The HCP for cloud scale system requires certificates to communicate securely with external systems.
For the HCP for cloud scale system to communicate with Identity Providers (IdPs), storage components that use SSL-protected communication, and external encryption key management systems, the system must accept the certificate from those clients. Your system prompts you to accept a client certificate when testing the connection to an IdP using the System Management application. It's best to use valid SSL certificates trusted by a certificate authority, but you can also upload client certificates manually.