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.