Simple Substitution Ciphers

The Simple Substitution Ciphers - A short introduction

Cipher systems are used to encrypt a plain text in to a secret text called cipher text. The aim of using a cipher system is to avoid accidental/intentional intercepting of the message by a third party.

The simple substitution cipher works for this purpose. It's one of the most used cipher system for manual encryption. The idea is to substitute an alphabet or character with a randomnly selected character.

For ex:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Z X C V B N M Q W E R T Y U I O P A S D F G H J K L

Here, as you can see, the first row is the list of English alphabets in the strict order.
The row beneath is the randomnly selected character set. No rules may be assumed to select the substitution character set. ( The underneath row.)

The encryption and decryption is comparitively easy. For encrypting a Plain text into the Secret text, one just need to substitute the character from the second row

For Example, if we want to encrypt the plain message of ENGLAND,
E's substitution is B
N's substitution is U.
Similary, G= M, L = T, A = Z, N = U, D = V.

So, ENGLAND will be written as B U M T Z N V.

The key strenght of Simple Substitution cipher is equivalent to the sum of 26 ways the alphabets can be arranged. ie; 26 * 25 * 23 ......... 4*3*2*1.
ie; 26! ==> 403,291,461,126,605,635,584,000,000.

So, this type of cipher system has a great key strength..

Here, the key management will be a problem. Since, the same key is used for encryption and decryption.