In a digitally-signed message transmission using a hash function,

A.
The message digest is encrypted in the public key of the sender.

B.
The message digest is encrypted in the private key of the sender.

C.
The message is encrypted in the private key of the sender.

D.
The message is encrypted in the public key of the sender.

Explanation:
The hash function generates a message
digest. The message digest is encrypted with the private key of the
sender. Thus, if the message can be opened with the sender’s public
key that is known to all, the message must have come from the
sender. The message is not encrypted with the public key because the
message is usually longer than the message digest and would take
more computing resources to encrypt and decrypt. Because the message
digest uniquely characterizes the message, it can be used to verify
the identity of the sender.
Answers “The message digest is encrypted in the public key of the sender” and “The message is
encrypted in the public key of the sender” will not work because a message encrypted in the public
key of the sender can only be read by using the private key of
the sender. Because the sender is the only one who knows this key, no
one else can read the message.
Answer “The message is encrypted in the private key of the sender” is incorrect because the
message
is not encrypted, but the message digest is encrypted.