don@allegra.UUCP (Don Mitchell) (05/08/85)
Actually, the German "enigma" code was not broken in the complete sense in WWII. The Germans put the key into the message in a stupid way. The method Reeds used to break crypt is a relatively new idea; probably discovered around 1960 by the NSA. The government still used rotor machines up until then.
reeds@alice.UUCP (Jim Reeds) (05/08/85)
>From allegra!don Wed Dec 31 19:00:00 1969 > >Actually, the German "enigma" code was not broken in the complete sense >in WWII. The Germans put the key into the message in a stupid way. >The method Reeds used to break crypt is a relatively new idea; probably >discovered around 1960 by the NSA. The government still used rotor >machines up until then. > Flattering but false. I used old ideas, well explained (for example) in H. F. Gaines's book. Although the paper does not say it, the crypt(1) command is really not an "enigma" cipher, but something simpler. A simple transformation of the cipher text turns the output of crypt(1) into a "sliderule" type cipher with (unknown) mixed ciphertext component and unmixed pt component with known key sequence. Recovery of the mixed component is straightforward. The alphabet size makes it harder, the self inverse nature of the CT component makes it easier. These ideas occurred to several people at the same time. I just rushed into C code first. Jim Reeds.