In cryptography, a keyed-hash message authentication code (HMAC) is a specific type of messageauthentication code (MAC) involving a cryptographichash function and a secret cryptographic key. It may be used to simultaneously verify both the data integrity and the authentication of a message, as with any MAC
Sender has to encrpyt the data with its own private key, so at the receiver end he is capable to extract data using sender public key...
(B)
