Project: lb_vigenere

The Vigenère cipher is a method of encrypting alphabetic text using a series of Caesar ciphers based on the letters of a keyword.

The objective of this project is to write a JavaScript script that implements a polyalphabetic substitution cipher that encrypts plain text strings using another string as encryption key.

The Vigenere cipher

The encryption process

The cipher uses a string called a keyword to perform multiple shifts in the alphabet during encryption.

The letters of the keyword determine the shift applied to each letter in the plaintext.

Here is how the cipher works:

1. Assign a numerical value to each letter of the alphabet. For example: 'A' = 0, 'B' = 1, ..., 'Z' = 25.

2. Repeat the keyword so that its length matches the length of the plaintext. For example, if the plaintext is racecar and the keyword is key, the full keyword should be keykeyk.

3. For each letter in the plaintext: