What is a client certificate used for?To authenticate the subordinate CATo authenticate the CATo authenticate the clientTo authenticate the server

A client certificate is primarily used to authenticate the client in a client-server architecture. When a client connects to a server, the server may require proof of the client's identity to establish a secure connection. Here’s a breakdown of the options you presented:

1. To authenticate the subordinate CA: This is not the primary purpose of a client certificate.
2. To authenticate the CA: A client certificate does not authenticate the Certification Authority (CA) itself.
3. To authenticate the client: This is the correct answer. A client certificate verifies the identity of the client to the server, ensuring that only authorized clients can establish a connection.
4. To authenticate the server: Server authentication usually involves server certificates, not client certificates.

Final Answer

To authenticate the client.