XamarinChatNugget 1.0.1

Here’s a README.md you can drop into your NuGet project repo — written for developers discovering your package:

# XamarinChatNugget 📦🔐

End-to-End Encrypted (E2EE) Messaging library for **Xamarin.Forms / .NET Standard 2.0**.  
Built on [Sodium.Core](https://www.nuget.org/packages/Sodium.Core/) (libsodium crypto), [Xamarin.Essentials](https://learn.microsoft.com/xamarin/essentials/), and [sqlite-net-pcl](https://github.com/praeclarum/sqlite-net).

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## ✨ Features

- 🔑 Identity key pair (X25519) auto-generated & stored securely (Keychain / Keystore).  
- 🔐 End-to-end encryption (ECDH + XSalsa20-Poly1305).  
- 🔄 Ephemeral keys per message for forward secrecy.  
- 📦 Payload contains ciphertext, nonce, and ephemeral public key.  
- 📲 Secure storage of own + peer public keys.  
- 💾 Optional persistence layer with SQLite (swap for SQLCipher in prod).  
- 🛠 Extensible transport (SignalR, WebSockets, REST).

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## 📦 Installation

Add via NuGet:

```bash
dotnet add package XamarinChatNugget

Perfect 👍 let’s extend your README.md so it clearly explains how to set up Firebase Authentication + Realtime Database for your XamarinChatNugget NuGet.

Here’s a structured version you can drop into your repo:

XamarinChatNugget

A demo NuGet package for building secure peer-to-peer chat apps with:

• 🔐 End-to-End Encryption (libsodium)
• ☁️ Firebase Authentication (user accounts)
• 📡 Firebase Realtime Database (public key directory)

🚀 Features

• Secure key generation and storage (private key stays on device).
• Public key exchange via Firebase.
• Simple Auth (signup & login).
• Works in Xamarin.Forms (Android/iOS).

🛠 Setup Guide

1. Create Firebase Project

1. Go to Firebase Console.

2. Create a new project.

3. Enable Authentication → Email/Password.

4. Enable Realtime Database.

   • Set rules to testing mode first:

     {
       "rules": {
         ".read": true,
         ".write": true
       }
     }
     

2. Get API Key & Database URL

• API Key:

  • Go to Project Settings → General → Web API Key.

• Database URL:

  • Go to Realtime Database → Data → URL, e.g.:

    https://your-project-id.firebaseio.com/
    

3. Secure Your Database Rules

Once auth works, update rules to restrict writes:

{
  "rules": {
    "keys": {
      "$userId": {
        ".read": "auth != null",
        ".write": "auth.uid === $userId"
      }
    }
  }
}

✅ This ensures each user can only write their own public key.

4. Install NuGet

In your Xamarin project:

dotnet add package XamarinChatNugget

Or via Visual Studio → Manage NuGet Packages.

5. Initialize in App.xaml.cs

public partial class App : Application
{
    public static AuthService Auth { get; private set; }
    public static FirebaseKeyService KeyService { get; private set; }

    public App()
    {
        InitializeComponent();

        // Replace with your Firebase project values
        Auth = new AuthService("<YOUR_FIREBASE_API_KEY>");
        KeyService = new FirebaseKeyService(
            "https://your-project-id.firebaseio.com/",
            () => Auth.IdToken
        );

        MainPage = new LoginPage();
    }
}

6. User Signup / Login

// Sign up new user
await App.Auth.SignUpAsync("user@example.com", "password123");

// Or login
await App.Auth.LoginAsync("user@example.com", "password123");

// Generate and upload keys
var keyPair = Sodium.PublicKeyBox.GenerateKeyPair();
await App.KeyStore.StoreOwnKeysAsync(App.Auth.UserId, keyPair);
await App.KeyService.UploadKeyAsync(App.Auth.UserId, keyPair.PublicKey);

7. Fetch Peer’s Public Key

var bobPublicKey = await App.KeyService.GetKeyAsync("bob_uid");
await App.KeyStore.StorePeerPublicKeyAsync("bob_uid", bobPublicKey);

8. Encrypt & Send Message

var payload = await App.Crypto.EncryptForAsync("bob_uid", Encoding.UTF8.GetBytes("Hello Bob!"));

Send payload.Ciphertext, payload.Nonce, and payload.EphemeralPublicKey via your transport layer (SignalR/WebSocket/etc).

9. Decrypt on Receiver Side

var plaintextBytes = await App.Crypto.DecryptWithEphemeralAsync("alice_uid", payload);
var plaintext = Encoding.UTF8.GetString(plaintextBytes);

✅ Next Steps

• Add UI pages (Login, Chat).
• Replace dummy transport with SignalR / REST / WebSocket.
• Use SQLCipher if you need encrypted local storage.
• Add device pairing (QR codes) for real apps.

⚡ You now have a secure Firebase-backed chat foundation in Xamarin!

📜 License

MIT License © 2025 YourName

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