Consider the following protocol that involves both RSA public-key operations and DES. Suppose that A has an RSA private key prv(A) and an RSA public key pub(A). Suppose that B has an RSA private key prv(B) and an RSA public key pub(B). Assume both A and B knows each others public key. A wants to send B some message M. A selects random DES key K and send B the following two messages:

-- E_pub(B)( K, Sig_prv(A)(K)) -- E_K(M)

"E" means encryption and "Sig" means digital signature. Which of the following statement(s) is true? Briefly explain why or why not. (A) Only B can decipher the contents of the message M (B) B is certain that the message M is from A (C) B can prove to a third party that the message M arrived from A.