Mobile · Security2026
Secure Vault Offline
Secure, offline-first portfolio tracker built in Flutter with SQLCipher AES-256 database encryption, biometric session lock, and background isolate-based XIRR yield calculations.
- Role
- Solo engineer — security architecture, cryptography, offline engine
- Timeline
- 2026
- Stack
- FlutterDartSQLCipherAES-256IsolatesBiometricsSQLite
01
Screens & Architecture
02
The Problem
Financial asset trackers often transmit sensitive portfolio data over cloud servers or lack zero-knowledge local encryption, creating privacy vulnerabilities and slow analytics on large transaction logs.
03
How I built it
- SQLCipher AES-256 Encryption: Encrypted all local portfolio databases on disk using zero-knowledge SQLCipher hardware keys.
- Biometric Session Lock: Built automatic biometric authentication triggers (Face ID / Fingerprint) on app backgrounding and idle timeouts.
- Isolate-Based XIRR Engine: Offloaded heavy financial yield calculations and XIRR mathematical solvers to background Dart isolates to maintain 60 FPS UI.
- FIFO Offline Mutation Queue: Implemented an offline mutation queue with exponential backoff retries for safe transaction history replay.
04
Outcome
- Achieved military-grade zero-knowledge local data privacy with zero unencrypted portfolio leaks.
- Maintained butter-smooth 60 FPS UI performance during complex multi-year portfolio yield calculations using Dart isolates.