Code 4 : Keyword Cipher

Keyword Cipher

The Keyword cipher is identical to the Caesar Cipher with the exception that the substitution alphabet used can be represented with a keyword.

To create a substitution alphabet from a keyword, you first write down the alphabet. Below this you write down the keyword (omitting duplicate letters) followed by the remaining unused letters of the alphabet.

ABCDEFGHIJKLMNOPQRSTUVWXYZ
KEYWORDABCFGHIJLMNPQSTUVXZ

To encipher a plaintext message, you convert all letters from the top row to their correspondng letter on the bottom row (A to K, B to E, etc).

These types of simple substitution ciphers can be easily cracked by using frequency analysis and some educated guessing.

Source : http://www.braingle.com , http://www.secretcodebreaker.com, http://substitution.webmasters.sk/simple-substitution-cipher.php

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