Certificate validation is the process of confirming that a digital certificate is trustworthy, has been issued by a legitimate certificate authority (CA), and has not been altered or revoked. It plays a critical role in ensuring that HTTPS connections remain private, authentic, and tamper-proof.
HTTPS leverages public-key encryption to safeguard browser communications from being intercepted or altered during transit across the Internet. Visiting browsers are supplied with a public key by servers, which is then utilized to set up an encrypted connection for all following data transfers. However, receiving a working public key does not guarantee that the server truly belongs to a trusted company or entity. Man-in-the-middle attackers have the capacity to tamper with networks to distribute their own keys, thereby jeopardizing any communication.
To prevent this, browsers validate the certificates used by HTTPS servers. These digital certificates act as machine identities that bind a public key to an organization, individual, or device. This linkage is affirmed by a trusted certification authority, which uses a combination of automated and manual checks to verify the certificate holder’s identity against approved databases.
Why certificate validation matters
Without certificate validation, anyone could pose as a trusted site. Even with strong encryption, attackers could insert themselves between a user and a website, intercepting or altering data. Validation ensures that users are securely connected to the real, intended site—not an impostor.
How certificate validation works
Certificate authorities and the “chain of trust” both ensure that digital certificates are trustworthy and secure.
Role of certificate authority (CA)
Certificate authorities use a private key to cryptographically sign all certificates they issue. This signature serves as proof that the certificate came from a trusted CA and has not been altered. The CA asserts ownership of this signing key by possessing a root certificate, also known as a trust anchor, that corresponds to the public key. The creation, management, and usage of a root certificate by CAs are strictly regulated and audited, in compliance with the baseline requirements set by the CA/B Forum. CAs also follow defined protocols for issuing certificates—including certificate enrollment methods such as the automated certificate management environment (ACME), simple certificate enrollment protocol (SCEP), and enrollment over secure transport (EST)—to streamline the request and approval process.
Certificate chain of trust
A “chain of trust” is a hierarchical structure in which each certificate inherits trust from the one above it, ultimately linking back to a trusted root certificate. Because of the high value of root certificates and the potential risks associated with their compromise, they are seldom used to issue end-entity certificates directly. Instead, intermediate certificates form a chain of trust between an end-entity certificate and a root certificate.
These intermediate certificates issue certificates for their clients, ensuring that each certificate in the chain is cryptographically linked back to a trusted root certificate. Many software applications—such as browsers—rely on the trustworthiness of this root certificate to validate SSL/TLS connections.
Steps in the certificate validation process
Once a potential certification path has been established, browsers authenticate it by utilizing the data embedded within the certificates. A path is deemed valid if browsers can cryptographically confirm that, starting from a trust anchor, each certificate in the chain was signed using the private key corresponding to the one above it—down to the end-entity certificate. RFC 6960 provides a conventional algorithm that browsers adhere to when validating a certification path of X.509 certificates.
Browsers verify all certificates in the chain, starting from the trust anchor, checking both the core data and required extensions. If the process completes without discrepancies, the path is valid. If inconsistencies are found, the path is marked invalid. Regardless of extensions, browsers always validate basic certificate data, such as the signature and issuer.
The sequence of validations is as follows:
1. The browser confirms the certificate’s integrity
The certificate’s signature is verified using public-key cryptography. If tampered with, the browser will reject it.
2. The browser checks the certificate’s validity period
A certificate’s validity period defines the window during which the signing CA guarantees to maintain its status information. Browsers reject certificates that are not yet valid or have already expired at the time of the check.
3. The browser checks the certificate’s revocation status
Certificates are expected to remain valid for their entire duration, but private key compromise can require revocation. In such cases, the CA must revoke the certificate using the following revocation mechanisms:
- Certificate revocation lists (CRLs): CAs periodically issue signed, time-stamped lists of revoked certificates. These are published in public repositories and consulted during validation. A drawback is that the CRL’s update frequency limits revocation awareness.
- Online certificate status protocol (OCSP): Defined in RFC 6960, OCSP allows browsers to query a CA’s server in real time for the revocation status of a specific certificate.
- OCSP Stapling: This improves performance and speed by allowing servers to “staple” a signed OCSP response to the TLS handshake.
4. The browser verifies the issuer
X.509 certificates include an issuer (the entity that signs the certificate) and a subject (the entity being certified). Browsers ensure that the issuer of each certificate matches the subject of the preceding certificate in the path.
5. Constraints processing
Browsers then check certificate constraints, if defined by the CA. Each certificate in the path may include constraints—such as permitted names, usage, or policies—that must be followed by all subsequent certificates.
Shorter certificate lifecycles demand 47-day renewal readiness
Industry programs led by Google and Apple are driving certificate lifetimes down to 90 days, with operational best practice now calling for fully automated renewal roughly halfway through—about every 47 days. Organizations that still rely on manual workflows experience significantly more renewal events and a higher risk of unexpected expiry outages.
The three main types of certificate validation each offer a different level of security, verification, and browser visibility:
Types of certificate validation
| Type | Assurance Level | CA Checks | Use Case | Browser Display |
|---|---|---|---|---|
| Domain validation (DV) | Low | Domain control only | Blogs, internal sites | Padlock |
| Organization validation (OV) | Medium | Domain + organization validation | Small businesses | Padlock + org name in certificate |
| Extended validation (EV) | High | Extensive org validation | Financial institutions | Padlock + org name in URL bar |
To maintain secure, trusted connections, organizations must ensure that digital certificates are properly validated and managed. The table below outlines the most common certificate validation failures, their root causes, and the steps needed to resolve them:
Common certificate validation failures
| Issue | Cause | Fix |
|---|---|---|
| Expired certificate | Passed its validity period | Renew it; automate future renewals. |
| Revoked certificate | Key compromise, domain loss | Replace the certificate and investigate. |
| Invalid chain | Missing intermediates | Install correct chain and verify via OpenSSL. |
| Untrusted CA | CA not in browser trust store | Use a trusted CA or distribute your root. |
FAQs
What is the difference between certificate validation and certificate verification?
Verification usually refers to a single cryptographic check of a certificate’s signature. Validation is broader: it verifies the signature and confirms revocation status, chain of trust, constraints and validity period.
How does certificate validation prevent man-in-the-middle attacks?
Certificate validation helps ensure that the digital certificate presented by a server is authentic, issued by a trusted CA, and hasn’t been altered or revoked. By verifying the certificate’s signature, chain of trust, and revocation status, browsers can confirm they are communicating with the intended website—not a malicious third party posing as that site. This process helps protect against man-in-the-middle (MITM) attackers from using forged or self-signed certificates to intercept or modify encrypted data.
How can I check if a certificate is valid?
In a terminal run openssl s_client -connect host:443 -servername host. Review the “Verify return code: 0 (ok)” line, expiration dates and reported chain. Browser developer tools show the same details under the Security tab.
What is OCSP in certificate validation?
The online certificate status protocol (OCSP) lets a client query a CA’s responder in real time to confirm whether a certificate is good, revoked, or unknown, avoiding the delays of downloading full CRLs. OCSP stapling allows the server to attach a signed OCSP response, speeding up the handshake.
CyberArk and certification validation
CyberArk Certificate Manager automates discovery, renewal and revocation across thousands of machine identities, continuously monitors chain-of-trust integrity, and staples OCSP responses to improve performance and user experience. Its policy-based automation handles the looming 47-day renewal cadence without manual effort, helping teams reduces the risk of unexpected expiry outages. It enforces policy-driven key management and provides dashboards and alerts so teams can remediate failures before they disrupt production. All of this aligns with robust machine identity security strategies to maintain compliance and scale automation.
