Firstly, the message is hashed, then the hash digest is encrypted with its own private key, and the encrypted content and the original message are sent to the receiver.

After receiving the content, the receiver decrypts the encrypted hash digest with the sender's public key to obtain the plaintext of the hash digest, and then uses the same hash algorithm to obtain the hash digest of the original message sent. Matching the obtained hash digest with the decrypted hash digest. If they are the same, it proves that they are sent by the sender; Otherwise, the sender will not send them.