PseudoShield

Pseudonymize personal data before pasting into AI — 100% local browser extension (Chrome & Firefox).

PseudoShield intercepts paste events (Ctrl+V) on major AI platforms and automatically replaces personal data with deterministic pseudonyms (SHA-256) before the text reaches the chat interface. The AI never sees the real data.

Features

35 detection patterns — names (4 strategies), Belgian NISS, IBAN (7 countries), VAT, BCE, INAMI, emails, phones, addresses, credit cards, IPs, GPS coordinates, social handles
Mathematical validation — Modulo 97 (NISS/IBAN/INAMI), Luhn (credit cards), ISO 13616
GDPR compliance tools — Art. 30 audit journal (CSV/JSON export), Art. 4/Art. 9 categorization, correspondence table
100% local — zero telemetry, no server, no account, Web Crypto API (SHA-256)
6 AI platforms — Claude.ai, ChatGPT, DeepSeek, Gemini, Copilot, Perplexity

How it works

Original text (Ctrl+V)          Pseudonymized text (inserted)
─────────────────────           ─────────────────────────────
Jean-Pierre Dupont        →    [Personne_13]
15/03/1985                →    [Date_1]
85.03.15-123.45           →    [NISS_1]
BE68 5390 0754 7034       →    [IBAN_1]
jp.dupont@lawfirm.be      →    [Email_3]

The extension intercepts the paste, detects PII using regex + validation, replaces with pseudonyms, and inserts the cleaned text. Original data stays in RAM only — never written to disk.

Supported platforms

| Platform | Domain | Adapter | |----------|--------|---------| | Claude | claude.ai | ProseMirror | | ChatGPT | chatgpt.com | ProseMirror | | DeepSeek | chat.deepseek.com | Textarea | | Copilot | copilot.microsoft.com | Textarea | | Gemini | gemini.google.com | Quill | | Perplexity | perplexity.ai | Quill |

Installation

Chrome Web Store

Install PseudoShield — free, open source.

Firefox Add-ons (AMO)

Coming soon — pending AMO review.

Manual — Chrome (developer mode)

Clone this repo: git clone https://github.com/MaitreJV/pseudoshield.git
Open chrome://extensions/
Enable "Developer mode" (top right)
Click "Load unpacked" and select the cloned folder
Navigate to any supported AI platform and paste text with personal data

Manual — Firefox (developer mode)

Clone this repo: git clone https://github.com/MaitreJV/pseudoshield.git
Open about:debugging#/runtime/this-firefox
Click "Load Temporary Add-on..."
Select manifest.json in the cloned folder
Navigate to any supported AI platform and paste text with personal data

Project structure

pseudoshield/
├── manifest.json              # Manifest V3
├── content.js                 # Main content script (paste interception)
├── background.js              # Service worker (alarms, cleanup)
├── popup.html/js              # Extension popup (stats, controls)
├── options.html/js            # Settings page (patterns, sites, journal)
├── privacy.html               # GDPR privacy policy
├── adapters/                  # Platform-specific text insertion
│   ├── adapter-prosemirror.js # Claude.ai, ChatGPT
│   ├── adapter-textarea.js    # DeepSeek, Copilot
│   ├── adapter-quill.js       # Gemini, Perplexity
│   ├── adapter-generic.js     # Fallback for other sites
│   ├── adapter-registry.js    # Adapter selection logic
│   └── cursor-manager.js      # Cursor position management
├── anonymizer/                # Detection & pseudonymization engine
│   ├── patterns-eu.js         # EU patterns (NISS, IBAN, VAT, BCE...)
│   ├── patterns-generic.js    # Generic patterns (names, dates, addresses)
│   ├── patterns-digital.js    # Digital patterns (emails, phones, IPs)
│   ├── detector.js            # Pattern matching orchestrator
│   ├── processor.js           # Main processing pipeline
│   ├── pseudonym-engine.js    # SHA-256 pseudonym generation
│   ├── storage-manager.js     # chrome.storage.local management
│   └── rgpd-logger.js         # GDPR Art. 30 audit logging
├── data/                      # Reference data
│   ├── first-names-be-fr.js   # Belgian/French first names dictionary
│   └── false-positive-bigrams.js # Common word pairs to exclude
├── utils/                     # Utilities
│   ├── hash.js                # Web Crypto SHA-256 wrapper
│   ├── clipboard.js           # Clipboard interception
│   ├── debounce.js            # Debounce utility
│   └── site-adapters.js       # Site detection & adapter mapping
├── ui/                        # UI components
│   ├── toast.js               # Notification toasts
│   ├── toast.css              # Toast styles
│   └── popup.css              # Popup styles
├── icons/                     # Extension icons (16/32/48/96/128)
├── _locales/                  # i18n (fr)
└── test/                      # Test suite
    ├── test-patterns.js       # Pattern detection tests
    ├── test-data.js           # Test fixtures
    └── run-node.js            # Node.js test runner

Privacy

No data collection — everything runs locally in your browser
No network requests — the extension makes zero HTTP calls
No accounts — no sign-up, no login, no tracking
Open source — inspect every line of code
7-day retention — automatic cleanup of stored pseudonyms

Full privacy policy: maitrejv.github.io/pseudoshield/privacy.html

Legal note

PseudoShield performs pseudonymization as defined in GDPR Art. 4(5), not anonymization. The correspondence table allows re-identification by the data controller. This tool helps reduce exposure of personal data to third-party AI providers but does not eliminate all GDPR obligations.

Author

Jeoffrey Vigneron — Attorney at the Brussels Bar, AI law specialist

License

MIT

Pseudoshield

Install / Use

README