Is X.509 an industry standard or an industry solution? X.509 public key certificate. In the X.509 scheme, the default encryption system is public key cryptosystem.

For identity authentication, X.509 standard and public key encryption system provide a digital signature scheme. Users can generate a message and its summary (fingerprint). The user encrypts the abstract with the private key to form a signature, and the receiver decrypts the signature with the sender's public key, and compares it with the received information. Fingerprints? Compare them to determine their authenticity.