Hash-based Message Authentication Code (HMAC). HMAC provides data origin authentication, but fails to provide data confidentiality.

The following steps are performed to send a message to another user: 1. The message runs through a hashing algorithm, which generates a MAC value. 2. The MAC value is appended to the message by the sender and sent to the receiver. 3. The receiver accepts the message and adds their secret key to the message before an algorithm generates an independent MAC value for the message. 4. The receiver compares the two MAC values to see if they are the same. Which type of message authentication method is being described?