Double Columnar Transposition Cipher Decoder and Encoder

The double transposition cipher is considered one of the most secure ciphers that can be performed by hand. It is equivalent to using two columnar transposition ciphers, with same or different keys. During World War I and II, it was used by various agents and military forces.

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Double Transposition Cipher Tool

You must enter the message.

Knowing the encryption key

You must enter the encryption key.

Not knowing the key

Options


Not seeing the correct result? Try Auto Decode or use the Cipher Identifier Tool.


Key Text

Still not seeing the correct result? Then try experimenting with the Auto Decode settings or use the Cipher Identifier Tool.


Grid


            

Features

  • The double transposition cipher is an example of transposition cipher.
  • Until the VIC cipher, the double transposition cipher was considered as the most complicated cipher that an agent could operate reliably 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, or left blank.
  • If the same key is used for encrypting multiple messages of the same length, they can be compared and attacked using a method called "multiple anagramming", finding solutions to both.

Sample Double Columnar Transposition Cipher Text

Code-breaking is not only fun, but also a very good exercise for your brain and cognitive skills. Why don’t you try breaking this example cipher:

smosm pdame lmnno sgale edait taoel eifes knpwa nhrdd taldr srwhe nthct ednth inosa oeole ideen elehe hewiu dtewr cosdx dseic ethil t