Protecting the confidentiality of a message is accomplished by encrypting the message with the following:

A.
Sender’s private key

B.
Recipient’s public key

C.
Sender’s public key

D.
Recipient’s private key

Explanation:
To achieve both authentication and confidentiality, the sender should include the recipient’s name in the
message, sign it using his private key, and then encrypt both the message and the signature using the
recipient’s public key.