When a user needs to provide message integrity, what options may be best?

A.
Send a digital signature of the message to the recipient

B.
Encrypt the message with a symmetric algorithm and send it

C.
Encrypt the message with a private key so the recipient can decrypt with the corresponding public key

D.
Create a checksum, append it to the message, encrypt the message, then send to recipient

Explanation:
D: The use of a simple error detecting code, checksum, or frame check sequence is often used along with symmetric key cryptography for message integrity. A is pointless, without sending the message itself to compare hash results. B has a weakness if the attacker ever gets the symmetric key used to encrypt the message. C, while providing privacy, is, by itself, computationally inefficient relative to the objective of message integrity. Page 360.