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BackWhat is a Certificate Revocation List (CRL)?
A Certificate Authority (CA) digitally signs and publishes a Certificate Revocation List (CRL) to identify certificates it revoked before their expiration date. Systems and applications use CRLs during certificate validation to determine whether they should still trust a certificate.
CRLs are a fundamental component of Public Key Infrastructure (PKI). They help prevent compromised, misused, or incorrectly issued certificates from being accepted for authentication or encrypted communications.
Why is a Certificate Revocation List important?
Digital certificates are trusted only while they remain valid and uncompromised. If a certificate’s private key is exposed, issued to the wrong entity, or no longer meets trust requirements, simply waiting for it to expire creates unnecessary security risk.
A CRL provides a centralized way for Certificate Authorities to publish revoked certificates, enabling systems to reject certificates that should no longer be trusted. This helps preserve the integrity of secure communications and identity verification across enterprise environments.
How does a Certificate Revocation List work?
The CRL process follows a straightforward lifecycle:
| Step | Description |
| Certificate revocation | The Certificate Authority determines that a certificate is no longer trusted. |
| CRL update | The revoked certificate’s serial number is added to the latest CRL. |
| CRL publication | The updated CRL is digitally signed and published by the CA. |
| Certificate validation | Systems retrieve or reference the CRL while validating certificates. |
| Trust decision | If the certificate appears on the CRL, it is rejected according to security policies. |
Because CRLs are updated periodically rather than continuously, there can be a delay between certificate revocation and the availability of an updated revocation list.
Certificate Revocation List (CRL) vs. OCSP
Both CRLs and the Online Certificate Status Protocol (OCSP) help determine whether a certificate has been revoked, but they use different approaches.
| Feature | Certificate Revocation List (CRL) | Online Certificate Status Protocol (OCSP) |
| Validation method | Downloads a list of revoked certificates | Checks the status of an individual certificate |
| Data retrieved | Complete revocation list | Status of a single certificate |
| Network usage | Larger revocation list retrieval | Smaller certificate-specific status checks |
| Best suited for | Periodic validation or environments using cached revocation data | Online certificate status validation |
Many PKI deployments support both mechanisms depending on operational and security requirements.
How Hexnode supports certificate management
Managing certificates requires administrators to handle deployment, updates, removal, and replacement when certificates expire or become untrusted. Hexnode UEM enables administrators to centrally deploy and manage digital certificates across supported endpoints while enforcing security policies and compliance requirements. By simplifying certificate deployment and management across supported devices, Hexnode helps organizations support certificate-based authentication strategies.
Challenges of using CRLs
While CRLs remain widely used, they can introduce operational considerations, particularly in large environments. Common challenges include larger revocation lists, periodic update intervals, network requirements for obtaining the latest CRL, and ensuring that all systems consistently enforce revocation checks.
Organizations should establish processes to monitor certificate status, update revocation information regularly, and replace revoked certificates promptly to maintain PKI trust.
FAQs
Not necessarily. Since CRLs are updated periodically, systems may use a previously retrieved CRL until a newer version becomes available according to the CA’s update schedule.
