PAdES PDF Signature Inspector

Checks it performs. For each signature and document timestamp in the file it checks that the signed byte range is well-formed, recomputes the hash of the signed bytes and compares it with the digest inside the signature, and verifies the signature value with the signer's certificate embedded in the file, using your browser's cryptography. It also reports whether the signature covers the whole file or whether bytes follow the signed range (which is normal when validation data or a timestamp was added later, and also what an edit after signing looks like; the tool cannot tell which).

Information it extracts. The signature type (PAdES / CAdES-based, Adobe PKCS#7 detached, or an RFC 3161 document timestamp), the digest algorithm (SHA-1 is flagged as weak), the signer's name field, reason and location as written in the file, the signing time the signer wrote, the signer certificate (subject, issuer, serial, validity period, key type and size), the chain built from certificates embedded in the file, any qualified-certificate statements inside the certificate (shown as a claim in the certificate, not a verified fact), the signature time-stamp token if there is one (its time, the issuing time-stamp authority and whether it matches), and the validation data stored in the document security store (DSS dictionary of the PDF).

PAdES indicators. PAdES is the ETSI profile family for PDF signatures (EN 319 142-1) with levels B-B, B-T, B-LT and B-LTA. The tool reports which building blocks are present: a CAdES sub-filter and signing-certificate attribute for B-B, a signature time-stamp for B-T, certificates and revocation data in the DSS dictionary for B-LT, a later document timestamp for B-LTA. These are indicators of what the file contains; they are not a conformance test.

What it does not do. It does not look up the EU trusted lists, does not decide whether a certificate or its issuer is trusted, qualified or advanced, does not validate the full certificate chain against any root store, does not query revocation services (OCSP, CRL) or judge whether the embedded revocation data is sufficient, and does not judge whether changes after signing are permitted. It does not read XAdES, ASiC or other non-PDF signature formats.

Why not the European Commission DSS. DSS, the open-source Java library of the European Commission (release 6.5 at the time of writing), can validate PAdES signatures against trusted lists. It needs a Java server and, on a website, would mean uploading your PDF to that server, which this site's browser-only tools deliberately avoid. This tool therefore stays a local inspector. For a legally relevant assessment use a validator built for it, such as the DSS demonstration web application or your national validation service.

PDF files up to 50 MB with signatures using CMS/PKCS#7 or CAdES containers (sub-filters adbe.pkcs7.detached and ETSI.CAdES.detached) and RFC 3161 document timestamps (ETSI.RFC3161), with SHA-1, SHA-256, SHA-384 or SHA-512 digests. RSA keys are covered by the automated tests of this tool; ECDSA signatures are attempted but are not covered by them. Encrypted PDFs are not opened. XML and other signature formats (XAdES, ASiC) are not covered.

1. Drag in the signed PDF. It is read in your browser.
2. For each signature, read the status line first: intact, modified, invalid or unreadable. "Intact" is a technical statement about the signed bytes only.
3. Look at the signer certificate and the chain. A self-signed signer or an incomplete chain is flagged.
4. Check the timestamp and DSS sections to see whether long-term validation data is present.
5. If the result matters legally, repeat the check with a trust-aware validator.

• Checking quickly that a contract PDF was not changed after it was signed
• Seeing who signed and with what certificate before you open a more thorough validation
• Finding out whether a file contains a timestamp or long-term validation data
• Telling a real digital signature from a picture of a signature
• Diagnosing why a signature shows as invalid in another viewer

Technical inspection, not legal certification. "Intact" means the signed bytes match and the signature value verifies with the embedded certificate. It does not mean the signature is legally valid, that the signer is who the certificate says, or that the certificate is trusted. No trusted-list evaluation, full chain validation or revocation check is performed.

The chain is built only from certificates embedded in the file; if an intermediate certificate is missing the chain is reported as incomplete, and even a complete chain ending at an embedded self-signed root says nothing about whether that root deserves trust. Qualified-certificate statements are read from the certificate and are claims, not trust-list results. Certificate validity is compared with the signing time claimed in the file, or with the timestamp when there is one; a claimed time is not independently proven.