Noob Question about ENIGMA
in [Cryptography]
|
From: biject on 20 Nov 2009 23:24 On Nov 20, 3:17 pm, "Don Phillipson" <e...(a)SPAMBLOCK.ncf.ca> wrote: > "Felix Reuthner" <s...(a)reuthner.net> wrote in message > > news:he1vt7$5tk$1(a)online.de... > > > . . . How did the code-breakers identify the correctly > > decrypted text among the zillions of garbled attempts? Did they have the > > possibility to check for sequences that usually appeared in a > > transmission? > > Methods included: > 1. Brute force (all possible combinations), facilitated by > the "bombes" (programmable electro-mechanical machines.) > 2. Exclusion of negative possibilities: e.g. most ciphers include > (Rule A) that no letter P may be enciphered as itself = P > (Rule B) that no reciprocal Q=R may occur elsewhere as R=Q > These two rules function negatively in any deciphering programme: > i.e. any setting which permits non-A or non-B can be skipped as > a wrong setting: and brute force methods may usefully winnow > out and discard such non-rule keys. > 3. Enemy breaches of good cipher practice, e.g. replicating > standard terminology in short routine messages (such as > weather reports), e.g. using the same word or the same > number of nonsense characters as filler material to pad > out a message to standard length. > > For details see only recent books such as: > Sebag-Montefiore, Enigma: the Battle for the Code (2000) > Simon Singh, The Code Book (1999) > Calvocoressi, Top Secret Ultra (1985) > Earlier books (e.g. by Kahn, Lewin, Winterbotham) do not > really answer your question (i.e. were perhaps censored.) > > -- > Don Phillipson > Carlsbad Springs > (Ottawa, Canada) I guess one could view at least in some versions of the ENIGMA as a very long keyed cipher with a very short block. The block size being that of a single character log(26)/log(20) around 5 bits. This made it very easy to attack by only looking at the start of message Does anyone know the Unicity Distance in Characters for the different versions of the ENIGMA. Since among others things since the ENIGMA is such a short block and easily attacked using only a ciphertext only attack mode. How much harder if the message where first encrypted with standard enigma then do a bijective BWT followed by another enigma pass. This would effectively make the whole message a single block. Unlike the original ENIGMA if the first letter A the output could be A. Also if two messages identical except for a singe character in mddle of the input most likely the outputs will be totally different again unlike ENIGMA. How much harder would it be to attack this in a ciphertext only attack. David A. Scott -- My Crypto code http://bijective.dogma.net/crypto/scott19u.zip http://www.jim.com/jamesd/Kong/scott19u.zip old version My Compression code http://bijective.dogma.net/ **TO EMAIL ME drop the roman "five" ** Disclaimer:I am in no way responsible for any of the statements made in the above text. For all I know I might be drugged. As a famous person once said "any cryptograhic system is only as strong as its weakest link"
From: Mok-Kong Shen on 20 Dec 2009 17:17
Artie Choke wrote: [snip] > Lots more here: > http://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma A number of books are available from Bletchley Park Shop: http://www.bletchleypark.org.uk/shop/index.rhtm/130825/cat.html |