• Hybrid RSA-AES-GCM encryption system (crypto_utils.dart)
• Secure storage service with production upgrade path (storage_service.dart)
• Updated dependencies and configuration (pubspec.yaml)
• Comprehensive integration guide (integration_guide.md)
• Test utilities for validation (test_utils.dart)
• Complete documentation (README.md)

• RSA-2048 key generation with secure random seeding
• AES-256-GCM authenticated encryption
• OAEP padding for RSA operations
• SHA-256 digital signatures for authentication
• Ephemeral AES keys for forward secrecy
• Device fingerprinting with SHA-256
• Secure key serialization format

• RSA key generation and operations
• AES-GCM encryption/decryption
• Digital signature verification
• Hybrid encryption round-trip testing
• Key serialization/deserialization
• Storage persistence testing
• Performance benchmarking
• Security validation (tampering detection)

• Replace SharedPreferences with flutter_secure_storage
• Enable Android Keystore / iOS Keychain integration
• Add biometric authentication for private key access
• Implement key rotation mechanisms
• Add perfect forward secrecy (Double Ratchet)
• Conduct professional security audit
• Perform penetration testing

• Implement native Android services:
  • ZappOverlayService for system overlay
  • ZappAccessibilityService for content capture
  • Method channel communication
• Add required Android permissions to manifest
• Test on multiple Android versions (API 23+)
• Verify overlay functionality across device manufacturers

• Implement "tiny infra" relay server
• Design message relay protocol
• Add OTP verification system for device linking
• Implement rate limiting and abuse prevention
• Add message delivery confirmation
• Set up monitoring and logging

• Implement background key generation
• Add message chunking for large content
• Optimize AES-GCM operations
• Add caching for frequently used keys
• Implement efficient message queuing

• Add comprehensive onboarding flow
• Implement proper error handling and user feedback
• Add progress indicators for cryptographic operations
• Design intuitive device management interface
• Add accessibility features

• Privacy policy covering E2EE and data handling
• Terms of service with security disclaimers
• GDPR compliance assessment
• Export control compliance (cryptography regulations)
• Security incident response plan

• Production server deployment
• SSL/TLS certificates for API endpoints
• Database security and encryption at rest
• Backup and disaster recovery procedures
• Monitoring and alerting systems

• Log analysis for security events
• Intrusion detection systems
• Regular security assessments
• Vulnerability scanning
• Incident response procedures

• End-to-end testing on production environment
• Load testing for server infrastructure
• Security testing with production configuration
• User acceptance testing
• Beta testing with selected users

• Google Play Store compliance review
• App signing with production keys
• Release notes and documentation
• Support documentation for users
• Customer support procedures

• Regular security updates
• Cryptographic library updates
• Security monitoring and analysis
• Periodic security audits
• Vulnerability assessment and patching

• iOS client implementation
• Desktop client support
• Group messaging functionality
• File transfer capabilities
• Advanced privacy features

• Performance metrics collection
• Usage analytics (privacy-preserving)
• Error tracking and reporting
• User feedback collection
• Security metrics and KPIs

• Private Keys: Must be stored in hardware-backed security modules
• Message Storage: Minimize temporary storage, implement secure deletion
• Metadata: Protect against traffic analysis and timing attacks
• Backup: Secure key backup and recovery procedures

• Device Compromise: Private keys protected by hardware security
• Network Attacks: All communication encrypted end-to-end
• Server Compromise: Zero knowledge - server cannot access plaintext
• Quantum Threats: Plan for post-quantum cryptography migration

• GDPR: Data minimization, user consent, right to deletion
• Regional Laws: Compliance with local encryption regulations
• Export Controls: Cryptography export compliance
• Industry Standards: NIST, OWASP, security frameworks

# Run all cryptographic tests
flutter test test/crypto_test.dart

# Performance benchmarks  
flutter test test/performance_test.dart --enable-asserts

# Integration tests
flutter test integration_test/

// In your app's debug mode
final testPassed = await CryptoTestSuite.runAllTests();
print('All tests passed: \$testPassed');

# Static analysis
flutter analyze

# Dependency vulnerabilities
flutter pub deps --json | dart security_scanner.dart

# Code quality
dart format --set-exit-if-changed .

1. Immediate: Disable affected services
2. Assessment: Evaluate impact and scope
3. Containment: Prevent further compromise
4. Recovery: Restore secure operations
5. Communication: Notify affected users
6. Post-mortem: Analyze and improve

1. Immediate key rotation for affected devices
2. Revoke compromised certificates
3. Audit message history for potential exposure
4. User notification with remediation steps
5. Enhanced monitoring for suspicious activity

• Zero successful cryptographic attacks
• 100% message authenticity verification
• < 1% key generation/encryption failures
• < 100ms encryption latency for 10KB messages

• < 5 seconds device linking time

• 95% user satisfaction with security

• < 2% support requests related to encryption

• 99.9% message delivery success rate

⚠️ IMPORTANT: This checklist is comprehensive but not exhaustive. Security is an ongoing process requiring continuous attention, regular updates, and professional expertise. Consult security professionals before production deployment.