What is PKI (Public Key Infrastructure)?

PKI (Public Key Infrastructure) is the entire trust system that makes SSL certificates work. Think of PKI as a network of official agencies that create, manage, and verify digital certificates to prove websites are legitimate. Just as you need a government system to issue driver’s licenses, PKI is the system that issues and manages SSL certificates to keep the internet secure.

How PKI Works

PKI creates a framework of trust that enables secure communications across the internet:

Certificate Authorities (CAs): Organizations that issue and validate certificates
Registration Authorities: Entities that verify identity before certificate issuance
Certificate Repositories: Databases that store and distribute certificates
Certificate Revocation Systems: Infrastructure to invalidate compromised certificates
Trust Stores: Collections of trusted root certificates in browsers and devices

Components and Trust Chain

The PKI system relies on a hierarchical trust model where root certificates anchor the entire system. Intermediate certificates bridge between roots and end-entity certificates, creating verifiable chains of trust. This structure allows browsers to validate that any certificate they encounter was issued by a trusted authority, ensuring secure communications across the global internet infrastructure.