System Architecture

Mobile Application (Flutter Frontend)

• Cross-platform framework: Single codebase for iOS & Android using Flutter 3.x.

• State management: Riverpod + StateNotifier for predictable state transitions.

• Key security features:

  • Encrypted local storage (using flutter_secure_storage with AES-256).

  • Biometric authentication (Face ID/Touch ID via biometric_storage).

  • Secure enclave usage (where supported) for private key operations.

• Transaction flow:

  • QR code scanning for address input.

  • Gas fee estimation before signing.

  • Real-time transaction tracking via WebSocket.

Backend Services (Python + MongoDB)

• API layer:

  • FastAPI for high-performance REST endpoints.

  • JWT authentication with short-lived tokens.

  • Rate limiting via Redis.

• Database:

  • MongoDB (sharded cluster for scalability).

  • Stores:

    • User preferences.

    • Transaction metadata (not private keys).

    • Audit logs for compliance.

• Security measures:

  • HSM-backed signing for critical operations.

  • IP filtering and DDoS protection via Cloudflare.

Wallet Core (Aptos SDK Integration)

• Key derivation:

  • BIP-39 mnemonic generation (12/24 words).

  • BIP-44 deterministic wallet paths (m/44'/637'/0'/0 for Aptos).

  • Ed25519 key pairs for Aptos compatibility.

• Transaction lifecycle:

  • Raw transaction construction (Aptos ABI encoding).

  • Client-side signing (never exposes private keys).

  • Submission via Supra Chain RPC.

Blockchain Layer (Supra Chain + Move)

• Supra Chain advantages:

  • High TPS (10,000+ transactions per second).

  • Low latency (sub-second finality).

  • EVM compatibility (future-proofing).

• Move smart contracts:

  • Resource-oriented model prevents double-spending.

  • Module-based architecture for reusable components.

  • Formal verification for security guarantees.