What Is a Private CA? When to Run Your Own Certificate Authority

Executive summary — Not every certificate needs to be trusted by the public internet. For internal systems, devices and services, organisations often run their own private certificate authority (CA). This explainer defines a private CA, compares it with a public CA, sets out when running your own makes sense, explains the ways to run one and lists the responsibilities that come with it. For the wider PKI picture, see eMudhra's enterprise guide to PKI.

What a private CA is

A private certificate authority is a CA that an organisation operates for its own use. It issues digital certificates that are trusted only within that organisation's systems, rather than by the public internet.

Public CAs issue certificates that browsers and operating systems trust automatically. A private CA's root is trusted only by the systems the organisation configures to trust it, which gives the organisation full control over policy and issuance.

Private CA vs public CA

The choice comes down to who needs to trust the certificate:

	Public CA	Private CA
Who trusts it	Every browser and operating system	Only systems you configure to trust your root
Typical uses	Public websites, customer-facing APIs, signed email to outsiders	Internal apps, mutual TLS, VPNs, devices, workloads
Rules	CA/Browser Forum Baseline Requirements and root-programme policies	Your own certificate policy
Validity periods	Capped, and falling to 100 days in 2027 and 47 days by 2029	Set by you, from minutes to years
Naming	Publicly resolvable domain names only	Internal hostnames, device IDs, custom fields
Volume and cost	Per-certificate cost and validation steps	Issue at whatever volume your infrastructure supports

The public validity schedule is explained in the 100-day certificate validity countdown. Those caps do not apply to privately trusted certificates, although short lifetimes are still good practice.

When to run your own CA

A private CA makes sense when you issue many certificates that do not need public trust. Common signs that you need one:

• Internal TLS for intranet applications, admin consoles and internal APIs.
• Mutual TLS between services, including workload identity platforms such as SPIFFE/SPIRE in production.
• VPN, Wi-Fi and network access using certificate-based authentication.
• Device identity at scale for laptops, mobile devices, IoT and operational technology.
• Custom policy needs, such as specific validity periods, naming conventions or extensions that public CAs cannot accommodate.

If a certificate will be presented to browsers or systems you do not control, it needs a public CA instead.

Three ways to run a private CA

• On-premise, self-operated: maximum control and data residency, but you own the hardware, HSMs, staffing and audits. See on-premise PKI.
• Managed private CA: a provider runs the CA infrastructure to your policy, so you keep control of trust without operating it. See managed PKI.
• Hybrid: an offline root kept under your control, with issuing CAs run on-premise or as a managed service.

The trade-offs are compared in detail in managed PKI vs on-premise PKI.

Considering a private CA for internal trust? eMudhra designs private PKI hierarchies with strong governance. Ask eMudhra how to run one.

Responsibilities of running a private CA

Operating a CA carries real responsibility. The basics are:

1. Design the hierarchy: an offline root, with one or more issuing CAs beneath it, so a compromised issuing CA can be replaced without rebuilding all trust.
2. Protect the keys: keep root and issuing keys in hardware security modules, with ceremonies and dual control for root operations.
3. Write the policy: document certificate types, validity, naming and approval rules in a certificate policy and practice statement.
4. Publish revocation: run CRLs and OCSP reliably, because a certificate you cannot revoke is a certificate you cannot fully trust.
5. Distribute the root: get your root into the trust stores of every system that needs it, and plan how you will rotate it.
6. Manage the lifecycle: discover, renew and revoke every certificate the CA issues.

Without lifecycle management, a private CA can create the same sprawl and expiry risks it was meant to solve.

How eMudhra CertiNext supports private CA operations

eMudhra CertiNext provides certificate lifecycle management that automates issuance, renewal, revocation and discovery for certificates, including those from a private CA. This keeps internal certificates visible and under control alongside public ones.

Backed by eMudhra's PKI expertise as a globally recognised trust provider, organisations can run private certificate authority services with strong governance, protecting root keys and enforcing consistent policy across the enterprise.

Frequently Asked Questions

What is a private certificate authority?

A private CA is a certificate authority an organisation runs for its own systems. Its certificates are trusted only by devices and applications configured to trust its root, not by the public internet.

When should I use a private CA instead of a public CA?

Use a private CA for internal services, mutual TLS, VPNs and device identity, where only your own systems need to trust the certificate. Use a public CA for anything presented to browsers or external parties.

Do CA/Browser Forum validity limits apply to private CAs?

No. The Baseline Requirements and shrinking lifetimes apply to publicly trusted TLS certificates. A private CA sets its own validity periods, though short-lived, automatically renewed certificates are still recommended.

Is it better to run a private CA in-house or use a managed service?

In-house gives maximum control but requires HSMs, skilled staff and audits. A managed private CA keeps policy under your control while a provider operates the infrastructure. Many organisations choose a hybrid with an offline root they control.

Run internal trust with confidence

eMudhra CertiNext automates the lifecycle of certificates from private and public CAs, keeping internal trust visible and governed. Explore CertiNext or talk to an eMudhra expert.