Columnar transposition cipher decoder and encoder

In a columnar transposition cipher, the message is written in a grid of equal length rows, and then read out column by column. The columns are chosen in a scrambled order, decided by the encryption key. Since transposition ciphers doesn't affect the letter frequencies, it can be detected through frequency analysis. Like other transposition ciphers, it can be attacked by moving letters around and anagramming. Also it can be attacked using brute-force methods if the key isn't long enough.

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Columnar transposition cipher

Transposition grid




  • The columnar transposition cipher is an example of transposition cipher.
  • It is simple enough to be possible to carry out by hand.
  • It can encrypt any characters, including spaces and punctuation, but security is increased if spacing and punctuation is removed.
  • The message does not always fill up the whole transposition grid. The remaining of the transposition grid can then optionally be filled with a padding character (regular columnar transposition cipher), or left blank (irregular columnar transposition cipher).

Sample text

ltone orpol maiax ursst casip nntmt

The ciphertext above represents "columnar transposition sample txt" encrypted using the key "secret".