Assignment:
In this assignment you will create a program that can ask the user to input a code word and then use that word to encrypt a given message using the Vigenère cypher. The Vigenère cypher uses a code word to scramble a plain-text message into an encrypted message. Generally, only alphabet characters are encrypted, and non-letters are normally removed. For our purposes, we will simply copy punctuation and spaces from the plain-text to the cyphertext - only the letters will be encrypted. Upper-case letters are encrypted to upper-case and lower-case to lower-case. To perform the encryption on some text, each letter in the text is matched with a letter in the secret code. The letter in the secret code determine the offset applied to corresponding letter in the plain-text. Each code letter produces an offset, for example "A" represents an offset of 0, "B" an offset of 1, "C" an offset of 2 and so on. A letter in plain-text, say "m" is encrypted by a code letter of "A" to "m", by "B" to "n", by "C" to "o" and so on. The encryption that offsets a letter past "z" wraps back around to start with "a".