vCenter Single Sign-On is an authentication broker and security token exchange. When a user is authenticated with vCenter Single Sign-On, that user can access all installed vCenter services to which the user has been granted access. Because traffic is encrypted for all communications and only authenticated users can be granted access, your environment is secure.
Install or upgrade vCenter Single Sign-On before you install or upgrade any other vSphere components. See the vSphere Installation and Setup or the vSphere Upgrade documentation.
For information on replacing certificates for services that use vCenter Single Sign-On, see vSphere Security Certificates and Encryption.