Prompt that there is no SSL public key, indicating that there is something wrong with the CA certificate and it needs to be replaced. The digital certificate is issued to the server by the authoritative CA(CertificateAuthority) organization, and the CA organization generates the certificate through the relevant information provided by the server.

When the client initiates a request, the server sends the digital certificate to the client, and the client decrypts the encrypted ciphertext through the public key provided by CA to obtain a hash value (digital signature). At the same time, the content of the certificate is hashed with the same hash algorithm to get another hash value, and the two hash values are compared. If they are equal, the proof is ok.