2. This problem illustrates a simple application of the CCA attack. Bob intercepts a ciphertext C intended for Alice and encrypted with Alice's public key e. Bob wants to obtain the original message M = Cd mod n. Bob chooses a random value r less than n and computes: Z re mod n tsr1 mod n Nest Bob gets Alice to authenticate (sign) X with her private key d thereby decrypting X. Alice return Y = mod n Show how Bob can use the information now available to him to determine M