What is the role of subordinate or intermediate CAs (Certificate Authorities) in a hierarchical certificate model?

Subordinate or intermediate Certificate Authorities (CAs) play a crucial role in a hierarchical certificate model by issuing certificates to users, tailored with different certificate policies for various purposes. This delegation of responsibilities helps enhance security and scalability within the public key infrastructure (PKI).

In a PKI framework, the root CA is at the top of the hierarchy, responsible for the creation and management of subordinate CAs. These intermediate CAs can issue certificates not just to end users but also to other intermediate CAs, allowing for a more organized and manageable structure. Each subordinate CA might have its own policies governing how certificates are issued, allowing different configurations based on the security needs of various applications, such as SSL/TLS for websites versus code-signing for software validation.

By having designated subordinate CAs, organizations can implement specific security measures and certificate management processes. For example, certain subordinate CAs might be tasked with issuing certificates for internal use only, while others are authorized to issue certificates for external communication. This structure aids in risk management and simplifies compliance with diverse regulatory requirements.

In this context, while other choices may reference actions that CAs could potentially perform, they do not encapsulate the primary role that subordinate or intermediate CAs fulfill in issuing certificates according to defined policies