Kaid's Blog

Columnar Transposition Cipher 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 ciphertext. 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. Example  The key for the columnar transposition cipher is a keyword e.g.  GERMAN . The row length that is used is the same as the length of the keyword. To encrypt a piece of text, e.g. defend the east wall of the castle we write it out in a special way in a number of rows (the keyword here is  GERMAN ): G E R M A N d e f e n d t h e e a s t w a l l o f t h e c a s t l e x x In the above example, the plaintext has been padded so that ...