What is a Root Certificate Authority (CA)?
Keytos Team |
- Updated: August 6, 2026What is a Root Certificate Authority?
A root certificate authority (CA), often referred to as the foundation of trust in your PKI system, is pivotal when designing and implementing a public key infrastructure (PKI). The root CA is the top-most certificate in a certificate chain, and it serves as the trust anchor for all certificates issued within that chain. In essence, the root CA is the entity that vouches for the authenticity of all subordinate CAs and end-entity certificates underneath it. This is helpful for a couple of reasons:
- Simplified Trust Model: Instead of having to trust every individual certificate, you only need to trust the root CA. If the root CA is trusted, then all certificates issued by subordinate CAs under that root are also trusted.
- Centralized Management: The root CA allows for centralized management of trust within an organization. By controlling the root CA, administrators can enforce security policies and manage the lifecycle of all subordinate certificates effectively.
- Central Revocation: If a subordinate CA or end-entity certificate is compromised, the root CA can revoke its trust, ensuring that the integrity of the entire PKI system remains intact.
Why is a Root CA So Important To Protect?
Given its role as the foundational trust element for your entire certificate chain, the root CA’s security is paramount. If malicious entities gain access to your root CA, they essentially have a master key to your applications and devices. Hence, securing the root certificate authority is vital. Root CAs should always be protected by Hardware Security Modules (HSMs) and can also be kept offline to minimize exposure to potential threats.
Do I Need a Root CA In My PKI Environment?
This is a great question! The short (and only) answer is yes, you need a root CA in your internal private PKI. If you’re deploying a single-tier PKI hierarchy, your root CA will also serve as your issuing CA. If you’re deploying a two-tier PKI hierarchy (recommended), your root CA will be the trust anchor for your issuing CA. In either case, the root CA is the foundation of trust for your entire certificate chain.
Large enterprises can use one root CA and chain up multiple subordinate/issuing CAs. This allows them to have an Intune CA, Smart Card CA, and an SSL CA with only the one Root CA certificate to trust on their devices.
The same is also true for small and medium-sized businesses (SMBs). While they might only have one issuing CA for Wi-Fi authentication, they are still recommended to have a root CA as a root of trust that is used to sign the issuing CA. This allows them to have a root of trust that can be used to sign additional issuing CAs in the future if they need to expand their PKI environment.
How Many Levels Should My PKI Hierarchy Have?
CA hierarchy is, put simply, the number of tiers (levels) of CAs that are chained together. Choosing the number of tiers in a CA hierarchy is vital to effective PKI planning. There are three options to choose from:
- Single/One-Tier Hierarchy
- Two-Tier Hierarchy (recommended)
- Three-Tier Hierarchy.
Root CAs play an important role in all of these tiers, with each tier having different roles for the root CA and, hence, different ways for the root CA to interact with the issuing CA. Check out this blog outlining the difference between a root CA and an issuing CA to learn more. We recommend organizations use a Two-Tier PKI Hierarchy, but feel free to check out our blog defining what is a CA hierarchy and which CA hierarchy you should use for more information on that front.
What Does It Take To Deploy and Run a Root CA?
Maintaining your own root CA requires money, manpower, and expertise. It is vital to take into consideration the resources that your organization may or may not have to manage the many responsibilities associated with a root CA, like CRL updates, HSM management, and a secure storage location for the CA.
Traditionally, organizations may use Active Directory Certificate Services (ADCS) to deploy and manage their root CA. In today’s cloud-first world, organizations can also use a cloud-based PKI solution like EZCA to deploy and manage their root CA. EZCA allows you to create a root CA in Azure without the overhead of managing the infrastructure yourself. With EZCA, you can easily set up a root CA that is secure and compliant with industry standards, ensuring that all certificates issued by the root CA are trusted within your organization. Plus, you can chain up to an existing on-premises root CA if you already have one in place.
EZCA offers a 1-month free trial, allowing you to explore its features and capabilities before committing to a subscription. Plus, the Keytos team is available to assist you with any questions or concerns you may have during your trial period. Whether you’re looking to issue SSL certificates for internal websites, Smart Card certificates for user authentication, or device certificates for VPN and Wi-Fi access, EZCA can help you get started with your private PKI quickly and easily.
