Sending a message and a message hash encrypted by the sender’s private key will ensure:
authenticity and integrity.
authenticity and privacy.
integrity and privacy.
privacy and nonrepudiation.
If the sender sends both a message and a message hash encrypted by its private key, then the
receiver can apply the sender’s public key to the hash and get the message hash. The receiver can
apply the hashing algorithm to the message received and generate a hash. By matching the
generated hash with the one received, the receiver is ensured that the message has been sent by
the specific sender, i.e., authenticity, and that the message has not been changed enroute.
Authenticity and privacy will beensured by first using the sender’s private key and then the
receiver’s public key to encrypt the message. Privacy and integrity can be ensured by using the
receiver’s public key to encrypt the message and sending a message hash/digest. Only
nonrepudiation can be ensured by using the sender’s private key to encrypt the message. The
sender’s public key, available to anyone, can decrypt a message; thus, it does not ensure privacy.