Implements a program that encrypts messages using Vigenère’s cipher.

$ ./vigenere ABC
plaintext:  HELLO
ciphertext: HFNLP

NOTE: If keyword is single letter 'A' or 'B', etc.., than it encrypts just like Caesar's cipher.

Usage

Your program should behave per the examples below. Assumed that the underlined text is what some user has typed.

$ ./vigenere 13
Usage: ./vigenere k

$ ./vigenere
Usage: ./vigenere k

$ ./vigenere bacon and eggs
Usage: ./vigenere k

$ ./vigenere bacon
plaintext: Meet me at the park at eleven am
ciphertext: Negh zf av huf pcfx bt gzrwep oz

For more info: docs