dchain/client-app

DChain Messenger — React Native Client

E2E-encrypted mobile/desktop messenger built on the DChain blockchain stack.

Stack: React Native · Expo · NativeWind (Tailwind) · TweetNaCl · Zustand

Quick Start

cd client-app
npm install
npx expo start          # opens Expo Dev Tools
# Press 'i' for iOS simulator, 'a' for Android, 'w' for web

Requirements

• Node.js 18+
• Expo Go on your phone (for Expo tunnel), or iOS/Android emulator
• A running DChain node (see root README for docker compose up --build -d)

Project Structure

client-app/
├── app/
│   ├── _layout.tsx           # Root layout — loads keys, sets up nav
│   ├── index.tsx             # Welcome / onboarding
│   ├── (auth)/
│   │   ├── create.tsx        # Generate new Ed25519 + X25519 keys
│   │   ├── created.tsx       # Key created — export reminder
│   │   └── import.tsx        # Import existing key.json
│   └── (app)/
│       ├── _layout.tsx       # Tab bar — Chats · Wallet · Settings
│       ├── chats/
│       │   ├── index.tsx     # Chat list with contacts
│       │   └── [id].tsx      # Individual chat with E2E encryption
│       ├── requests.tsx      # Incoming contact requests
│       ├── new-contact.tsx   # Add contact by @username or address
│       ├── wallet.tsx        # Balance + TX history + send
│       └── settings.tsx      # Node URL, key export, profile
├── components/ui/            # shadcn-style components (Button, Card, Input…)
├── hooks/
│   ├── useMessages.ts        # Poll relay inbox, decrypt messages
│   ├── useBalance.ts         # Poll token balance
│   └── useContacts.ts        # Load contacts + poll contact requests
└── lib/
    ├── api.ts                # REST client for all DChain endpoints
    ├── crypto.ts             # NaCl box encrypt/decrypt, Ed25519 sign
    ├── storage.ts            # SecureStore (keys) + AsyncStorage (data)
    ├── store.ts              # Zustand global state
    ├── types.ts              # TypeScript interfaces
    └── utils.ts              # cn(), formatAmount(), relativeTime()

Cryptography

Operation	Algorithm	Library
Transaction signing	Ed25519	TweetNaCl sign
Key exchange	X25519 (Curve25519)	TweetNaCl box
Message encryption	NaCl box (XSalsa20-Poly1305)	TweetNaCl box
Key storage	Device secure enclave	expo-secure-store

Messages are encrypted as:

Envelope {
  sender_pub:    <X25519 hex>   // sender's public key
  recipient_pub: <X25519 hex>   // recipient's public key
  nonce:         <24-byte hex>  // random per message
  ciphertext:    <hex>          // NaCl box(plaintext, nonce, sender_priv, recipient_pub)
}

Connect to your node

1. Start the DChain node: docker compose up --build -d
2. Open the app → Settings → Node URL → http://YOUR_IP:8081
3. If using Expo Go on physical device: your PC and phone must be on the same network, or use npx expo start --tunnel

Key File Format

The key.json exported/imported by the app:

{
  "pub_key":     "26018d40...",   // Ed25519 public key (64 hex chars)
  "priv_key":    "...",           // Ed25519 private key (128 hex chars)
  "x25519_pub":  "...",           // X25519 public key (64 hex chars)
  "x25519_priv": "..."            // X25519 private key (64 hex chars)
}

This is the same format as the Go node's --key flag.