BY J.STEPHY GRAFFIIMSC(C.S)

1.Inroduction2.What is a columnar transposition?

3. Methods of Transposition

4.Colunmar transposition ciphers

5.Double transposition

6.Conclusion

Introduction •The columnar transposition cipher is a fairly simple, easy to implement cipher. It is a transposition cipher that follows a simple rule for mixing up the characters in the plaintext to form the cipher text.•Although weak on its own, it can be combined with other ciphers, such as a substitution cipher, the combination of which can be more difficult to break than either cipher on it's own. The ADFGVX cipher uses a columnar transposition to greatly improve its security.

What is a columnar transposition?

A columnar transposition, also known as a row-column transpose, is a very simple cipher to perform by hand. First, you write your message in columns. Then, you just rearrange the columns. For example. I have the message, "Which wristwatches are Swiss wristwatches." You convert everything to upper case and write it without spaces. When you write it down, make sure to put it into columns and number them

  Unencoded Rearranged

Column #:

4 2 5 3 1W H I C HW R I S TW A T C HE S A R ES W I S SW R I S TW A T C HE S

1 2 3 4 5H H C W IT R S W IH A C W TE S R E AS W S S IT R S W IH A C W T  S   E

•Now, you just read the columns down in the order that you number them. Above, you will see the key is 4 2 5 3 1, which means you write down the last column first, then the second, then the fourth, the first, and finally the middle. When you are all done, you will get "HTHESTHHRASWRASCSCRSSCWWWESWWEIITAIIT". I can put the example's information into the encoder for you: Encode or Decode

Methods of Transposition•Using a key word or phrase, such as CONVENIENCE, assign a number to each letter in the word using this rule: the numbers are assigned starting with 1, and they are assigned first by alphabetical order, and second, where the same letter appears twice, by position in the word.

•Then, write in the message under the keyword, writing across - but take out columns, in numerical order, reading down

C O N V E N I E N C E 1 10 7 11 3 8 6 4 9 2 5 --------------------------------- H E R E I S A S E C R E T M E S S A G E E N C I P H E R E D B Y T R A N S P O S I T I O Nproduces HEESPNI RR SSEES EIY A SCBT EMGEPN ANDI CT RTAHSO IEERO

Grid numbering:

1 2 3 4 5 16 11 6 1 6 7 8 9 10 17 12 7 2 11 12 13 14 15 18 13 8 3 16 17 18 19 20 19 14 9 4 5 10 15 20 X 20 15 10 5 4 9 14 19 20 19 18 17 16 3 8 13 18 15 14 13 12 11 2 7 12 17 10 9 8 7 6 1 6 11 16 5 4 3 2 1

Layout: O - - O - O - - - 1 416 - - O - - - - - O 8 5 2 - O - - - - O - - 12 6 13 - - O - O - - O - 18 20 7 9 - - - - X - O - O 8X 15 5 - - - O - - - O - 19 9 17 O - - - - O - - - 3 1014 - O - - O - - - O 7 10 11 6 - - O - - - - - - 11

(encrypting with a turni)

third position: t e h n i N c - - - - - - O - - G s r G y R i O - - - O - - O - s p I t a L - - - O - - - - O i L m e E n s – O - - - O - - - T O g s a w g O - O - . - - - - i P e R t O t – O - - O - O - - h h V a a I t - - O - - - - O - D t u i E r a O - - - - - O - - n m T H i I - - - O - O - - O (ng grille to provide thi)

( illustrative example)

to produce the encrypted result:TESHN INCIG LSRGY LRIUS PITSA TLILMREENS AITOG SIAWG IPVER TOTEH HVAEAXITDT IAIME RANPM TLHIE I

Columnar transposition ciphers

A columnar transposition cipher is a simple hobbyist cipher in which the order of the letters in a message are changed, but the letters themselves are left unchanged.        The cipher is performed by writing the message into a grid, and then taking the letters out in a different order. The letters are written into the grid straight across the rows. Here we have written THIS IS A SAMPLE MESSAGE into a 5-column grid.  

•A transposition cipher encodes a message by reordering the plaintext in some definite way. Mathematically, it can be described as applying some sort of bijective function. The receiver decodes the message using the reordering in the opposite way, setting the ordering right again. Mathematically this means using the inverse function of the original encoding function.

Double transposition•A single columnar transposition could be attacked by guessing possible column lengths, writing the message out in its columns (but in the wrong order, as the key is not yet known), and then looking for possible anagrams. Thus to make it stronger, a double transposition was often used. This is simply a columnar transposition applied twice, with two different keys of different (preferably relatively prime) length. Double transposition was generally regarded as the most complicated cipher that an agent could operate reliably under difficult field conditions. It was in actual use at least as late as World War II (e.g. poem code).

Conclusion

•Transposition can be used to generate a scrambled order of the letters in the alphabet for use as a substitution alphabet.•Transposition forms part of a fractionation cipher, where letters are divided into parts, then the parts are put back together in a different order, belonging to different letters.