# Certificate Checker

> Analyze and extract signatures and certificates from executable files (.exe, .efi) or certificate files.

- Open in browser: https://pockettoolbox.org/en/certificate-extractor
- Runs entirely in your browser; files and input are never uploaded.

## How it works

Analyze and extract digital signatures and X.509 certificates.

Upload a file (.exe, .efi, .cer, etc.). For PE executables, the embedded signature is located in the security directory and decoded to display issuer, validity, serial number, and fingerprints.

PE parsing: Reads the DOS header magic ("MZ"), parses the PE offset (e_lfanew at 0x3C), locates IMAGE_DATA_DIRECTORY[4] (Security Directory) and extracts the embedded PKCS#7/CMS DER blob. This is deserialized using asn1js + pkijs. X.509 certificate data (Issuer, Validity, SubjectPublicKeyInfo) is read from the ASN.1 structures and rendered as text. DER/PEM uploads are processed directly via pkijs.Certificate.fromBER().

---
PocketToolbox (https://pockettoolbox.org/en)