6. Alice wants to deliver a large random number M to Bob. Assuming x is what is being sent over the channel, specify if the confidentiality and/or integrity of the message has been preserved in the following cases. Explain the associated decryption and verification processes. Assume that Alice and Bob share the key k; Alice and Bob have public and private key pairs (pka, skA) and (pkb, skb) respectively. (a) r= EX(M) (b) x = Ep (M) (c) x = M || H(M) (d) x = EX(M) || H(M)