Mal's Post

"Probably the most well known cipher of all time is the German Enigma of World War II. German military and diplomatic information was encoded using an typewriter style machine called “Enigma.” This device had three wheels which would type a different letter than the one you choose on the keyboard. To further complicate the encryption, after each character, the wheels would change so that a different letter would be produced for repeated characters. This made the classic style of decryption and code breaking impossible to complete on an Enigma created document."

So. my understanding of Enigma is this. to decrypt a code, the receiver has to know which wheel to use and where to start on the wheel. Apparently this created a barrier during the war for the enemies. England deciphered the code, but kept it secret until like 30 years ago.

I don't know exactly how this is related to what we've been doing in number theory. Probably something to do with the probability that it would encrypt a letter for another letter given several wheels.