Technical Details of the Enigma Machine • Hacker News Board

Re: Technical Details of the Enigma Machine

#11

Post by detaro » Sun, Jan 22, 2017, 7:46 AM UTC

SteveNuts wrote: post #8

cyberferret wrote: post #6

Like most, I always thought that the allies were desperate to get their hands on these machines during the war. I was lucky enough to get to play with one of these things when a lecturer from the Bletchley Park foundation toured here some years back. She gave a fascinating and riveting talk on the history of the device. I was surprised to hear that these were actually commercially available before the war, and that t…

I thought the commercially available models did not include the pegboard, which was crucial for the higher # of possibly combinations?

If I remember right they also used different rotors (and added more of them to swap out over time), so that's another thing to capture.

Re: Technical Details of the Enigma Machine

#12

Post by demallien » Sun, Jan 22, 2017, 9:23 AM UTC

cyberferret wrote: post #6

Like most, I always thought that the allies were desperate to get their hands on these machines during the war. I was lucky enough to get to play with one of these things when a lecturer from the Bletchley Park foundation toured here some years back. She gave a fascinating and riveting talk on the history of the device. I was surprised to hear that these were actually commercially available before the war, and that t…

Regardless, Enigma was pretty low-value intelligence. It would give you things like the daily position of u-boat packs, but generally speaking there isn't much you can do with this type of information - maybe increase the ability of your conveys to avoid U-boats, or increase slightly your ability to hunt them.

The real game was the Lorenz-stye encryptors that were used for communications between German commands. These delivered the strategic information about mid-to longterm movement of units and so on which allowed they Allies to correctly anticipate attacks. These were the messages that Colossus was used to decrypt, as opposed to the Bombes which were decrypting Enigma traffic, and which were largely derivative of earlier Polish efforts to decrypt Enigma.

I read a book a while back https://www.goodreads.com/book/show/1127838.Colossus that looks at all of this in detail. Surprisingly, if the book is correct, Turing seemed to have limited contact with the Colossus effort, and was more involved with the Enigma decryption. The Colossus people didn't seem to be terribly occupied by ideas such as Turing-completeness, they were just building machines that were capable of doing certain operations at high speed.

Re: Technical Details of the Enigma Machine

#13

Post by alblue » Sun, Jan 22, 2017, 9:40 AM UTC

There's an Enigma Machine on display in the centre of Milton Keynes this weekend https://twitter.com/alblue/status/823105879847370752, as part of the celebrations of MK's 50th anniversary. Bletchley is a suburb of Milton Keynes. http://mk50.co.uk has more if you're interested :-)

Bletchley Park has a machine on display as well, and also hosts the Bombe machine which was used to crack Enigma codes during the war. It used motors to drive copies of the rotors in Enigma in order to find a "short circuit" (where one letter coded back to itself) since this would indicate the starting point was invalid. The rotors would then tick one over and start again. The reason for so many columns was that each column of three was a different stating point - in effect, base 26 counters where each 3-digit number was started from a different number. To account for different rotor combinations and choices there were 20 or so machines built each corresponding to a different rotor choice (ABC, ABD, ABE, ACB, ACD etc). In fact it didn't just use the reflexive lookup for short circuiting; the cryptanalysts produced "cribs" which were hypothesised guesses of loops; if R-S, and S-T and T-R then this would be another short circuit option. The bombe was "programmed" with such cribs mechanically (leads plugged in to simulate connections) and then set to run. Since this process changed at midnight each day they would do the same thing day after day.

Round the corner from Bletchley Park is the National Museum of Computing http://tnmoc.org which although on the same site is a different organisation. They have the Colossus machine which was used to break the Lorenz cypher, and was the first programmable electronic computer (although the program was wired in in hardware, in effect a manual ROM).

It's well worth going to see both of these if you ever happen to be in the Milton Keynes area, or if you're passing through London - it's half an hour away by train.