Certificate & ASN.1 Tools
X.509 certificate parsing, ASN.1 structure viewer, OID conversion tools.
X.509 Certificate Parser
Usage
X.509 Certificate Introduction
X.509 is the standard format for public-key certificates, widely used in TLS/SSL protocols. ASN.1 (Abstract Syntax Notation): a language for describing data structures. DER (Distinguished Encoding Rules): a binary encoding of ASN.1. OID (Object Identifier): dot-separated numbers (e.g. 1.2.840...) that uniquely identify algorithms, attribute types, etc.
Steps
Certificate Parsing: 1. Switch to "X.509 Parser" tab; 2. Paste PEM certificate (starting with -----BEGIN CERTIFICATE-----); 3. Click "Parse" to view subject, issuer, validity, serial number, public key, fingerprint, etc. OID Conversion: 1. Switch to "OID Converter" tab; 2. Enter OID string (e.g. 1.2.840.113549) to convert to Hex; 3. Enter Hex string to convert to OID. ASN.1 Parsing: 1. Switch to "ASN.1 Parser" tab; 2. Enter Hex string; 3. Tool parses the structure according to ASN.1 rules.
Notes
Certificate parsing only supports PEM format; DER format must be converted to PEM first. OID conversion is based on node-forge. ASN.1 parsing is a simplified implementation and may not handle complex structures completely. You can export PEM from browser to parse HTTPS website certificates. This tool runs entirely in the browser; certificate content is not uploaded.