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+# Note Locking with Biometrics/PIN - Technical Specification
+
+## Implementation Plan
+1. Use OS-level biometric APIs (Windows Hello, macOS TouchID, Android Biometric)
+2. PIN fallback with secure local storage
+3. AES-256 encryption for note content
+4. React Native or Flutter for cross-platform
+
+## Security Considerations
+- Keys stored in OS keychain/keystore
+- Rate limiting on PIN attempts
+- Auto-lock after inactivity
+
+## Estimated Effort: 2-3 weeks