vSphere 6 makes managing SSL certificates a lot easier than previous releases. It ships with its own Certificate Authority, (VMCA) that issues certificates for all components on your behalf, rather than having to replace each service certificate manually, or relying on self-signed certificates. This new VMCA comes with the Platform Services Controller (PSC) that can be installed as a separate appliance, or embedded within the vCenter Server installation or Appliance.
By default, the VMCA will self-sign its own certificate to be used as a CA certificate that will sign all requests for certificates. This self-signed CA certificate can be replaced by a certificate that is signed by a 3rd party root CA or your own root CA. Any certificate signed by the VMCA, which is an intermediate CA to your root CA, can then be validated by clients with the root CA and VMCA certificates installed.