SSL/TLS Certificate & ASN.1 X.509 Parser
Parse PEM and ASN.1 DER encoded X.509 SSL/TLS certificates, verify Subject Alternative Names (SAN), calculate SHA-256 fingerprints, and inspect validity expiration countdowns directly in browser memory.
The SSL/TLS Certificate & ASN.1 X.509 Parser is a fast, accurate Security Tools utility designed to parse pem and asn.1 der encoded x.509 ssl/tls certificates, verify subject alternative names (san), calculate sha-256 fingerprints, and inspect validity expiration countdowns directly in browser memory. entirely in your browser with zero server data storage.
SSL/TLS Certificate & ASN.1 X.509 Parser
Parse PEM and ASN.1 DER encoded X.509 SSL/TLS certificates, verify Subject Alternative Names (SAN), calculate SHA-256 fingerprints, and inspect validity expiration countdowns.
ITU-T X.509 & ASN.1 DER Certificate Architecture
Public Key Infrastructure (PKI) relies on X.509 certificates to authenticate remote web servers and secure encrypted HTTPS connections. Understanding how certificates are constructed helps diagnose trust chain errors, invalid SAN mismatches, and unexpected expirations.
Key X.509 Certificate Extensions & Fields
- TBSCertificate (To-Be-Signed): The core ASN.1 sequence containing serial number, validity dates, subject DN, issuer DN, and Subject Public Key Info (SPKI).
- Subject Alternative Name (SAN - OID 2.5.29.17): Specifies all hostnames, IP addresses, and wildcard domains authorized to present this certificate.
- Key Usage (OID 2.5.29.15): Restricts the cryptographic purposes of the public key (e.g. Digital Signature, Key Encipherment).
- Fingerprints / Thumbprints: Cryptographic digests (SHA-256 / SHA-1) calculated over the entire DER-encoded certificate bytes for fast pinning and comparison.
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Systems & Security Engineers • Applied Cryptography & High-Performance Web Tools
How to Use SSL/TLS Certificate & ASN.1 X.509 Parser
Input PEM Certificate
Paste your PEM certificate text (with -----BEGIN CERTIFICATE----- headers) or upload a .crt, .pem, or .cer file.
Inspect Validity Countdown
Check whether the certificate is currently active, expired, or approaching its renewal deadline.
Review Subject & Issuer
Verify the Common Name (CN), Organization (O), and Certificate Authority (CA) issuer details.
Extract SANs & Fingerprints
Inspect all Subject Alternative Name DNS patterns and copy the SHA-256 and SHA-1 certificate thumbprints.
Practical Examples & Conversions
Cloudflare TLS PEM string
Valid certificate with SANs: *.toolbox.vishnudigital.com
Frequently Asked Questions (PAA)
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Authoritative Standards & Citations
Calculations and algorithms on this page are implemented and verified in strict accordance with the following official technical specifications:
RFC 7519: JSON Web Token (JWT)
Standardized compact, URL-safe means of representing claims to be transferred between two parties.
Web Cryptography API Specification
Standard JavaScript API for performing basic cryptographic operations in web applications.
RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace
Definition of uniform format and generation algorithms for UUIDs.