Public key infrastructure and certificate authorities

Public key infrastructure (PKI) defines the architecture for secured communications between users. PKI defines a certificate authority (CA) that contains several attributes to be used between users that establish communications.

PKI provides several services:

• Authentication: To prove to each side that the other side is who it claims to be
• Integrity: To prove that data has not been changed during transmission
• Confidentiality: To prove that no one can read the data during transmission

PKI standardized the process of using certificates and using private and public keys for secure communications between entities.

PKI is mostly used to connect to web servers using Secure Socket Layer/Transport Layer Security (SSL/TLS). In this section, we will describe the process and, in the SSL/TLS and Proxies section, later in this chapter, we will get to the bits and bytes.

First, let's see how a client connects...