Tool to decrypt / encrypt with a transposition in columns. Column transposition encryption, also called column permutations, is a cryptographic technique that modifies the order of the letters of a previously written text in a table.

Columnar Transposition Cipher - dCode

Tag(s) : Transposition Cipher

dCode is free and its tools are a valuable help in games, maths, geocaching, puzzles and problems to solve every day!

A suggestion ? a feedback ? a bug ? an idea ? *Write to dCode*!

Column transposition encryption writes plaintext in a rectangular array of N columns (inline fill) with N the size of the permutation key.

__Example:__ The text COLUMNS is encrypted with the permutation 1,3,2 of the key word COL, it is written in the table

Columns | 1,2,3 | Permuted cols | 1,3,2 |

Plaintext | C,O,L | Ciphertext | C,L,O |

U,M,N | U,N,M | ||

S,X,X | S,X,X |

Fill in the empty boxes with a neutral letter (like X).

The encrypted message is then read in columns

__Example:__ CUSLNXOMX

It is possible to read line by line, in which case the encrypted message would be CLOUNMSXX

Decryption by Columnar Transposition is similar to encryption. The difference lies in the writing in the table (in rown or in column according to the reading method used during the encryption), as well as in the order of the columns which are permuted before being sorted again in ascending order.

__Example:__ A permutation 1,3,2 was used to obtain the message CUSLNXOMX (reading by columns):

Permuted cols | 1,3,2 | Sorted cols | 1,2,3 |

Ciphertext | C,L,O | Plaintext | C,O,L |

U,N,M | U,M,N | ||

S,X,X | S,X,X |

The message consists of the transposed / swapped letters, so it has all the letters of the original message but in a different order.

The coincidence index after transposition of columns is unchanged from that of the plain text language.

For short permutations (up to 5-6 letters), a brute-force algorithm can test all permutations.

Otherwise, by knowing a word of the plain text (if possible with unusual letters), it is possible to find the position of its letters and to deduce the compatible columns permutations.

dCode retains ownership of the online 'Columnar Transposition Cipher' tool source code. Except explicit open source licence (indicated CC / Creative Commons / free), any 'Columnar Transposition Cipher' algorithm, applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or any 'Columnar Transposition Cipher' function (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) and no data download, script, copy-paste, or API access for 'Columnar Transposition Cipher' will be for free, same for offline use on PC, tablet, iPhone or Android ! dCode is free and online.

Please, check our dCode Discord community for help requests!

NB: for encrypted messages, test our automatic cipher identifier!

transposition,column,columnar,permutation,disorder,grid,table,rectangle,rectangular

Source : https://www.dcode.fr/columnar-transposition-cipher

© 2021 dCode — The ultimate 'toolkit' to solve every games / riddles / geocaching / CTF.

Feedback

▲
Thanks to your feedback and relevant comments, dCode has developed the best 'Columnar Transposition Cipher' tool, so feel free to write! Thank you!