# SMOA System Architecture

**Version:** 1.0  
**Last Updated:** 2024-12-20  
**Status:** Draft - In Progress

---

## System Overview

The Secure Mobile Operations Application (SMOA) is a hardened Android-based application designed for deployment on approved foldable mobile devices. SMOA enables identity presentation, secure internal routing, and mission communications in connected, disconnected, and degraded environments.

### System Purpose
SMOA provides secure mobile operations capabilities for government and military personnel, including:
- Digital credential presentation
- Secure communications
- Orders management
- Evidence chain of custody
- Regulatory reporting
- Domain-specific operations (law enforcement, military, judicial, intelligence)

### System Context
SMOA operates in a secure mobile and multi-platform environment with:
- **Primary client:** Android (enterprise-hardened builds); primary device class foldable smartphones with biometric hardware support.
- **Additional clients:** iOS (last three generations: iOS 15, 16, 17) and Web Dapp (Desktop/Laptop, including touch devices); same backend API contract.
- **Deployment Model:** Government-furnished or government-approved devices under MDM/UEM control where applicable; Web Dapp served over HTTPS with CORS.
- **Connectivity:** Online, offline, and degraded modes; backend supports all clients via REST and configurable CORS.

---

## Architecture Principles

### Security First
- Multi-factor authentication required
- Hardware-backed encryption
- Zero-trust architecture principles
- Defense in depth

### Resilience
- Offline operation capability
- Degraded mode support
- Data synchronization
- Automatic recovery

### Compliance
- Standards-based implementation
- Compliance by design
- Audit trail throughout
- Certification ready

### Modularity
- Modular architecture
- Clear module boundaries
- Well-defined interfaces
- Reusable components

---

## High-Level Architecture

### System Components

```
┌─────────────────────────────────────────────────────────────┐
│                    SMOA Application                          │
├─────────────────────────────────────────────────────────────┤
│                                                               │
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐       │
│  │   Core       │  │   Core       │  │   Core       │       │
│  │   Modules    │  │   Modules    │  │   Modules    │       │
│  │   (8)        │  │   (8)        │  │   (8)        │       │
│  └──────────────┘  └──────────────┘  └──────────────┘       │
│                                                               │
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐       │
│  │   Feature    │  │   Feature    │  │   Feature    │       │
│  │   Modules    │  │   Modules    │  │   Modules    │       │
│  │   (13)       │  │   (13)       │  │   (13)       │       │
│  └──────────────┘  └──────────────┘  └──────────────┘       │
│                                                               │
│  ┌──────────────────────────────────────────────────────┐  │
│  │         Common Infrastructure                         │  │
│  │  - Authentication  - Security  - Database            │  │
│  │  - Networking     - Storage   - Logging             │  │
│  └──────────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────────────┘
```

### Core Modules (8)
1. **core:auth** - Authentication framework
2. **core:security** - Security infrastructure
3. **core:common** - Common utilities
4. **core:barcode** - PDF417 barcode generation
5. **core:as4** - AS4 gateway messaging
6. **core:eidas** - eIDAS compliance
7. **core:signing** - Digital signatures & seals
8. **core:certificates** - Certificate management

### Feature Modules (13)
1. **modules:credentials** - Issued credentials
2. **modules:directory** - Internal directory
3. **modules:communications** - Unit communications
4. **modules:meetings** - Secure meetings
5. **modules:browser** - Controlled browser
6. **modules:orders** - Orders management
7. **modules:evidence** - Evidence chain of custody
8. **modules:reports** - Report generation
9. **modules:atf** - ATF form support
10. **modules:ncic** - NCIC/III integration
11. **modules:military** - Military operations
12. **modules:judicial** - Judicial operations
13. **modules:intelligence** - Intelligence operations

---

## Component Architecture

### Authentication Component
- Multi-factor authentication (PIN + Fingerprint + Facial Recognition)
- Session management
- Re-authentication triggers
- Hardware-backed key storage

### Security Component
- Encryption (at rest and in transit)
- Key management
- Certificate management
- Audit logging
- Policy enforcement

### Data Storage Component
- Room database (local SQLite)
- Encrypted storage
- Offline data caching
- Data synchronization

### Network Component
- Secure communication (TLS)
- VPN support
- Offline mode detection
- Degraded mode handling

---

## Module Architecture

### Module Structure
Each module follows a consistent structure:
- **Domain Layer:** Business logic and data models
- **Data Layer:** Database and repositories
- **Presentation Layer:** UI components (Jetpack Compose)
- **Service Layer:** Business services

### Module Dependencies
- Core modules have no dependencies on feature modules
- Feature modules depend on core modules
- Clear dependency hierarchy
- Minimal inter-module dependencies

---

## Data Architecture

### Data Model
- **Room Database:** Primary local storage
- **Encrypted Storage:** Sensitive data encryption
- **Offline Cache:** Time-bounded offline data
- **Synchronization:** Data sync on connectivity

### Data Flow
1. User input → Domain layer
2. Domain layer → Data layer (persistence)
3. Data layer → Domain layer (retrieval)
4. Domain layer → Presentation layer (display)

### Data Protection
- Encryption at rest (hardware-backed)
- Encryption in transit (TLS)
- Access control (RBAC)
- Audit logging

---

## Integration Architecture

### External System Integrations
- **AS4 Gateway:** Inter-agency messaging
- **NCIC/III:** Law enforcement databases
- **ATF eTrace:** Firearms tracing
- **QTSP:** Qualified Trust Service Providers
- **Timestamping Authority:** Qualified timestamps

### Integration Patterns
- RESTful APIs
- AS4 messaging
- Secure file transfer
- Certificate-based authentication

---

## Deployment Architecture

### Deployment Model
- **Device:** Government-furnished foldable Android devices
- **MDM/UEM:** Mobile device management
- **Backend Services:** Enterprise backend (if applicable)
- **Network:** Secure government networks

### Infrastructure Requirements
- Android 7.0+ (API 24+)
- Biometric hardware support
- Hardware-backed key storage
- Network connectivity (with offline support)

---

## Technology Stack

### Platform
- **Language:** Kotlin
- **Platform:** Android
- **Minimum SDK:** 24 (Android 7.0)
- **Target SDK:** 34 (Android 14)

### Core Libraries
- **UI:** Jetpack Compose
- **Database:** Room
- **Networking:** Retrofit, OkHttp
- **Dependency Injection:** Hilt
- **Security:** Android Keystore, BouncyCastle
- **Barcode:** ZXing
- **PDF:** PDFBox or iText

### Development Tools
- **IDE:** Android Studio
- **Build System:** Gradle
- **Version Control:** Git
- **CI/CD:** (To be determined)

---

## Security Architecture

See [Security Architecture Document](SECURITY_ARCHITECTURE.md) for detailed security architecture.

### Key Security Features
- Multi-factor authentication
- Hardware-backed encryption
- Secure key storage
- Encrypted communication
- Audit logging
- Policy enforcement

---

## Performance Considerations

### Optimization Strategies
- Lazy loading
- Caching
- Background processing
- Efficient database queries
- Image optimization

### Performance Targets
- Application startup: < 3 seconds
- Screen transitions: < 300ms
- API response: < 2 seconds
- Database queries: < 100ms

---

## Scalability

### Current Scope
- Single device deployment
- Local data storage
- Offline-first architecture

### Future Considerations
- Multi-device synchronization
- Cloud backend integration
- Enterprise deployment

---

## Diagrams

### System Architecture Diagram
[To be added: PlantUML or image]

### Component Architecture Diagram
[To be added: PlantUML or image]

### Module Dependency Diagram
[To be added: PlantUML or image]

### Data Flow Diagram
[To be added: PlantUML or image]

---

## References

- [Specification](../SPECIFICATION.md)
- [Security Architecture](SECURITY_ARCHITECTURE.md)
- [Implementation Status](../IMPLEMENTATION_STATUS.md)
- [Compliance Matrix](../COMPLIANCE_MATRIX.md)

---

**Document Owner:** Technical Lead  
**Last Updated:** 2024-12-20  
**Status:** Draft - In Progress  
**Next Review:** 2024-12-27