What is authentication? How is it done?

Verifying the identity of the sender 1)The sender enters the message into the hashing program 2)The hashing program produces the message digest 3)Message digest is encrypted using senders private key and the digital signal is created 4)The signature is sent along with the message to the receiver 5)The receiver decrypts the message using the sender's public key 6)If it cannot be decrypted using a sender's public key, it has not been sent by the correct person