6. (10 points) Suppose you receive a digital certificate that contains M and [h(M)lCA where M- (Alice, Alice's public key) and "CA" is a certificate authority. (a) How do you verify the signature? Be precise (b) Before you verify the signature, what do you know about the identity of the sender of the certificate? (c) Assuming that you trust the CA, after verifying the signature on the certif cate, what do you then know about the identity of the sender of the certificate