A Certificate Authority is the trusted entity that issues, signs, and manages digital certificates. Without CAs, there would be no reliable way to verify identities online. Every secure connection starts with trust in a CA.
Imagine you need to buy a house. Before the bank hands over the mortgage, a notary verifies the seller's identity, checks that the property documents are legitimate, and stamps everything with an official seal. Without the notary, neither you nor the bank could trust that the transaction is valid.
A Certificate Authority (CA) plays the same role in the digital world. It is the trusted third party that verifies the identity of an entity (a website, an organization, a device) and issues a digital certificate confirming that identity. The certificate binds a public key to the verified identity, and the CA's digital signature on the certificate is the seal that makes it trustworthy.
Every time your browser establishes an HTTPS connection, it checks whether the server's certificate was issued by a CA it recognizes. If the CA is trusted, the connection proceeds. If not, you see a security warning. This simple mechanism (verify the issuer, trust the certificate) is the foundation of online trust.
The requester generates a public/private key pair. The private key stays secret and never leaves the requester's system. The public key will be included in the certificate.
The requester creates a CSR, a structured message containing the public key, the desired subject name (e.g., www.example.com), and other identifying details. The CSR is digitally signed with the requester's private key, proving they possess the corresponding key.
The CA verifies the requester's identity. For a public TLS certificate, this might involve proving control of the domain via a DNS record or HTTP challenge. For an organization-validated certificate, it means checking legal registration documents. For a private CA, verification might follow internal policies, such as checking an Active Directory record or an approval workflow.
Once the identity is verified, the CA constructs the certificate, embedding the public key, subject information, validity dates, and extensions, and signs it with the CA's own private key. This signature is what clients will verify to establish trust.
The signed certificate is returned to the requester, who installs it on the relevant server, device, or application. From this moment, any client that trusts the issuing CA will accept the certificate as valid.
Use a public CA. Visitors need to trust your certificate without any special configuration. Their browsers already include the public CA's root in their trust store.
Use a private CA. You control the trust store of all internal systems, so there is no need to involve a public CA. This also avoids per-certificate costs and gives you full control over policies.
Use a private CA. Client certificates for VPN access, Wi-Fi authentication, or smart card login should be issued by an internal CA whose root is deployed to corporate devices.
Use a private CA. Devices you manufacture or manage authenticate to your infrastructure using certificates you control. A private CA lets you define custom validity periods, key algorithms, and revocation policies suited to your devices.
Use a public CA for software distributed to external customers. Use a private CA for internal scripts and tools where you control the endpoints.
Use a private CA. Service-to-service communication within your infrastructure should use certificates from an internal CA. This is the foundation of zero-trust architectures where every service proves its identity to every other service.
Run your own private CA — Evertrust PKI lets you deploy a fully featured private Certificate Authority with root and intermediate CA hierarchies, customizable certificate profiles, and policy-based issuance, all through a modern, auditable platform.
Automate issuance at scale — Support for ACME, SCEP, EST, and REST APIs means certificates can be requested and deployed automatically by servers, devices, and CI/CD pipelines, with no manual intervention required.
Enforce governance — Define certificate policies, approval workflows, naming constraints, and key algorithm requirements. Every issuance is logged and auditable, meeting the governance expectations of enterprise PKI deployments.
Unified visibility — Whether your certificates come from public CAs, private CAs, or both, Evertrust provides a single dashboard to monitor, alert, and report on your entire certificate estate.
