CAS

A certificate authority (CA) is a trusted entity that issues digital certificates used to establish secure communications over networks. These organizations play a crucial role in public key infrastructure (PKI) by verifying the identity of individuals, organizations, or devices before issuing cryptographic certificates.

CAs operate by binding public keys to verified identities through digital certificates. When a user or organization requests a certificate, the CA performs identity verification processes that may include document validation, domain ownership confirmation, or more extensive background checks depending on the certificate type. Once verified, the CA digitally signs the certificate using its private key, creating a trust chain that browsers and other systems can validate.

The hierarchical structure of CA systems typically includes root CAs at the top, which are self-signed and pre-installed in operating systems and browsers. These root CAs may delegate authority to intermediate CAs, which handle the actual certificate issuance process. This structure allows for scalable certificate management while maintaining security standards.

Web browsers and operating systems maintain lists of trusted root CAs. Certificates issued by these trusted authorities are automatically accepted by most software, while certificates from unknown CAs trigger security warnings. This trust model enables secure HTTPS connections, email encryption, code signing, and other cryptographic applications.

Prominent commercial CAs include companies like DigiCert, Sectigo, and GlobalSign. However, organizations can also operate their own private CAs for internal purposes. The CA/Browser Forum establishes industry standards and policies that govern certificate issuance practices.

Security breaches involving CAs can have widespread consequences, as compromised CAs could issue fraudulent certificates. To mitigate this risk, CAs must implement strict security measures, undergo regular audits, and maintain certificate revocation systems to invalidate compromised or expired certificates.