all the questions should be fairly easy. So please so them all or at least half of them.

1. Use the Euclidean algorithm to compute 7-1 in Zso or explain why no such value exists. 2. The ciphertext CRWWZ was encrypted with an affine cipher. We know that the plantext starts with HA. Decrypt the message. 3. Using MAMA as the key for a Vigenre cipher, encrypt BE COOL. What is the minimum block-length of this cipher? 4. The ciphertext YIFZMA was encrypted by a Hill cipher with matrix 1 3 the plaintext. 5. How many keys are there for each of the following ciphers? (a) Shift ciphers (b) Affine ciphers (c) General substitution ciphers (d) Vigenre ciphers where the keyword has length 3