Document Sealer
Document Sealer Logo
🔐 Cryptographic Document Integrity for Google Workspace™

Does Your Google Doc™ Still Match
Your Printed Copy?

With Document Sealer, you'll always know for certain. Embed a tamper-evident cryptographic seal (QR code + verification code) directly into your Google Docs™ footer or Google Sheets™ tab. Anyone holding the printed copy can instantly verify whether the live cloud version still matches the sealed version.

🚀 Explore How It Works 🛡️ Zero-Server Security Architecture
🛡️ Zero External Servers
🔒 SHA-256 + HMAC-SHA256 Signing
👁️ Independent Verification for Viewers
⚡ 100% Free Verification for Everyone
🌐 Zero Quota / Zero Third-Party API Limits
🕒 Unambiguous UTC Timestamps

Why Paper Alone Cannot Defend Itself

The fundamental reason verification must anchor to the live Google Doc™ or Google Sheet™

⚠️ The Physical Paper Dilemma

A printed piece of paper has no hardware root of trust. Anyone with Photoshop, high-res scanning, or a color printer can modify clauses, dates, or prices on a printed sheet while keeping an authentic QR code perfectly intact. Scanning a paper-only QR code only verifies the data inside the code—it cannot physically read the surrounding paper.

✅ The Document Sealer Solution

Document Sealer anchors the cryptographic fingerprint of your live Google Doc or Google Sheet at the exact second it was printed. Anyone holding the printed copy can input the seal code or scan the QR code into the document verifier: the system recalculates the math on the live cloud document to confirm whether it remains bit-for-bit unchanged.

🔐 How It Works

Three effortless steps to cryptographic integrity across both Google Docs™ and Google Sheets™

1

Seal

Document Sealer extracts your document contents and computes a SHA-256 fingerprint, then signs it with HMAC-SHA256 using your account's private key.

  • Runs 100% inside your Google account
  • Zero bytes sent to third-party servers
  • Generates an 8-character code (e.g. A3B7-K9M2)
2

Print

The seal appears seamlessly right where you need it, ready for printing or exporting as an audit-ready PDF:

  • Google Docs™: Embedded directly in the document footer with high-density QR & metadata.
  • Google Sheets™: Inserted as a dedicated, pristine "Document Sealer Seal" tab.
3

Verify

Verification takes seconds and is always 100% free with no license required:

  • Open the sidebar → Verify Current Document for instant one-click check.
  • Or scan the printed QR code / type the 8-character verification code from the physical paper.

✅ Instant Verification Results

Unambiguous, mathematical proof of document status in plain language

✅

Document Is Current

The seal signature is authentic, and the live document content is 100% unchanged since sealing. The printed copy perfectly matches the cloud document.

⚠️

Document Has Changed

The seal is authentic and recognized, but the document was edited after it was sealed. The viewer is immediately alerted to cloud drift or unauthorized edits.

🚫

Invalid Signature

The seal signature does not match. The seal may have been forged, tampered with, or originated from an unauthorized installation.

📌

No Seal Found

This document has not been sealed yet. Open the Seal tab to generate an authentic cryptographic seal.

👁️ Empowering Read-Only Viewers

In standard Google Workspace™, "Version History" and revision tracking are strictly restricted to Editors and Owners. Users with View-Only access have zero native way of knowing whether an editor silently modified a contract clause, price list, or financial figure.

Document Sealer eliminates this blind spot. Because verification only requires read access, clients, employees, contractors, and external auditors can verify document integrity without needing editor rights or access to private revision history.

Google Docs™ Native Version History for Viewers ❌ Blocked
Ability to Detect Changes Without Editor Rights ❌ None
Document Sealer Verification for Viewers ✅ 100% Supported
License Required to Verify Documents ✅ Completely Free ($0)

🚀 Key Features

Designed for mission-critical workflows with zero overhead and complete privacy

🛡️

Zero External Servers

All cryptographic hashing and HMAC signing run natively inside Google Apps Script. Your confidential document content never leaves Google's encrypted infrastructure.

⚡

Zero Quota & Zero Limits

Uses built-in Google Apps Script cryptographic utilities (Utilities.computeDigest and Utilities.computeHmacSha256Signature). No third-party API limits or per-document fees.

🔄

Unified Docs™ & Sheets™

Enjoy a unified, consistent experience across both Google Docs™ and Google Sheets™ with the exact same dark-mode sidebar panel and verification logic.

📱

QR Code + 8-Char Short Code

Every seal includes both a high-density QR code for instant smartphone camera scanning and a paper-safe 8-character code (e.g. A3B7-K9M2) that excludes ambiguous characters.

🕒

Unambiguous UTC Timestamps

All seal records and displays use Coordinated Universal Time (UTC) to eliminate timezone discrepancies across international legal, compliance, and accounting teams.

✨

Always-Free Verification

Verification requires NO license and is always 100% free for everyone. Recipients, viewers, clients, and auditors never have to pay to verify seals.

🔒 Security & Privacy Architecture

Built from the ground up for strict corporate compliance and data sovereignty

Layer Implementation Privacy & Security Guarantee
Content Hashing SHA-256 (NIST FIPS 180-4) If even a single comma or character changes, the fingerprint changes completely.
Digital Signature HMAC-SHA256 with 256-bit auto-generated secret Secret key is securely stored in Google's encrypted ScriptProperties.
Data Transmission Zero external network calls for hashing/verification Document content NEVER leaves your Google account.
OAuth Scopes documents.currentonly, spreadsheets.currentonly Only accesses the currently open file. Cannot read your broader Google Drive™.
Verification Math 100% Local inside Apps Script runtime Verifications run without external API dependencies.

💡 Perfect For Every Industry

Ensuring compliance, authenticity, and confidence across critical operations

⚖️ Legal & Compliance

Keep audit-ready physical printouts of NDAs, contracts, and settlement agreements with indisputable tamper-evident seals.

📊 Finance & Accounting

Seal invoices, quarterly financial statements, and balance sheets before sending physical copies to auditors or banks.

👥 HR & People Operations

Distribute verified employment contracts, offer letters, and policy handbooks with verifiable digital anchors.

🎓 Academic & Research

Certify published research data exports, lab test results, transcripts, and grade sheets against retrospective tampering.

📋 Transparent Licensing

Free verification forever. Flexible sealing licenses for creators and teams.

✔ Verification is Always Free ($0)

Document Sealer Annual License

Unlimited document sealing for Google Docs™ & Sheets™

  • ✅ Full Google Workspace™ Add-on for Docs & Sheets
  • ✅ 3-Day Free Trial included with zero commitment
  • ✅ Unlimited sealing across all your documents
  • ✅ Unlimited free verifications for all recipients and viewers
  • ✅ Step-by-step setup & license activation guide
  • ✅ All future updates and improvements included

Securely processed via Gumroad. License keys are delivered instantly via email.

❓ Frequently Asked Questions

Everything you need to know about Document Sealer

Do recipients, clients, or viewers need a license to verify? +
No! Verification is 100% free and never requires a license. Anyone with access to the document or holding a printed copy can verify seals at zero cost. Only sealing (creating and inserting new seals) requires an active license or trial.
Can I use this across multiple documents? +
Yes! Once activated, your license allows unlimited sealing across all your Google Docs and Google Sheets.
Is my document content ever shared or uploaded to external servers? +
Never. Document Sealer runs entirely inside your Google account via Google Apps Script. All hashing, signing, and verification happen within Google's secure perimeter. Only your license key is verified against Gumroad's API once every 24 hours.
What happens if a user with View-Only access tries to insert a seal? +
Google Workspace strictly enforces access control. If a viewer tries to insert a seal, the add-on recognizes their permissions and informs them politely that only document editors or owners can insert seals into the file. No invalid seal is ever saved.
What if I lose my license key? +
You can retrieve your key anytime at gumroad.com/license-key-lookup using the email address you purchased with.

Technical Support & Feedback

We're dedicated to helping you protect your documents with cryptographic confidence.

For questions, support, or partnership inquiries regarding Document Sealer:

✉️ numbrate@gmail.com

Document Sealer: Cryptographic Document Integrity for Google Workspace

Document Sealer is an enterprise-grade Google Workspace add-on for Google Docs and Google Sheets that calculates SHA-256 cryptographic digests of document contents and signs them with HMAC-SHA256 signatures. It inserts QR codes and 8-character verification codes into document footers and spreadsheet tabs. It enables tamper-evident physical printouts, independent verification for read-only viewers, and zero-server security.