4. (a) In a public-key encryption using RSA, you intercept the ciphertext C-10 sent to a user whose public key is e-5, n-35. What is the plaintext M? (You must show Extended Euclidean steps) (10 points) (b) In a Diffie-Hellman scheme, common prime p=7 and a primitive root ?-3 (10 points) 1. If user A has public key YA-6, what is A's private key XA? 2. If user B has public key YB-5, what is the shared secrete K