# Features

## Core Features

| Feature                      | Description                                                  |
| ---------------------------- | ------------------------------------------------------------ |
| **Signal Protocol**          | X3DH + Double Ratchet for all messages                       |
| **Decentralized Network**    | No central server — data distributed across validator nodes  |
| **3-Hop Onion Routing**      | RSA-4096 per-hop routing for traffic analysis resistance     |
| **Zero-Knowledge Proofs**    | Anonymous authentication via Groth16 RLN                     |
| **Post-Quantum Crypto**      | Hybrid Kyber-768 + X25519 for quantum-resistant key exchange |
| **No Phone Number Required** | Sign in with Web3 wallet — MetaMask, WalletConnect, etc.     |
| **Progressive Web App**      | Install on any device, works offline                         |
| **GDPR/HIPAA/SOC3**          | Enterprise compliance frameworks                             |

***

## Messaging

All messages are encrypted end-to-end with Signal Protocol before leaving your device.

* **Text messages** with editing (48-hour window with full history)
* **Voice messages** with waveform visualization
* **Message reactions** with any emoji
* **Reply & quote** functionality
* **Message forwarding** to multiple contacts
* **Message deletion** (for yourself or everyone)
* **Disappearing messages** — auto-delete timers from 5 seconds to 1 week
* **Pinned messages** with navigation banner
* **Starred messages** — encrypted mesh storage for favorites
* **Read receipts & delivery status** (optional, encrypted)
* **Typing indicators** (optional, encrypted)
* **Link previews** — sender-generated, privacy-preserving
* **Contact sharing** — vCard format with one-tap actions
* **Chat export** — export full chat histories
* **Message search** across all conversations

***

## Voice & Video Calls

All signaling is encrypted with the Double Ratchet. Media streams are peer-to-peer via WebRTC.

* **1-on-1 calls** — voice and video, direct peer-to-peer
* **Group calls** — up to 6 participants with full mesh P2P topology
* **Screen sharing** in both 1-on-1 and group calls
* **Echo cancellation, noise suppression, automatic gain control**
* **Picture-in-picture mode**
* **Call history** — encrypted on mesh, not on server

***

## Groups & Channels

### Groups

* Encrypted group chats with role-based access (Owner, Admin, Member)
* Public and private groups with invite links
* Group membership hidden from relays
* Automatic key rotation on member removal
* **Sealed Group Fanout** — privacy-preserving delivery where relays never enumerate members

### Channels

* Broadcast channels for one-to-many communication
* Public or private with subscriber management
* Role & permission management

***

## Media & Files

* **Images** — JPEG, PNG, WebP with auto-compression
* **Videos** — MP4 with thumbnails
* **Audio** — MP3, WAV, OGG
* **Documents** — any file type
* **GIFs** — privacy-preserving mesh delivery (sender fetches and encrypts)
* **Stickers** — encrypted pack management
* **Built-in image editor** — canvas editor for photos before sending
* Large files chunked via **Reed-Solomon erasure coding** across mesh nodes

***

## Stories

* Encrypted 24-hour ephemeral content
* Per-viewer access control (ECDH per-viewer encryption)
* Viewer tracking
* Auto-cleanup after expiration

***

## Polls & Location

* **Polls** — encrypted in groups and channels, server cannot see questions or votes
* **Location sharing** — static and live with auto-expiration
* **Maps** — OpenStreetMap integration (privacy-first, no Google)

***

## Privacy & Metadata Protection

Zentalk goes beyond message encryption to protect your communication patterns:

| Protection              | Implementation                              |
| ----------------------- | ------------------------------------------- |
| Address Hashing         | SHA-256 hashed addresses                    |
| Conversation ID Privacy | Hashed sorted address pairs                 |
| Encrypted Routing       | Sender/recipient inside E2EE payload        |
| Encrypted Presence      | Online/offline status encrypted             |
| Stealth Addresses       | Ephemeral ECDH keypair per message          |
| Cover Traffic           | Dummy requests during idle periods          |
| Message Padding         | Uniform sizes (512, 1024, 4096, 8192 bytes) |
| Fuzzy Presence          | Delayed/batched status updates              |

***

## Identity & Authentication

### Wallet-Based (Primary)

* MetaMask, WalletConnect, or any Web3 wallet
* No password required — authentication via wallet signature
* Multi-chain: Ethereum, Arbitrum, Base, Sepolia

### Phone-Based (Alternative)

* Phone number + SMS verification code
* Keys derived deterministically (PBKDF2-SHA512, 600K iterations)
* Phone deleted after verification, only hash stored in mesh DHT

### Usernames

* Unique usernames stored in mesh DHT
* Ed25519 signed entries prevent DHT poisoning
* Privacy-preserving lookups (username hashed as DHT key)

***

## Security Features

* **Multi-factor authentication** — TOTP + WebAuthn (hardware keys)
* **Active sessions management** — view and revoke sessions across devices
* **Safety number verification** — verify contact identity
* **Encrypted blocked/muted lists**
* **Multi-language support** (i18n)
* **Customizable keyboard shortcuts**
* **Dark/light themes** with custom wallpapers
* **Network topology visualization**

***

## Node Infrastructure

### Running a Validator Node

| Requirement | Detail                                |
| ----------- | ------------------------------------- |
| Stake       | 5,000 CHAIN tokens                    |
| Hardware    | 4 cores, 8 GB RAM, 500 GB SSD         |
| Network     | Public IP address required            |
| Software    | Single binary (`./bin/relay`)         |
| Setup       | Minutes with Docker or install script |

### Node Performance

Benchmarked on Apple M3 Pro:

| Operation                   | Speed     | Throughput        |
| --------------------------- | --------- | ----------------- |
| AES-256-GCM Encrypt         | 1.7 us/op | 590K ops/s        |
| RSA-4096 Encrypt            | 206 us/op | 4.8K ops/s        |
| 3-Hop Relay Encrypt         | 603 us/op | 1.6K ops/s        |
| Message Relay               | —         | 1,000+ msg/s/node |
| Storage Write               | —         | 100+ MB/s         |
| 3-Hop Routing Latency (p95) | <100ms    | —                 |
| Concurrent Connections      | —         | 10,000+ per node  |

### Monitoring

* 40+ Prometheus metrics
* Grafana dashboards for real-time monitoring
* OpenTelemetry distributed tracing
* Health endpoints (DHT, storage, peers, memory)
* SIEM integration (Splunk, ELK, QRadar)

***

## Technical Stack

### Frontend

| Technology           | Purpose              |
| -------------------- | -------------------- |
| Next.js 16           | Framework            |
| React 19             | UI Library           |
| TypeScript 5         | Language             |
| Zustand              | State Management     |
| TanStack React Query | Async Data           |
| Tailwind CSS 4       | Styling              |
| Radix UI             | Component Primitives |
| Zod 4                | Schema Validation    |

### Backend (Go 1.24)

| Technology        | Purpose                  |
| ----------------- | ------------------------ |
| libp2p            | P2P, DHT, GossipSub, NAT |
| PostgreSQL 16     | Metadata & Profiles      |
| Redis             | Caching & Sessions       |
| Gorilla WebSocket | Real-time Communication  |
| Reed-Solomon      | Erasure Coding           |
| cloudflare/circl  | PQC (Kyber, Dilithium)   |
| consensys/gnark   | Zero-Knowledge Proofs    |
| Prometheus        | Monitoring               |

### Cryptography (Client)

| Library        | Purpose                     |
| -------------- | --------------------------- |
| Web Crypto API | Hardware-accelerated crypto |
| @noble/curves  | Ed25519/X25519              |
| @noble/hashes  | SHA-256, HMAC, HKDF         |
| mlkem          | Kyber-768 (ML-KEM FIPS 203) |
| viem           | Ethereum wallet interaction |