of The National Cryptologic Museum

About Bletchley Park - Bletchley Park is a vibrant heritage attraction and museum, open daily to visitors. It was the home of British World War Two codebreaking; a place where technological innovation and human endeavour came together to make ground-breaking achievements that have helped shape the world we live in today.

This unique site was previously a vast Victorian estate, where parts including the Mansion still survive, expanding during wartime to accommodate Codebreakers Huts and Blocks. During World War Two, the Government Code and Cypher School (GC&CS), now known as the Government Communications Headquarters (GCHQ), was based at Bletchley Park.

It grew from a small team of specialists to a vast intelligence factory of thousands of dedicated women and men. This extraordinary combination of brilliant and determined people and cutting-edge technology contributed significantly to Allied victory. In tough conditions, they provided vital intelligence and developed pioneering technological innovation that had a direct and profound influence on the outcome of the war.

The site continues to reveal secrets and tell fascinating stories of our national legacy. The Bletchley Park Trust - Bletchley Park Trust is a registered charity, heritage attraction and independent museum. As an independent charity, we rely on income from our visitors, Friends and supporters to secure the long-term future of the site.

Registered charity number: 1012743

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[privateprivate]

By far the best video on this machine that I have seen, great job!

[davidcreagh]

Going to BP is on my bucket list when and if I go to England. I have seen many demos of Enigma and looked at a real one but this is by far the most detailed.

[randylplampin]

Your audio quality is parsecs ahead of the previous "Five Weaknesses." Excellent!

[mcfontaine]

Another brilliant explanation from Thomas.

[celestialskye]

It's absolutely dizzying 🥴 my admiration to all the men and women that worked to crack this monster 😮🤨🤯🧐👏👏👏👏👏

[CharlesShopsin]

Great video! I'm looking forward to the rest of the series.

[Zerbey]

76-bit encryption, that really puts it into context how clever this machine was. Up until the 1990s it was common to only use 40-bit, which was trivial to break. These days we use 128 or 256.

[thorns]

Regardless of how you set up the plugboard, it is still only a simple substitution cipher.

It has nothing to do with pairs.

The main problems for the Enigma is that you solve them in order, first you get the wheel order and wheel settings using a number of Bomb machine equivalents. The rotor combinations do require brute forces, but you only need about 1000 12-wheel machines to do a full parallel brute force search on that part.

Each of these machines figure out the ring setting using current for parallell processing (back in the early 2000s when Enigma code breaking details were first release, you could run the program that simulates the Bomb at approximately the same speed as the real machine, so about 10-15 minutes to find a possible ring setting, which was read out and checked).

Once you have the ring setting, you have a message in German that is encrypted using a substitution cipher, with several known substitutions because of the cribs.

And this is there the pairing comes in, as you get a free substitution with each one you have.

[scottsmith]

Two suggestions for future videos:
How trivial would it be to solve Enigma with today's computers?
With the benefit of hindsight, what could Bletchley Park have done to solve Enigma faster?

[thorns]

I believe there were special variants that had a printer instead of the light board, and that printer could be place in another room. That way the operator(s) never saw the decrypted message.

[bwhog]

I thought some Enigma machines had four active rotors. Seems like the Germans could have kept the plug board much like it was but use thin and thick connectors on single wires to allow for more flexibility on the plug board. Color them differently and specify which color should go on which row and it shouldn't be terribly hard to keep straight. As you say, there are procedural things that could have been done to give better results, but you also have to tie that with field conditions for am army on the move and subject to bombardment at any time. Also, seems to me that any sensible operator should go through the trouble of decrypting the first couple of words following encryption to make sure the machine was operating correctly.

[gowdsake]

I always wonder why everyone says current when it is voltage !

[alexmarshall]

At 1 minute 12 seconds you press the P key 4 times and this lights A, J, U, U, ... is this correct that U is encrypted twice from pressing P👉🇬🇧👈

[jonss]

Why did Station X not detect amything regarding the German intention to execute the attack that became the 'Battle of the Bulge'?

[danielwitt]

According to the Tom Stoppard film you had to find at least 17 linked letters then plug it into the Colossus. Most probably rubbish

[joezephyr]

There are twenty six letters and ten numbers for a total of 36. But no character can come out as itself. Therefore the odds of guessing any character are 1/35. No matter the complexity it is still 1/35