A Vigenère cipher uses a sequence of "shift-by-n" simple substitutions, where the shifts are indexed using a keyword, with "A" representing a shift-by-0, "B" representing a shift-by-l, etc. For example, if the keyword is "DOG," then the first letter is encrypted using a simple substitution with a shift-by-3, the second letter is encrypted using a shift-by-14, the third letter is encrypted using a shift-by-6, and the pattern is repeated—the fourth letter is encrypted using a shift-by-3, the fifth letter is encrypted using a shift-by-14, and so on. Cryptanalyze the following ciphertext, i.e., determine the plaintext and the key. This particular message was encrypted using a Vigenère cipher with a 3-letter English keyword.
Required:
Find plaintext and the key.
