Product Requirements: Secure Communication App¶
1. Product Vision¶
To provide a simple, reliable, and exceptionally secure communication tool where users can make private video and audio calls, confident that call media content is protected from server-side and network-intermediary eavesdropping.
2. Core User Features¶
The app will deliver a focused set of features to ensure a high-quality, secure calling experience.
| Feature | Description |
|---|---|
| Secure 1-to-1 Calls | Users can make crystal-clear, private video and audio calls to another user. |
| Secure Group Calls | Users can create and participate in group video and audio calls with the same level of security as 1-to-1 calls. |
| Call History | Users can view a history of their past calls (incoming, outgoing, missed). |
| Rejoin Active Calls | If a user is disconnected from an ongoing call, they can easily rejoin it from their call history. |
| Contact Management | Users can manage a list of contacts within the app for quick and easy calling. |
| Simple Authentication | Users can sign up and log in easily using their email, phone number, or existing Apple/Google accounts. |
3. Security & Privacy: The Core Promise¶
The fundamental principle of this app is that call media content is private and cannot be decrypted by the company. This is achieved through a security model called End-to-End Encryption (E2EE).
How It Works (In Simple Terms)¶
- Your Device Holds the Key: When you sign up, your device creates a unique digital "key" that is stored securely on the device itself. This key never leaves your phone.
- Locked Conversations: Every call (video, audio) is "locked" using these keys. Only the devices of the people in the call have the keys to "unlock" and listen to the conversation.
- No Middleman Access to Media Content: The call media travels through managed transport, but it remains encrypted end-to-end. The backend cannot decrypt or listen to call media content.
- Per-Session Security: Every call uses a fresh AES-256 session key generated on device. The active key can be rotated from the in-call key manager when needed.
Security Outcomes¶
- Strong Content Privacy: Call media is encrypted so only participating devices should be able to play it.
- No Server Media Access: The company and its infrastructure should not be able to decrypt call media content.
- Hardware-Level Protection: On iPhones, the user's primary digital key is protected by the device's Secure Enclave, a specialized hardware security component.
- Resilience: The system is designed to recover from temporary media reconnect issues while preserving the active call encryption state.