Certificate Authority (CA)

A Certificate Authority (CA) is a trusted public organization that issues electronic certificates (digital certificates) to verify identities or other information on the internet. CAs are broadly divided into two types: "Root Certificate Authorities" and "Intermediate Certificate Authorities."

A Root Certificate Authority is the highest-level certificate authority that can validate its own authenticity and issue certificates to other certificate authorities. In contrast, an Intermediate Certificate Authority cannot validate itself and must be certified by a higher-level certificate authority. The certificates used by a root CA to validate itself are called root certificates, while those issued by a higher-level CA to validate an intermediate CA are called intermediate certificates.

CAs consist of three main components:

1. Registration Authority (RA): Examines the ownership information submitted by applicants for electronic certificates.
2. Issuing Authority (IA): Issues or revokes electronic certificates based on requests from the RA.
3. Repository: Manages and provides information about the CA and the validity of electronic certificates. Root and intermediate certificates can be downloaded from the repository.

Publicly recognized electronic certificates must be issued by a publicly recognized CA, known as a Public Certificate Authority. On the other hand, organizations or individuals can establish a Private Certificate Authority, which operates under their own internal standards. Certificates issued by private CAs lack official public recognition but are often used for specific internal purposes, such as user authentication within an organization (e.g., client certificate-based authentication). In such cases, private CAs can be used for issuing and managing these electronic certificates.