Help Break Original Enigma Messages

Stereo writes "The Enigma Machine was cracked in Poland in 1932, but three messages remain unbroken, despite having been intercepted in the North Atlantic in 1942. The M4 Project, named after the four rotor Enigma M4 used for encryption, is a distributed computing effort to break them. One message has already been deciphered successfully!"

Comments

Build your own Enigma Machine

[Derling Whirvish]

Here's a site where you can order a parts kit to build you own Enigma Machine.

Java Enigma Simulator

[Derling Whirvish]

Here's a Java Enigma Simulator.

Re:Error

[Anonymous Coward]

One of the main reasons the Enigma crypts were breakable with 1940's technology is that the Germans did _not_ do useful things like that. They re-used keys, left cribs in the messages, etc.

Basically, they put too much faith in the encryption technology, and didn't put enough effort into securing the rest of the process. It's not unusual, many of today's systems have similar issues.

The comments in Bruce Schneier's blog list some more things that went wrong in the Enigma process.

Enigma is fairly close to a OTP

[jd]

The Enigma code was broken only in the trivial sense that it was possible to brute-force decrypt the messages, once the algorithm, prng and seed value were known. It was not "broken" in the purist sense of the term, in that there is no shorter method of cracking the messages other than by brute-force.

The full Enigma code is extremely difficult to break. The machine used by Alan Turing (Colossus) was massively parallel and highly optimized for the task - so much so that it is actually able to compute something like ten times as many keys per second as a modern Pentium 4 using the same algorithm. Not bad, for a machine of that era.

The Enigma suffered from numerous weaknesses - almost all of them operator error. The encryption mechanism itself was damn good and, if used correctly each time, every time, it would have been horribly difficult for the Bletchley Park team to break.

The one event that turned Enigma transparent was the re-transmission of a message without the cogs being randomized first. Because a machine had already been recovered, Turing knew what the cogs were, just not where they should be in relation to each other. By having the same message sent twice without change and without a prior reset, it was possible to overlay the two messages and thereby infer virtually everything else.

This only allows you to crack messages which use the same prng for initialization and identical cogs. Since the cogs were designed to be swappable, non-standard configurations would have been possible. These would not have been crackable - and would likely not be crackable today, if non-standard enough. (The number of arrangements you would need to test increases with the factorial of the number of ways the cogs could be designed, as well as the factorial of the number of ways the cogs could be inserted into the machine.)

The possibility exists that certain units may have used non-standard Enigma codes, but if that is the case, those codes will NOT be broken by this effort. The groups that spirited high-ranking Germans to South America and other "secure" locations must have had a communication system that the Allies had not yet deciphered, as they must have been able to operate over extremely large distances very quickly, making the use of radio a certainty.

It is also likely that some units within the German military adopted their own "extra secure" practices when using the Enigma system internally. These may or may not be crackable, depending on how paranoid the commanders were.

Enigma is fundamentally flawed.

[Convergence]

Enigma has a fatal flaw: No letter could be encyphered to itself. This is an artifact of the 'reflector disc' at the end this means that a known plaintext, or crib, can be ruled out for a particular offset, if any letter of it matches a letter in the cyphertext. This, combined with message statistics, allows for powerful cryptographic techniques to be used. These techniques were unavailable in WW2, but they exploit fundamental weaknesses in the design.

Of course, in WW2, it was the misuse of enigma that made it particularily easy to break --- It might only take one weather report to learn the daily subkey. Had Enigma been properly used, it would probably have been nearly unbreakable with WW2 era technology.

Questionable Legality

[baudbarf]

Doesn't the DMCA make it illegal to make tools for breaking encryption or even to discuss how encryption may be broken? Aren't those among us who are americans all conspiring to break federal law by attempting or discussing the possibility of attempting to break these enigma messages?

You're all terrorists. Off to Guantanamo with you.

Re:Error

[swillden]

Since the crib relied on the Enigma's inability to encode a letter to itself, the received message must have consisted entirely of the letter L.

To be precise, the message was slightly more likely to have consisted entirely of the letter L. There's no mathematical guarantee that it would contain all Ls, but a sufficiently long ciphertext message with no Ls in the output would've indicated that, with high probability, there were an unusually large number of Ls in the input. Without knowing the actual story, I'd guess that the message probably wasn't all that long, and the math would probably predict only a few more Ls than normal... but that was enough of a hint that when combined with a knowledge of human behavior gave the cryptanalysts reason to assume it was all Ls and see if they could find key settings that would produce the ciphertext from that input.

Even at the height of Bletchley Park's codebreaking efficiency, nearly every day's break came down to some clever guess of that sort... "What if we tried this?". I imagine the "all Ls" scenario was one of the easier guesses. In order to make it more certain, the codebreakers even asked the front-line forces to do apparently bizarre things, just so they'd have a keyword they could look for in the subsequent reports.

Amazing stuff...