Monoalphabetic Substitution Cipher Techniques

  Monoalphabetic Substitution Cipher, also known as a simple substitution cipher, relies (depends) on a fixed replacement structure. That is substitution is fixed for each letter of the alphabet. 

A simple example is where each letter is encrypted as the next letter in the alphabet: "a simple message" becomes "B TJNQMF NFTTBHF". Each letter can be encrypted to any symbol [&,%,?,/,*,{},@,~,+,-] not just another letter.

1.) Additive Cipher

The Simplest Monoalphabetic cipher is an Additive cipher.

This cipher is sometimes called Shift Cipher.

When the Cipher is Additive, the Plain Text, Cipher Text and key are integers in Z(26).

For Encryption: C = (p + k) mod 26

For Decryption: P = (c - k) mod 26

Where, C = Cipher Text

                  P = Plain Text

                  k = Key 

The secret key between Alice and Bob is also an integer value.

The encryption Algorithm adds the key to the Plain text character.

Decryption Algorithm Subtract the key from the ciphertext character.

Encryption

Decryption

2.) Atbash Cipher is a Monoalphabetic Substitution Cipher that was initially used to Encrypt the message using the Hebrew Alphabet.

Atbash Cipher uses a specific key where the letters of the alphabet are reversed. For example, the letter “A” is replaced with the letter “Z”, the letter “B” is replaced with “Y” and the pattern continues.

HOW TO SOLVE ATBASH CIPHER?

Basically, ATBASH Cipher reverses the alphabet to create Cipher Text.

HOW TO ENCRYPT USING ATBASH CIPHER?

Once you have generated the Cipher Text alphabet, encryption is very easy. You need to replace each Plain Text letter with the corresponding Cipher Text letter in the table.

Video Link: https://youtu.be/PnVcFE93kUY

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