Public key infrastructure concepts

The public key infrastructure provides asymmetric techniques using two keys: a public key and a private key. There is a certificate hierarchy, which is called the certificate authority, that manages, signs, issues, validates, and revokes certificates. Let's first look at the components of the certificate hierarchy. A certificate is known as an X509 certificate.

Certificate hierarchy

The Certificate Authority (CA) is the ultimate authority as it holds the master key, also known as the root key, to sign all of the certificates that it gives the Intermediary, which then in turn issues to the requester:

Figure 1: Certificate hierarchy

• Online CA: An internal online CA is always up and running so that people in the company can request a certificate at any time of the day or night. The environment would not be a government or a top security environment.
• Offline CA: An offline CA is for a military or secure environment where clearance and vetting must be completed before...