📖 Description
1. Why is Matching Verification Necessary?
A CSR (Certificate Signing Request) is generated based on a private key, and the two are mathematically and logically bound in a unique pair. If they do not match, severe consequences can occur:
- Issued Certificate Becomes Invalid: If you submit a CSR that does not match the private key in your possession, the certificate issued by the CA cannot be installed on your server.
- Deployment Errors: Servers (such as Nginx or Apache) will throw an
X509_check_private_key:key values mismatch error when loading the certificate and private key, causing service downtime.
- Management Chaos: When managing multiple domains or frequently renewing certificates, it's easy to mix up
.csr and .key files generated at different times.
2. Core Functionality Analysis
This site's tool provides an intuitive verification experience through underlying cryptographic logic:
A. Modulus Fingerprint Comparison
- Technical Principle: The tool extracts the public key modulus from the CSR and the modulus from the private key, then performs SHA-256 hash calculation on each.
- Judgment Logic: If the modulus hash values of both files are identical, it confirms that the CSR was generated from that private key, meaning they belong to the same key pair.
B. Strong Format Compatibility
- CSR Files: Supports
.csr, .req formats, must contain the -----BEGIN CERTIFICATE REQUEST----- tag.
- Private Key Files: Supports common
.key, .pem formats, including RSA and PKCS#8 formats (containing the -----BEGIN PRIVATE KEY----- tag).
C. Absolute Privacy Protection: Pure Local Computation
- Core Security: All verification logic is executed locally in your browser.
- No-Upload Principle: While a CSR is public, the private key is the foundation of server security. This tool will never upload your private key to any server. The entire comparison process is completed in local memory, and data disappears immediately upon page refresh.
3. Verification Result Status Reference
| Status Feedback |
Visual Indicator |
Meaning & Suggestion |
| Perfect Match |
Green Success |
The CSR and private key are paired. You can safely submit the CSR to a CA for certificate issuance. |
| Mismatch |
Red Alert |
The two are not a pair. Please locate the correct private key or regenerate a new CSR and Key pair. |
| Cannot Parse (Invalid) |
Yellow Hint |
The input content is not in a valid CSR or private key format. Please check if the copy is complete. |
4. Brief Operation Process
- Prepare Data: Open your CSR and private key files using an editor (e.g., Notepad, VS Code).
- Paste Content:
- In the "CSR Content" box, paste the entire text including
-----BEGIN CERTIFICATE REQUEST-----.
- In the "Private Key Content" box, paste the entire text including
-----BEGIN PRIVATE KEY-----.
- Start Verification: Click the "Check Match Now" button.
- View Conclusion: The system will display two SHA-256 string fingerprints.
- If the fingerprints are the same, the conclusion shows "Match Successful".
- If the fingerprints differ, the system will prompt "Match Failed".
5. Why Choose This Site's Matching Check Assistant?
- Simpler than Command Line: No need to enter complex OpenSSL commands (e.g.,
openssl req -modulus ...). Visual results are clear at a glance.
- Instant Feedback: Utilizes efficient front-end JS algorithms to produce comparison results instantly.
- Completely Free: No login required, unlimited usage. An essential tool for improving HTTPS deployment success rates.
- Privacy Assured: Built specifically for developers with high-security requirements, ensuring the tool never oversteps its bounds.