Quiet Paper
An offline-first, privacy-focused Markdown notes application inspired by the calm editorial aesthetic of Bear Notes, featuring zero-knowledge end-to-end encrypted cloud synchronization.
Architecture Overview
- Frontend / Client: Flutter & Dart with Drift SQLite (local offline persistence) and Riverpod state management.
- Backend: TypeScript serverless functions deployed to Vercel (
backend/).
- Cloud Database: Turso / libSQL SQLite-compatible distributed database.
- Authentication: Firebase Authentication for identity and access authorization.
- Cryptography: Client-side Argon2id key derivation and XChaCha20-Poly1305 AEAD authenticated encryption. The backend and cloud database are crypto-blind and never possess plaintext note content or master decryption keys.
Environment Variables & Configuration
1. Backend Environment Variables (backend/.env or Vercel Dashboard)
Copy backend/.env.example to backend/.env:
cp backend/.env.example backend/.env
Set the following variables:
# -------------------------------------------------------------
# Turso / libSQL Database
# -------------------------------------------------------------
# Obtain from https://turso.tech (CLI: turso db show <db-name> --url)
TURSO_DATABASE_URL=libsql://your-database-name.turso.io
# Obtain via: turso db tokens create <db-name>
TURSO_AUTH_TOKEN=your-turso-auth-token
# -------------------------------------------------------------
# Firebase Admin SDK Configuration
# -------------------------------------------------------------
# Obtain from Firebase Console -> Project Settings -> Service Accounts -> Generate New Private Key
FIREBASE_PROJECT_ID=your-firebase-project-id
FIREBASE_CLIENT_EMAIL=firebase-adminsdk-xxx@your-firebase-project-id.iam.gserviceaccount.com
FIREBASE_PRIVATE_KEY="-----BEGIN PRIVATE KEY-----\n...\n-----END PRIVATE KEY-----\n"
# Optional: Port for local testing server
PORT=3000
2. Flutter Client Configuration (--dart-define)
When building or running the Flutter application, pass the Firebase Web API Key and backend sync URL via --dart-define:
flutter run \
--dart-define=FIREBASE_API_KEY=AIzaSy... \
--dart-define=SYNC_API_URL=https://your-vercel-deployment.vercel.app
| Variable | Description | Default |
|---|
FIREBASE_API_KEY | Firebase Web API Key (from Firebase Console -> Project Settings) | "" |
SYNC_API_URL | Base URL of deployed Vercel backend | http://localhost:3000 |
Development & Testing
Backend (TypeScript)
cd backend
npm install
npm test # Run Vitest test suite (13 unit & crypto-blindness tests)
npm run build # Compile TypeScript
Flutter Client
flutter pub get
flutter analyze # Static analysis (0 errors/warnings)
flutter test # Run full test suite (70 tests)
Documentation
