Understanding X.509 Public Key Infrastructure
X.509 PKI is a combination of standards, algorithms, data structures, software, hardware, organizations, and procedures needed to create, store, transfer, use, revoke, and otherwise manage X.509 certificates and certificate keys.
Sounds complicated, but we have just learned how X.509 PKI works on the World Wide Web. CAs issue certificates that are used by websites and verified by web browsers. That’s how millions of people using the web every day automatically verify the identity of websites. Some websites support the authentication of users using client certificates. In such cases, not only does the website present its certificate but also, the user’s web browser presents a client certificate to the site so that the site can verify the client certificate, authenticate, and authorize the user.
X.509 PKI is not only used for the web. X.509 certificates are used for mail transfer, communication of automated computer systems...