Analyse Vigenère Cipher cryptosystem by using figures and mathematical formula, example

Vigenère Cipher


Below we explain Vigenère Cipher which is a Symmetric cryptosystem. We have a table including 26 characters of alphabet each associated with a number from 0 to 25.

Message (Plain-Text) we are trying to encrypt is: “Network Security”
Encryption Key that we will use for this is: “ITC”
First, we find the Numbers for the key work on the table”
ITC = 8, 19, 2

Now we need to repeat the keyword to be the same size as message text. Once that’s done, next step is to shift each character to the right based on associated key number. For example, if the character is “N”, and associated Key character is “I”, then we shift “N” on the above table, 8 cells to the right and that makes it “V”.
Note: If we reach end of the table, we go back and start from the left side.

We will do this for all message text characters in the below table:

So, as it can be seen on the above table, the output Cipher-Text would be: “VXVDGTS KGKMTQLA”