By default, which keyring is used to authenticate a ProxySG to other devices?

The correct answer identifies the "Appliance-key" as the keyring used by default to authenticate a ProxySG to other devices. The Appliance-key plays a crucial role in securing communications between the ProxySG appliance and other network components, such as other proxy services or connected devices. It is specifically designed for the operational integrity of the device itself, ensuring that any service dependencies or inter-device communications remain secure.

Using the Appliance-key by default simplifies the authentication process, allowing administrators to set up and manage their network more efficiently. This key is fundamental because it provides a secure method of verifying the identity of the ProxySG among the devices in the system.

Understanding the purpose of different keyrings helps clarify why the Appliance-key is designated for this role, as it directly relates to the administrative functions and security protocols within a ProxySG environment. In contrast, the other options, such as User-key, Service-key, and System-key, serve different purposes or may not be used specifically for authenticating the ProxySG appliance itself.