Your BDDCS instance is provisioned in the Oracle Cloud with SSL enabled in WebLogic Server by default. Enabling SSL for BDDCS activates WebLogic Server's default Demo Identity and Demo Trust Keystores. As their names suggest, these keystores are untrusted and meant for demo purposes only. After creating a BDDCS instance and running the provisioning wizard, you should replace them with your own certificates.
For information on WebLogic's demo keystores, see the section Configure keystores in the WebLogic's Administration Console Online Help.