Talk:Straddling checkerboard
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The example given of adding a number and then going backwards seems to have a flaw.
Consider if "62" came up after the non-carry addition. When you tried to go back to letters, what would you do? There's no letter you can put down for this.
InlovewithGod (talk) 14:59, 21 August 2008 (UTC)
Fixed. I added in a forward slash, sometimes used to signify a change from letters to numbers and back again, for 6-2 so that you can always go backwards now.
InlovewithGod (talk) 13:04, 25 August 2008 (UTC)
Actually, I believe that empty box was supposed to be a space... There is still a problem that means you can't always go backwards. What if the end of the string was "06"? You'd get an E, and then not know what to do with the 6. This can trivially be caused by changing the key in the article from 0452 to 0451. 82.33.61.156 (talk) 13:12, 10 June 2009 (UTC)
merge
editI suggest merging the "straddling checkerboard" section of the VIC cipher article into this straddling checkerboard article, leaving behind a very brief Wikipedia:Summary style summary of and link to the "straddling checkerboard" article. --68.0.124.33 (talk) 15:16, 10 August 2009 (UTC)
Oops
editThe edit on 00:48, 3 February 2010, from User 72.95.65.182, was actually me. I thought I was logged in but I wasn't. Sorry! --Doctorhook (talk) 00:53, 3 February 2010 (UTC)
Refactoring
editI've split this out from the VIC Cipher. As the VIC Cipher page needs a re-write (which I plan to do). However (the VIC Cipher) is complex enough without needing to explain the Straddling Checkerboard. As the Straddling Checkerboard is a cryptographic entity in its own right (historically and mechanically) to the VIC Cipher it should have its own page Zasmkl (talk) 13:41, 12 January 2020 (UTC)
Fractionation ?
editI don't think the term "fractionation" in connection with a straddled cipher is very illuminating or purposeful. It is much more important to understand the term "reading frame" in relation to the effect of straddling. Using the example of the genetic code, it should be made clear what effects straddling has on the usual, predictable reading frame of the cipher steps. The aim of straddling is not to fractionate polygrams, but to make cipher step boundaries unpredictable. Since an unauthorised decryptor can no longer determine where the last cipher step ends and the next one begins with the straddling checkerboard, cryptanalysis is considerably more difficult, especially if the straddling procedure is carried out polyalphabetically with a large number of straddling checkerboards. There is a Wikipedia article on the "reading frame (genetics)", but none on the "reading frame (cryptology)". It should also be mentioned that straddled ciphers can only be used without problems in error-free communication channels. If errors occur, straddled ciphers quickly become an indecipherable jumble of letters. As in genetics, the reasons for this are reading frame ("frame shift") mutations due to "insertions" and "deletions", as well as incorrectly transferred letters or characters ("point mutations").
Fractionation is achieved by spatially separating the individual characters of a polygram (this works quite well with a column transposition with keyword, for example (e.g. in the ADFG(V)X cipher)). However, this is not the case here: the characters of the polygrams remain together, there is no transposition and therefore no fractionation. However, this does not mean that a subsequent columnar transposition does not make the encryption even more secure. Because then, in addition to the cancellation of the reading frame, existing bigrams are also fractionated.
The coding shown in the next discussion article (once with numbers, once with letters as well as / and .) can be subjected to a columnar transposition with a mnemonic word or phrase. In the former case, the transposition key "THEUSUALSUSPECTS" produces :
ØØ32Ø 19188 Ø2159 37332 7Ø553 42226 71211 69642 96723 Ø6246 1Ø158 Ø4165 89172 2Ø2Ø7 8Ø273 3897Ø 34652 17179 43445 5Ø832 43Ø11 213Ø6 38972 92Ø25 22227 Ø6225 Ø516Ø Ø1255 252Ø2 1596Ø 1Ø214 74211 14ØØØ 29517 82598 Ø1767 72598 26253 19412 222Ø5 66Ø1
In the latter case, however, you get :
ZNTON ETNE. LOENS SARLF AAUEE TNRRT DESNR SRNLG EETSS RNEOE SRNYS STSNT RRTOE INNIE EMAER ONRET ORSEN SASBE TOOZA EIRIS OTIZT TNNEI MARNR SNORT AERNU NIENR MOANI VEINE IOANR KAONY NIIMI NTRTA SEBRO R.UTE ESTER HENO Permissiveactionlink (talk) 18:49, 16 July 2025 (UTC)
Ciphertext size
edit"Compression: The more common characters are encoded by only one character, instead of two; this reduces the ciphertext size and potentially the cipher's proneness to a frequency attack.".
If you encrypt only the (152) letters of this short text (without punctuation and word spaces !) with the straddling checkerboard shown in the text, you get the following ciphertext consisting only of (204) digits :
21429 6Ø7Ø9 98451 25Ø29 47Ø21 42929 45212 53732 11Ø79 37ØØ5 21422 Ø222Ø 67452 86745 Ø2125 37321 1Ø785 91Ø32 24231 65412 5897Ø 22632 1Ø912 5Ø218 6Ø25Ø 71Ø66 19868 Ø3522 6Ø41Ø 51832 82867 125Ø2 186Ø2 5Ø796 Ø745Ø 5Ø991 43237 Ø6163 Ø5216 73113 2127
The digits appear in the following numbers : Ø (29x, 14,2%), 1 (28x, 13,7%), 2 (41x, 20,1%), 3 (15x, 7,4%), 4 (13x, 6,4%), 5 (20x, 9,8%), 6 (16x, 7,8%), 7 (17x, 8,3%), 8 (11x, 5,4%), 9 (14x, 6,9%)
The digits are NOT equally distributed in the ciphertext. Frequency analyses will not get you any further here. The digit 2 occurs most frequently, although it does NOT encode any of the eight most common characters in English in the straddling checkerboard used ! Instead, you have to concentrate on the most frequent bigrams and trigrams in the (English) language: th, he, an, in, er, re etc. as well as: the, ing, and, ion, tío, ent, ere etc. Of course, the most common words are also important for cryptanalysis: the, of, and, to, a, in, that, it, is, I, etc. For example, the ciphertext in 203 bigrams contains the group 125 (th) FOUR TIMES, and the group 25Ø (he) a further FIVE TIMES. And in 202 trigrams the group 125Ø (the) occurs THREE TIMES.
The proportion of the eight most common letters (E,T,A,O,N,R,I,S) in standard English-language texts is 64.32%. This means that when such texts are encrypted with a straddling checkerboard, they always result in a ciphertext consisting of digits that is about 1/3 longer than the original plaintext. This applies quite precisely for the example to (204/152) * 100% = 134.2%.
A ciphertext extended for 34 % relative to the plain text does not necessarily have to be created. You can also super-encipher the digit worm with a cyclically repeated keyword consisting of digits modulo 10, and super-encipher the result with the straddling checkerboard back into letters or . , / :
With the digit keyword "362145798Ø237" you then get the first super-encipherment :
57633 17689 11187 46476 35Ø44 1554Ø 8Ø9ØØ 55ØØ5 73114 Ø68Ø7 58784 16799 47689 12959 59ØØ5 5ØØ57 31132 89Ø55 97852 ØØ1ØØ 5Ø243 84777 89714 8757Ø 74729 51293 45Ø72 5Ø4Ø2 83146 72289 7Ø88Ø 85123 5339Ø 52Ø69 69595 29793 7Ø599 1Ø632 85443 Ø9327 7815
This ciphertext consisting of digits is then converted back into characters (A - Z, . , /) using the straddling checkerboard, which means that it is again super-enciphered.
NRUAT RZSTT TIROV RUNEO OTNNO EIESE ENNEE NRATT OEZER NIRIO TYSSO RZSTM NSNSE ENNEE NRATT ALSEN NSRIN BETEE NEGAI ORRRI SRTOI RNRER ORMNT MAONE RHEOE LATOY DISRE IIEIN TFNAA SENB. .NSNM RSARE NSSTE ULNOO AESAK RITN
179 characters. More than the original 152 plaintext characters, but shorter than the original ciphertext with 204 digits.If the plain text length is n, then the length of the superenciphered ciphertext c is 2/3 n <= c <= 4/3 n. Permissiveactionlink (talk) 11:06, 17 July 2025 (UTC)