Q1) Another variation of Additive cipher uses a keyword instead of a single key. This cipher is called Vigenere cipher. Both variations work exactly the same. For details about Vigenere cipher, check textbook (Forouzan) p.g:72.
a) Encrypt the following Plaintext using Vigenere cipher:
Plaintext: stocks market is falling
Key : one
b) Is Vigenere cipher monoalphabetic or polyalphabetic? Why?