Senior Developer Required to Build Secure Messaging App

We are looking for an experienced developer or development team to build a secure communication platform under our brand. The solution will include: Standalone mobile applications (Android & iOS) Desktop applications SDK package for integration purposes Private/enterprise deployment options The platform will require strong Admin controls, secure access management, real-time messaging, calling, recording, and multi-device connectivity. Must-Have Features: 1. Desktop & Mobile Connection Users should be able to start their computer, open the mobile app, and scan a barcode/QR code to connect the desktop application, similar to WhatsApp Web. Support desktop, Android, and iOS versions. 2. User Registration & Account Management Users can create accounts using their email address. Users must provide: First Name Last Name User accounts should be created under our brand name. The system should generate a unique username and password. Other users should only see the user's full name. Users should be searchable by their unique username once shared. 3. Secure Key-Based Access System The application must use a unique key-based access system. On application launch, users should see: "Enter Key" "Get Key" Only Admin can create, issue, and manage access keys. The developer should recommend the best architecture for handling multi-device key management. 4. Messaging Features Real-time text messaging between users. File sharing capability. Messages should not be deleted by normal users. Only Admin should have permission to delete messages/conversations. 5. Calling Features App-to-app voice/video calling. Admin-controlled calling permissions. Admin can enable or disable calling between selected users. Some users should be able to call each other, while others should not unless permission is granted by Admin. 6. Group Management Only Admin can create groups. Only Admin can add or remove users from groups. Admin controls group permissions. 7. Recording & Monitoring Features Conversation recording with noise cancellation. Automatic screenshot capture every 10 seconds. Secure storage and access control for recorded data and screenshots. 8. Notifications & Real-Time Updates Push notifications. Real-time message and communication updates. 9. SDK & Deployment Requirements The solution should support: Standalone branded Android and iOS mobile applications. Desktop application. SDK package for future integration. Private/enterprise deployment options. Android APK/private distribution where required. Approved private iOS distribution methods where applicable. The developer should advise on the best deployment architecture considering security, scalability, and platform limitations. Required Technical Experience: The developer should have proven experience with: Android/iOS application development Desktop application development SDK development Real-time messaging systems Voice/video communication systems WebRTC or similar technologies APIs and third-party libraries Push notifications Backend development and database architecture Secure authentication systems Permission-based user management Experience with similar projects is preferred: Messaging applications Enterprise communication tools Multi-device applications Collaboration platforms License/key-based software systems Project Details: Timeline: Flexible – to be discussed based on scope and complexity. Budget: Open to proposals (hourly or fixed price). Location: Remote Contract: Freelance / short-term initially, with NDA and IP protection agreement. Support: Post-launch maintenance, updates, and future improvements will be required. How to Apply: Please send: Portfolio and previous relevant projects Examples of messaging apps, SDKs, key-based systems, or multi-device applications you have developed Your technical experience Recommended technology stack and architecture Estimated timeline Pricing proposal Any suggestions or questions regarding system design, especially: Multi-device connectivity Key management system SDK architecture Private deployment approach