Creating a secure channel

using System.Text;
using VSSProtocol.DataLayer;
using VSSProtocol.Session;
using System;

namespace VSSProtocol.Messages
{
	/// <summary>
	/// Master key message contains an encryption of the master key. This message uses the session values that where
	/// defined during the ClientHello messages. Pay attention to the fact that both constructors do the opposite work...one
	/// encypted (client) and one decryptes (server).
	/// </summary>
	internal class ClientKeyExchangeMessage : DataPacket
	{
		/// <summary>
		/// The premaster key that was chosen. Decrypted.
		/// </summary>
		private readonly String preMasterKey;
		/// <summary>
		/// Create a new ClientKeyExchange message.
		/// </summary>
		/// <param name="session">Session to use in order to retreive the public encryption algorithm.</param>
		/// <param name="preMasterKey">From this string all keys will be derived.</param>
		public ClientKeyExchangeMessage(ISession session, String preMasterKey)
			: base(PacketTypeEnum.ClientKeyExchange)
		{
			if (preMasterKey == null || session == null)
			{
				throw new ArgumentNullException();
			}
			this.preMasterKey = preMasterKey;
			// Prepare data byte array.
			byte[] preMasterByte = Encoding.ASCII.GetBytes(preMasterKey);
			// We can compress now the premaster key (compressing at the data layer will be useless) but I'll skip it.
			setData(session.AsymmetricAlgorithm.Encrypt(preMasterByte));
		}

		/// <summary>
		/// Create a new ClientKeyExchange message. The message contains the encrypted values of the premaster key.
		/// </summary>
		/// <param name="session">Session to use in order to retreive the public encryption algorithm.</param>
		/// <param name="message">Message to convert.</param>
		public ClientKeyExchangeMessage(ISession session, byte[] message)
			: base(PacketTypeEnum.ClientKeyExchange)
		{
			setData(message);
			// First decrypt.
			byte[] decryptedPreMaster = session.AsymmetricAlgorithm.Decrypt(message);
			// Get string value.
			preMasterKey = Encoding.ASCII.GetString(decryptedPreMaster);
		}


		/// <summary>
		/// The premaster key that was chosen. Decrypted.
		/// </summary>
		public string PreMasterKey
		{
			get { return preMasterKey; }
		}
	}
}