When a client connects to a server, the server presents a chain of certificates called the *server certificate chain*. A certificate chain usually has a root certificate authority (CA) certificate, one or more intermediate CA certificates, and the server's certificate. The client trusts the server by cryptographically verifying the entire server certificate chain. This process is called *server chain validation*. The client also challenges the server to prove it has the private key for the server certificate, called *proof of possession*. Together, server chain validation and proof of possession are called *server authentication*. To validate a server certificate chain, the client needs a copy of the root CA certificate used to issue the server's certificate. When connecting to websites, browsers come preconfigured with common CA certificates, so the client process is seamless.
0 commit comments