Flaw in the Enigma Code - Numberphile

The flaw which allowed the Allies to break the Nazi Enigma code.
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This video features Dr James Grime discussing Enigma, the Bombe and Alan Turing.

NUMBERPHILE

Videos by Brady Haran

[chaslington]

The fact that the messages were in German was top level encryption in itself.

[yungee]

I've invented an improvement on the Type X machine where a letter ALWAYS becomes itself! ;-)

[xXFluffers]

I love how the germans and british built these complex encryption machines, but the US just plopped two Navajo indians on two ends of a radio line and no one could figure out what they were saying because no one could speak Navajo, and the only way to get someone who could speak Navajo would be to kidnap a Navajo indian, lol

[skeetersorenson]

It's so sad what happened to Alan Turing after the war.

[Kredroth]

This has to be one of the simplest ways I’ve seen something so complex being explained. Great video.

[Xehemoth]

Even considering the flaw of the Enigma, it is an incredible machine even to this day. It was probably one of the most innovative machines of that time.

[Quasihamster]

"The Germans sent a weather report. It was the same every day."
-An Englishman.

[mghyy]

As used in practice, the Enigma encryption was broken from 1932 by cryptanalytic attacks from the Polish Cipher Bureau, which passed its techniques to their French and British allies in 1939. Subsequently, a dedicated decryption centre was established by the United Kingdom at Bletchley Park as part of the Ultra program for the rest of the war.

[therealzilch]

It's still a bit surprising that the engineers who developed the Enigma, a very sophisticated bit of cryptology, didn't see the flaw of not allowing a letter to represent itself, which seems pretty obvious in hindsight. But I guess people do make mistakes.

Thanks, James, for this very clear explanation. Lunch is on me if you're ever in Vienna, Hitler's favorite city.

[Bri_bees]

My mom worked in the Weather office at bletchley park. One of the keys to successful code braking was nothing to to with codes or math but hard work and filing. The ladies endlessly filled out card's, cross-referencing every operator . This allowed them to get a feel for operators who would say use there mom's name each day as a test message and give them a starting point.

[joeblow]

His explanation of the Enigma code machine is the best I've heard yet from anyone. Kudos

[davidbaird]

I absolutely love this guy, he seems so genuinely excited to tell us about this machine! His other videos are all the same way, excellent content!

[manueltrinidad]

Welp, the Enigma had a little flaw, but the worst flaw was made by te german by ending each message with the word Hitler...

[quietman]

Been to Bletchley, did the tour, read a couple of books on Alan Turing but never could get my head around the Enigma Code being a non-mathematician. Watched both the videos and now, thanks to you, I have some grasp on the complexity of the problem and how it was solved. Great videos! Many thanks.

[brianmurray]

For anybody wondering, "But wouldn't the plug board allow you to cause a letter to encrypt as itself? Imagine K after the rotors maps to U. Why not just route U to K via the plug board so that pressing K results in K (in this particular button push)?" 

Here's why not: The plug board is used both directions. So that U->K mapping on the output would also be a K->U mapping on the input. So that K you entered and hoped to get back out (to avoid this flaw) would become a U before entering the rotors. Now, to get K back as the final answer you still need to get U out of the rotors because of that U->K in the plug board. So, you're left with needing U->U coming from the rotors, which is no different than needing K->K coming from the rotors. The plug board doesn't add the ability for a letter to map to itself, and given that it won't happen in the rotors it won't happen via Enigma.

[konstanty]

Additional weakness is the Germans have very long words, which makes it easier to guess if the word fits.

[bernardpower]

The enigma code was cracked by the polish mathematician Marian Rejewski.  He showed this technique to the British and was then sidelined.  The computer to achieve the breaking of the code was designed and built (almost single handedly) by Tommy Flowers.   The breaking of enigma is largely due to these two who are rarely credited.

[theturtlepwn]

this guy is so positive and articulate and excited about math!! i've watched this video a few times now because i'm writing a paper on alan turing and it's so difficult for me to understand how he cracked enigma, but this vid is really helpful

[blipco]

The British should have called it the X-Box instead of the X-Machine, they would have made a fortune.

[jaredstearns]

It seems to me that the more messages you send encrypted, the more chances you give your opponents to crack them. Regional weather is generally not a mystery, I would think that it could be sent with much lower level of encryption, or even unencrypted. Not to mention that the forecasts were probably reasonably accurate, so you could compare the actual observed weather conditions to the encrypted message fro additional hints.