The digital certificate of the Second Construction ca is the second-level builder's certificate, and the ca is only the issuing institution of the certificate, which has nothing to do with the certificate itself. Ca is a trusted third party.

Ca is the core of PKI. Ca is responsible for issuing certificates, authenticating certificates and managing issued certificates. It should formulate policies and specific steps to verify and identify the identity of users, and sign user certificates to ensure the identity of certificate holders and the ownership of public keys.