PDF Digital Signature Validator — Verify Certificates Online
Verify PDF digital signatures and cryptographic X.509 certificates online for free. Check signer identity, timestamps, and document integrity locally.
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How Signature Validation Works
Inspect cryptographic integrity, signer certificates, and tampering boundaries in three direct steps.
Load Signed PDF Document
Drop your signed PDF file into the secure validator. The document is decoded in local browser memory without uploading bytes to remote servers.
Parse Cryptographic Envelopes
Our parser extracts /ByteRange arrays, checks for appended byte mutations, and decodes ASN.1 DER certificates, signers, and digest algorithms.
Audit Tamper & Expiry Status
Review validity badges, certificate validity windows, and export a structured JSON audit report verifying legal non-repudiation.
Local Cryptographic Verification vs. Cloud Validators
Why client-side cryptographic parsing guarantees total non-disclosure for sensitive agreements and court filings.
| Feature | Utilvo In-Browser | Cloud Signature Services |
|---|---|---|
| Cryptographic Environment | 100% Client-Side WebAssembly Sandbox | Remote Cloud Virtual Machines |
| Document Confidentiality | Zero server uploads, zero network leakage | Entire signed document transmitted and stored remotely |
| ByteRange Integrity Inspection | Exact byte offset boundaries checked against total file size | Often checks signature metadata without ByteRange tamper audit |
| Certificate Attribute Extraction | Direct ASN.1 DER parser for CN, Org, Email, and Validity | Opaque passes or restricted vendor-only certificate trust lists |
| Exportable JSON Audit Log | Forensic machine-readable audit report generated on demand | Paywalled compliance reports or proprietary log formats |
What Our PDF Signature Validator Checks (PKI, Hash & Timestamps)
How PDF signatures are structured under ISO 32000-2 and ETSI EN 319 142 PAdES standards.
ISO 32000-2 /ByteRange Mathematics
A digital signature cannot sign itself. The /ByteRange array specifies two pairs of byte offsets [offset1, length1, offset2, length2], covering all document bytes except the hexadecimal /Contents signature placeholder. If file size exceeds offset2 + length2, bytes were appended.
ASN.1 DER Certificate Decoding
Within the cryptographic /Contents stream, an ASN.1 DER encoded PKCS#7 or CMS object encapsulates the signer public key certificate, issuer chain, signature timestamp, and signedDigest. Our client-side parser traverses ASN.1 TLV tuples directly.
SubFilter Architecture & PAdES Profiles
The /SubFilter dictionary entry designates the signature profile: adbe.pkcs7.detached, adbe.pkcs7.sha1, or ETSI.CAdES.detached. Modern eIDAS and European PAdES standards mandate ETSI profiles with SHA-256 or higher cryptographic digests.
Post-Signing Modification Detection
When malicious actors or PDF tools modify a signed file, alterations are frequently tacked on via incremental update trailers. The validator flags these changes as MODIFIED_AFTER_SIGNING, protecting recipients from unauthorized contract edits.
How to Spot Tampered or Expired Digital Signatures
Essential verification points when auditing digitally signed PDFs for legal or compliance admissibility.
Inspect Overall Status
Ensure the signature status shows COMPLIANT and VALID rather than MODIFIED_AFTER_SIGNING or INVALID.
Verify Signer Identity
Confirm that the extracted Common Name (CN) and Organization (O) match the designated executing party.
Check Validity Window
Verify that the signing timestamp occurred within the certificate valid date range before expiration.
Save Audit JSON Log
Download the machine-readable audit report to maintain a permanent forensic record for compliance archiving.
PDF Signature Specifications vs Validation Standards
Comparing standard PDF signature formats and cryptographic profiles under international specifications.
| Signature Standard | Specification | SubFilter Key | Digest Algorithm | Role | Best Use Case |
|---|---|---|---|---|---|
| PKCS#7 Detached Signature | ISO 32000-1 / RFC 2315 | adbe.pkcs7.detached | SHA-256 / SHA-512 | Source of this tool | General corporate signing, invoices, and standard agreements |
| Validated Signature Audit | ISO 32000-2 ByteRange | Forensic Integrity Audit | SHA-256 Digest Match | Target of this export | Court submission verification, contract compliance audits |
| PAdES-Baseline Profile | ETSI EN 319 142-1 | ETSI.CAdES.detached | SHA-256 or higher | European eIDAS standard | EU legal transactions, public tenders, and regulated filings |
| PAdES Long-Term (LTV) | ETSI EN 319 142-2 / DSS | Embedded CRL / OCSP | SHA-256 + TimeStamp | Long-term validation | Decade-scale statutory records, patents, and property deeds |
| Legacy SHA-1 PKCS#7 | Adobe PDF 1.3 / Deprecated | adbe.pkcs7.sha1 | SHA-1 (Cryptographically Weak) | Legacy signature | Historical archives requiring migration or re-signing |
| Approval Signature Field | ISO 32000-2 Widget /Sig | AcroForm Signature Field | Visual + Cryptographic | Interactive form sign | Multi-party workflow approvals and purchase order sign-offs |
Frequently Asked Questions
Understand how in-browser cryptographic verification validates ByteRange boundaries, X.509 certificates, and PAdES signatures.
1What does a VALID digital signature status indicate?
A valid status confirms that the digital signature envelope is cryptographically sound, matches the public key certificate, and no modifications have occurred since signing.
2How does the ByteRange integrity check detect tampering?
Under ISO 32000-2 Section 12.8, the ByteRange array defines signed file byte boundaries. If file size exceeds the highest signed byte offset, unauthorized data was appended.
3Can this validator verify signatures conforming to PAdES standards?
Yes. It inspects PKCS#7 (adbe.pkcs7.detached) and ETSI EN 319 142 PAdES signatures, extracting X.509 certificate chains, subfilters, and signing attributes.
4What should I do if a signature status displays MODIFIED_AFTER_SIGNING?
This status indicates incremental revisions or byte insertions were made after document signing. You should treat the file as unverified and request an original signed copy.
5Are my signed documents uploaded to any remote server?
No. All ASN.1 parsing, DER certificate decoding, and ByteRange validation occur strictly inside your browser memory using WebAssembly and JavaScript with zero server uploads.
6What hash algorithms does the validator use to recompute the signed digest?
The validator recomputes SHA-256, SHA-384 and SHA-512 digests over the concatenated /ByteRange byte slices and compares each result to the signedDigest attribute declared in the PKCS#7 envelope, surfacing the matching algorithm in the audit report.
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