Explain how to break a character substitution cipher

Answer:

Initially we are provided with a string of characters known as plain text and a number know as key.

• Firstly we will transform the given characters with the corresponding numbers in the alphabet.
• Now we will perform addition i.e., for encryption we use E(P) = (p+k)mod 26, for decryption we use D(C) = ( p- k) mod 26 , where p = plain text, c = cipher text, k = key.
• Finally obtained Plain text number or cipher text number we will convert it into Characters.