Which of the following best describes how a digital signature is created?

A.
The sender encrypts a message digest with his private key.

B.
The sender encrypts a message digest with his public key.

C.
The receiver encrypts a message digest with his private key.

D.
The receiver encrypts a message digest with his public key.

Explanation:
A: A digital signature is a hash value that has been encrypted with the sender’s private key. The act of digital signing means encrypting the message’s hash value with a private key.
If Sam wants to ensure that the message he sends to Debbie is not modified and he wants her to be sure it came only from him, he can digitally sign the message. This means that a
one-way hashing function would be run on the message, and then Sam would encrypt that hash value with his private key. When Debbie receives the message, she will perform the
hashing function on the message and come up with her own hash value. Then she will decrypt the sent hash value (digital signature) with Sam’s public key. She then compares the
two values, and if they are the same, she can be sure the message was not altered during transmission. She is also sure the message came from Sam because the value was
encrypted with his private key.
B is incorrect because if the sender encrypts the message digest with his public key, the recipient will not be able to decrypt it. The recipient would need access to the sender’s
private key, which should never happen. The private key should always be kept secret.
C is incorrect because the receiver should decrypt the message digest with the sender’s public key. The message digest is encrypted with the sender’s private key, which can only
be decrypted with the sender’s public key.
D is incorrect because the receiver should decrypt the message digest with the sender’s public key. The message digest is encrypted with the sender’s private key, which can only
be decrypted with the sender’s public key