XamarinChatNugget 1.0.0

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).

---

## ✨ 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).

---

## 📦 Installation

Add via NuGet:

```bash
dotnet add package XamarinChatNugget

Or in Visual Studio:

Manage NuGet Packages → Browse → XamarinChatNugget

🚀 Quick Start

1. Initialize in App

using XamarinChatNugget.Services;

public partial class App : Application
{
    public static SodiumKeyStore KeyStore { get; private set; }
    public static SodiumCryptoService Crypto { get; private set; }

    public App()
    {
        InitializeComponent();

        KeyStore = new SodiumKeyStore();
        Crypto = new SodiumCryptoService(KeyStore);

        MainPage = new MainPage();
    }
}

2. Send a Message

var keyStore = App.KeyStore;
var crypto = App.Crypto;

// Store Bob's public key (normally obtained via QR/server)
await keyStore.StorePeerPublicKeyAsync("bob", bobPublicKey);

// Encrypt for Bob
var payload = await crypto.EncryptForAsync("bob", Encoding.UTF8.GetBytes("Hello Bob!"));

// Send payload.Ciphertext + payload.Nonce + payload.EphemeralPublicKey over the network

3. Receive & Decrypt

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

Console.WriteLine($"Decrypted: {plaintext}");

🔐 Key Exchange

• On first contact, users must exchange public keys.

• Options:

  • QR Code scan 📱
  • Server lookup 🌐
  • Invite link 🔗

⚠️ Security Notes

This package demonstrates secure message encryption/decryption. For production apps, you should also add:

• ✅ Auth & user accounts
• ✅ Secure key exchange (QR or authenticated server)
• ✅ SQLCipher for encrypted DB storage
• ✅ Transport layer (SignalR/WebSockets/HTTPS)
• ✅ Push notifications
• ✅ Ratchet protocol (for Signal-style secrecy)

📜 License

MIT License © 2025 YourName

---

👉 Do you want me to also include a **demo screenshot** section with fake chat UI (Alice ↔ Bob) so your NuGet page looks more professional on nuget.org/GitHub?