13.3. User-Authentication Methods
There are a number of authentication systems in use today, but I'm going to focus on the ones you're likely to be confronted with on the Network+ exam.
13.3.1. Public Key Infrastructure (PKI)
Public Key Infrastructure (PKI) is a system that links users to public key that verifies the user's identity by using a certificate authority (CA). Think of a CA as an online notary public—an organization that's responsible for validating user IDs and issuing unique identifiers to confirmed individuals to certify that their identity can really be trusted. Figure 13.9 shows how the CA process works in relation to two users.
Figure 13.9. The certificate authority process
PKI allows people to communicate with each other ...