Which of the following options is right PKI The sequence description of the work process is correct?

1. PKI Entity direction CA ask CA Certificate. .

2. PKI Entity received CA After the certificate, install CA Certificate.

3. CA receive PKI Entity CA When requesting a certificate, add your own CA Certificate reply to PKI entity.

4. PKI Entity direction CA Send a certificate registration request message.

5. PKI When the entities communicate with each other, they need to obtain and install the local certificate of the opposite entity.

6. PKI Entity received CA The certificate information sent.

7. PKI After the entity installs the local certificate of the opposite entity,Verify the validity of the local certificate of the peer entity. When the certificate is valid,PC The public key of the certificate is used for encrypted communication between entities.

8. CA receive PKI The entity's certificate registration request message.