// (c) 2006 Richard Grimes
// www.grimes.demon.co.uk

using System;
using System.Security.Cryptography;
using System.Net;
using System.Net.Sockets;
using System.Text;

class Alice
{
   static void Main(string[] args)
   {
      if (args.Length == 0) return;
      TcpClient client = new TcpClient();
      client.Connect(IPAddress.Loopback, 5000);
      NetworkStream stm = client.GetStream();
      if (args[0].ToLower() == "quit")
      {
         byte[] quit = Encoding.ASCII.GetBytes(args[0]);
         stm.Write(quit, 0, quit.Length);
         client.Close();
         return;
      }
      byte[] buf = Encoding.ASCII.GetBytes("KEY");
      stm.Write(buf, 0, buf.Length);
      byte[] readBuf = new byte[client.ReceiveBufferSize];
      int read = stm.Read(readBuf, 0, readBuf.Length);
      string reply = Encoding.ASCII.GetString(readBuf, 0, read);
      if (reply.ToLower() == "ack")
      {
         CspParameters csp = new CspParameters(1, null, "Bob");
         RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(csp);
         RSACryptoServiceProvider rsaBobPubKey = new RSACryptoServiceProvider();
         rsaBobPubKey.ImportParameters(rsa.ExportParameters(false));

         RSAPKCS1KeyExchangeFormatter exch = new RSAPKCS1KeyExchangeFormatter();
         exch.SetKey(rsaBobPubKey);
         Rijndael session = Rijndael.Create();
         byte[] key = exch.CreateKeyExchange(session.Key);
         stm.Write(key, 0, key.Length);
         read = stm.Read(readBuf, 0, readBuf.Length);
         reply = Encoding.ASCII.GetString(readBuf, 0, read);
         if (reply.ToLower() == "ack")
         {
            stm.Write(session.IV, 0, session.IV.Length);
            read = stm.Read(readBuf, 0, readBuf.Length);
            reply = Encoding.ASCII.GetString(readBuf, 0, read);
            if (reply.ToLower() == "ack")
            {
               CryptoStream cryptostm = new CryptoStream(stm, session.CreateEncryptor(), CryptoStreamMode.Write);
               byte[] data = Encoding.ASCII.GetBytes(args[0]);
               cryptostm.Write(data, 0, data.Length);
               cryptostm.FlushFinalBlock();
               cryptostm.Clear();
            }
         }
      }
      client.Close();
   }
}