Calculator Form
How to Use This Calculator
- Add a record label, owner, and environment if needed.
- Paste a PEM private key or upload a key file.
- Enter the passphrase if the key is encrypted.
- Choose the output preference for your review workflow.
- Press the button to derive the public key.
- Review fingerprints, algorithm details, and the PEM output.
- Download the CSV record or export the result as PDF.
Formula Used
RSA: public key = (n, e). The modulus n and exponent e are extracted from the private key structure.
Elliptic Curve: public key point Q = d × G, where d is the private scalar and G is the base point.
DSA: public component y = gx mod p, using the private value x and domain parameters.
The tool also hashes the derived public PEM with SHA-256 and SHA-1 to create comparison fingerprints.
Example Data Table
| Record Label | Algorithm | Bits | Curve | SHA-256 Fingerprint |
|---|---|---|---|---|
| VPN Gateway Key | RSA | 2048 | Not applicable | 7A:14:92:8F:21:XX:XX:XX:AE:1B:34:XX:XX:XX:54:91 |
| API Signing Key | EC | 256 | prime256v1 | 1B:AC:09:32:77:XX:XX:XX:04:C6:11:XX:XX:XX:3E:AF |
| Archive Validation Key | RSA | 4096 | Not applicable | FE:83:30:AB:66:XX:XX:XX:45:19:88:XX:XX:XX:10:CD |
Public Key Derivation Guide
Why This Key Tool Matters
Public key derivation is a common security task. It helps during certificate work, access reviews, and deployment checks. Teams often store only private material in a secure vault. They later need the matching public output for distribution. This calculator speeds up that review. It also reduces manual command mistakes.
What The Calculator Returns
The tool reads a supported private key and extracts its public section. It shows the algorithm, size, fingerprint values, and curve details when available. It also prints the PEM public key block. That output is useful for validation, documentation, and secure sharing. You can also download a CSV record or export a PDF summary.
How Public Key Derivation Works
The process depends on the algorithm. RSA public data uses the modulus and public exponent. Elliptic curve systems derive the public point from the private scalar on the selected curve. DSA uses domain parameters and a matching public component. In each case, the public key is mathematically linked to the private key. The reverse path remains computationally infeasible.
Operational Benefits
This page is useful for audits, migrations, and key inventory tasks. It helps compare records across servers, vault exports, and application settings. It also supports passphrase protected keys. The result section appears above the form, so repeated checks stay easy. The clean layout keeps the workflow focused and readable.
Many administrators also use it when rebuilding environments. A quick comparison between stored fingerprints and regenerated output can reveal mismatched files, wrong passphrases, or copied configuration errors early during reviews.
Security Use Notes
Only process keys you are authorized to handle. Avoid testing live production secrets on shared systems. Prefer secure internal hosting for real operations. Use exported reports carefully because they may reveal metadata. Public keys are shareable, but private keys are not. Review retention policies before saving any report file.
Best Practice Summary
Use this calculator when you need a fast, structured view of derived public key data. Verify fingerprints before distribution. Confirm curve names and bit lengths during reviews. Keep passphrases protected at all times. Archive only the minimum output required. Small checks like these improve operational security and documentation quality.
FAQs
1. What key formats does this page support?
It supports PEM private keys that OpenSSL can read. That usually includes RSA, EC, and some DSA private keys. Encrypted keys also work when the correct passphrase is supplied.
2. Does this tool show my private key after processing?
No. The page does not print the private key in the result area. It only shows derived public details and the public PEM block.
3. What happens if the passphrase is wrong?
The key will not load. The page will return an OpenSSL error or a simple failure message. Recheck the passphrase and key format before trying again.
4. Why are fingerprints included?
Fingerprints help you compare keys quickly. They are useful during audits, migrations, and deployment checks when you need to verify that records match the expected public output.
5. Can I export the result for documentation?
Yes. You can download a CSV report for recordkeeping. You can also export the visible result section as a PDF for review packs or audit notes.
6. Does this page convert keys into SSH format?
No. This version derives a standard public PEM output. SSH formatting can be added later, but it is not included in this build.
7. Why is curve information sometimes blank?
Curve names apply to elliptic curve keys only. RSA keys do not use named curves, so the result correctly shows that curve data is not applicable.
8. Is this suitable for production secrets?
Use caution. Handle only keys you are authorized to process. For real environments, host this page internally and follow your organization’s secret handling rules.