Was Enigma really that hard to crack, given that you had access to hundreds of messages per network per day?

Question

Well, I guess that I have always been a little bit suspicious ... so to speak ... of the "official stories" about the difficulty of recovering Enigma message texts during WW2, because it seems to me that they're always focused on recovering "one message, in isolation." Whereas, the actual situation faced by the intercept stations is that they were every day flooded with messages ... all of them encrypted using exactly the same (of course, unknown) network-key settings, differing only by their per-message keys.

So – my question is: "did all of that 'daily network-key mumbo-jumbo' actually matter," if you could be assured of a sufficient number of messages each day which ultimately differed from one another only by a three- or four-letter wheel setting?

I could go on at some length, but I think the question is clear: could not cryptanalysts have exploited the process of statistically comparing the gathered messages against each other, treating most of the machine as simply "a pair-swapping transposition table that didn't change?"

Answer 1

Yes, it's just that the messages were often low value.

There was nothing like gps back then, you would not get a real time location of a submarine. At best you'd get a lat/long which is precise to several km and then spend hours trying to get a plane there.

You'd get vague obvious warnings like "Germans may be attacking this convoy"- and there was no central directions, it was up to the uboat commander to decide the details .

But that was important enough that the government gave them a few people to help them crack these messages.

So given such a small, resource poor team was allocated to the task it was a big accomplishment.

Answer 2

Yes and no. With today's computer resources, you'd be able to crack it in less than a day, by brute forcing it. Also, with today's cryptanalylis we'd be able to intelligently crack enigma - and they would have been able to do it back then, if they had the man power. I suggest that you visit Bletchley Park, where the enigma was cracked. They explain the cryptanalylis of the enigma there, and the full story, with the Nitty gritty.

Answer 3

Enigma was mostly broken by guessing clear text, applying some clever maths, and brute forcing which settings led to the encrypted text.

The trick was that they could crack the settings by using some message where the message itself had no value whatsoever, but that could be guessed. An extreme case was weather reports that were sent to different locations using in some case easily crackable encryption, and in another case using Enigma encryption. The message content was known, and would have been known by just looking at the sky because it was just a weather report, but could lead to crack the daily settings.

The really important messages were handled much more carefully and wouldn't have been crackable using these methods.

"treating most of the machine as simply "a pair-swapping transposition table that didn't change?" wouldn't have worked, because the transposition table changed after every single letter :-) And remember, they didn't have today's computers.