Vigen$$re Cipher

The Vigen$$re cipher is a method of encrypting alphabetic text

using a series of interwoven Caesar ciphers, based on letters

of a keyword.

Notice how in a caesar cipher, you shifted the alphabet by

some integer value. Consider a mapping that maps

alphabetic letters into numbers $($and vice versa$)$

The main difference between a Vigen$$re cipher and the

Caesar cipher, is that the Vigen$$re cipher changes the shift

value for every character, depending on a key.

Example of a Vigen$$re Cipher

Consider the following

But how did we get from the plaintext to the ciphertext?

But how did we get from the plaintext to the ciphertext?