Two friends want to exchange a confidential document. It is important that eavesdroppers cannot
see this information. Furthermore the receiver should be able to validate the sender and that the
information is not altered during transport. Both friends have a public/private key combination.
Which key is used, prior to transmission, to ensure the authenticity of the document?

A.
Public key of the sender

B.
Public key of the recipient

C.
Private key of the sender

D.
Private key of the recipient

Explanation: