If Bob wants to send a signed message to Alice, he may do the following:

Encrypts the message with his private key

Adds his signature "Bob" to the encrypted message

Encrypts the signed message with Alice's public key

Sends the message

a$)$ If someone other than Alice intercepts this message, what does he$/$she need to decrypt it$?$

b$)$ After Alice receives the message, and decrypts it with her private key, she sees Bob's signature. At this point, does she know that the message is really from Bob? Why?

c$)$ What does Alice need to do to make sure that the message is from Bob?

d$)$ Is it likely that someone else may have been impostering Bob even if the decrypted message is a sense making text?