🏷️ Tech Topics:#Security#WebCrypto#PEM#JWK#X509#SSL_Certificate#OAuth2#ClientSide
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Security Cert & Key Converter (PEM ↔ JWK) and X.509 Inspector Guide

Managing cryptographic keys, RSA/ECDSA key pairs, and SSL/TLS X.509 certificates is an indispensable part of security architecture, OAuth2 / OpenID Connect (OIDC) integrations, and HTTPS server setup. Keys are represented in various standards: Privacy-Enhanced Mail (PEM) Base64 ASCII format vs. JSON Web Key (JWK, RFC 7517) used in JWT verification endpoints (.well-known/jwks.json). Converting between PKCS#8, SPKI, and JWK normally requires complex OpenSSL CLI commands. Furthermore, developers must inspect X.509 TLS/SSL certificates to verify Subject Alternative Names (SAN), Validity Periods, and SHA-256 fingerprints without risking private key leakage to remote servers. This tool executes 100% locally in your browser memory via native Web Crypto API, guaranteeing complete zero-trust privacy.

🔒Technical Specifications & Local Processing Architecture

All key import/export operations use the browser-native window.crypto.subtle engine (Web Crypto API). No private keys, certificates, or text strings ever leave your device memory.

✨ Core Capabilities

  • •Instant PEM to JWK conversion for RSA and ECDSA SPKI public keys & PKCS#8 private keys.
  • •Reverse JWK to PEM formatting for PKCS#8 private keys and SPKI public keys.
  • •X.509 SSL/TLS Certificate metadata inspection (Subject CN, Issuer, Validity D-Day, SAN domains).
  • •100% Client-Side Web Crypto API execution with zero network data transfer.

🚀 Step-by-Step Guide

  1. 1Paste your RSA/ECDSA key in PEM format or JWK JSON into the converter tab.
  2. 2The converted output is generated instantly in real-time.
  3. 3For X.509 certificates, switch to the Inspector tab and drop your .crt or .pem file.
  4. 4Review the validity status, remaining D-Days, SHA-256 fingerprint, and SAN domains.

💡Technical Deep-Dive & Detailed FAQ Guide

5 questions & detailed answers

Q1.What is the difference between PEM and JWK key formats?

PEM (Privacy-Enhanced Mail) uses Base64 ASCII blocks wrapped in header and footer lines (e.g. -----BEGIN PUBLIC KEY-----). JWK (JSON Web Key, RFC 7517) represents cryptographic keys as JSON objects containing parameters like "kty", "n", "e", or "crv", commonly used in OAuth2 and JWT verification.

Q2.Is it safe to paste private keys into this converter?

Yes, absolutely. Unlike remote converter tools, this tool performs all cryptographic operations 100% client-side inside your browser via Web Crypto API. No data is sent over the network.

Q3.What are Subject Alternative Names (SAN) in SSL certificates?

SANs allow a single X.509 SSL/TLS certificate to secure multiple domain names (e.g. example.com, api.example.com, *.example.com). Our inspector extracts and displays all SAN domains registered in the certificate.

Q4.What algorithms are supported for PEM to JWK conversion?

This tool supports RSA keys (RS256, RS384, RS512) and Elliptic Curve (ECDSA) keys (P-256, P-384, P-521) for both public SPKI and private PKCS#8 Key formats.

Q5.Can I check certificate expiry dates before deploying to production?

Yes. The X.509 inspector parses your certificate validity dates, calculates the exact remaining D-Days until expiry, and highlights warnings if the certificate is near expiration.