/// <summary>
        /// Initial response from server to client.
        /// </summary>
        /// <param name="Client">A NetworkClient instance.</param>
        /// <param name="Packet">A ProcessedPacket instance.</param>
        public static void HandleServerChallenge(NetworkClient Client, ProcessedPacket Packet)
        {
            Console.WriteLine("Client receives encrypted data - test 2");

            ServerPublicKey = Packet.ReadBytes(Packet.ReadByte());
            byte[] EncryptedData = Packet.ReadBytes(Packet.ReadByte());

            AESEncryptor Enc = (AESEncryptor)Client.ClientEncryptor;
            Enc.PublicKey = ServerPublicKey;
            Client.ClientEncryptor = Enc;
            NetworkFacade.Client.ClientEncryptor = Enc;

            ECDiffieHellmanCng PrivateKey = Client.ClientEncryptor.GetDecryptionArgsContainer().AESDecryptArgs.PrivateKey;
            byte[] NOnce = Client.ClientEncryptor.GetDecryptionArgsContainer().AESDecryptArgs.NOnce;

            byte[] ChallengeResponse = StaticStaticDiffieHellman.Decrypt(PrivateKey,
                ECDiffieHellmanCngPublicKey.FromByteArray(ServerPublicKey, CngKeyBlobFormat.EccPublicBlob),
                NOnce, EncryptedData);

            MemoryStream StreamToEncrypt = new MemoryStream();
            BinaryWriter Writer = new BinaryWriter(StreamToEncrypt);
            
            Writer.Write((byte)ChallengeResponse.Length);
            Writer.Write(ChallengeResponse, 0, ChallengeResponse.Length);
            
            Writer.Write(Client.ClientEncryptor.Username);
            Writer.Write((byte)PasswordHash.Length);
            Writer.Write(PasswordHash);
            Writer.Flush();

            Client.SendEncrypted(0x03, StreamToEncrypt.ToArray());

            Console.WriteLine("Test 2: passed!");
        }
        public static void HandleLoginNotify(NetworkClient Client, ProcessedPacket Packet)
        {
            //Should this be stored for permanent access?
            byte[] ServerPublicKey = Packet.ReadBytes(Packet.ReadByte());
            byte[] EncryptedData = Packet.ReadBytes(Packet.ReadByte());

            AESEncryptor Enc = (AESEncryptor)Client.ClientEncryptor;
            Enc.PublicKey = ServerPublicKey;
            Client.ClientEncryptor = Enc;
            NetworkFacade.Client.ClientEncryptor = Enc;

            ECDiffieHellmanCng PrivateKey = Client.ClientEncryptor.GetDecryptionArgsContainer().AESDecryptArgs.PrivateKey;
            byte[] NOnce = Client.ClientEncryptor.GetDecryptionArgsContainer().AESDecryptArgs.NOnce;

            byte[] ChallengeResponse = StaticStaticDiffieHellman.Decrypt(PrivateKey,
                ECDiffieHellmanCngPublicKey.FromByteArray(ServerPublicKey, CngKeyBlobFormat.EccPublicBlob),
                NOnce, EncryptedData);

            MemoryStream StreamToEncrypt = new MemoryStream();
            BinaryWriter Writer = new BinaryWriter(StreamToEncrypt);

            Writer.Write((byte)ChallengeResponse.Length);
            Writer.Write(ChallengeResponse, 0, ChallengeResponse.Length);

            Writer.Write(Client.ClientEncryptor.Username);
            Writer.Write((byte)PlayerAccount.Hash.Length);
            Writer.Write(PlayerAccount.Hash);
            Writer.Flush();

            //Encrypt data using key and IV from server, hoping that it'll be decrypted correctly at the other end...
            Client.SendEncrypted((byte)PacketType.CHALLENGE_RESPONSE, StreamToEncrypt.ToArray());
        }
        public static void OnChallengeRecieved(NetworkClient Client, ProcessedPacket Packet)
        {
            byte[] CResponse = Packet.ReadBytes(Packet.ReadByte());

            if (CResponse.SequenceEqual(ChallengeResponse))
                Console.WriteLine("Received correct challenge response, client was authenticated!");
            else
                Console.WriteLine("Received incorrect challenge response, client was NOT authenticated!");
            string Username = Packet.ReadString();
            Console.WriteLine("Username: " + Username);

            byte[] PasswordHash = Packet.ReadBytes(Packet.ReadByte());
            Client.Disconnect();
        }
        public static void HandleChallengeResponse(NetworkClient Client, ProcessedPacket P)
        {
            PacketStream OutPacket;

            if (P.DecryptedSuccessfully)
            {
                int Length = P.ReadByte();
                byte[] CResponse;

                if (P.BufferLength >= Length)
                    CResponse = P.ReadBytes(Length);
                else
                {
                    //Authentication failed, so send this packet unencrypted.
                    OutPacket = new PacketStream((byte)PacketType.LOGIN_FAILURE_CITY, 0);
                    OutPacket.WriteHeader();
                    OutPacket.WriteUInt16((ushort)(PacketHeaders.UNENCRYPTED + 1));
                    OutPacket.WriteByte(0x03); //Bad challenge response.
                    Client.Send(OutPacket.ToArray());

                    Logger.LogInfo("Sent LOGIN_FAILURE_CITY!");
                    return;
                }

                AESDecryptionArgs DecryptionArgs = Client.ClientEncryptor.GetDecryptionArgsContainer().AESDecryptArgs;

                if (DecryptionArgs.Challenge.SequenceEqual(CResponse))
                {
                    OutPacket = new PacketStream((byte)PacketType.LOGIN_SUCCESS_CITY, 0);
                    OutPacket.WriteByte(0x01);
                    Client.SendEncrypted((byte)PacketType.LOGIN_SUCCESS_CITY, OutPacket.ToArray());

                    Logger.LogInfo("Sent LOGIN_SUCCESS_CITY!");
                }
                else
                {
                    //Authentication failed, so send this packet unencrypted.
                    OutPacket = new PacketStream((byte)PacketType.LOGIN_FAILURE_CITY, 0);
                    OutPacket.WriteHeader();
                    OutPacket.WriteUInt16((ushort)(PacketHeaders.UNENCRYPTED + 1));
                    OutPacket.WriteByte(0x03); //Bad challenge response.
                    Client.Send(OutPacket.ToArray());

                    Logger.LogInfo("Sent LOGIN_FAILURE_CITY!");
                }
            }
            else
            {
                //Authentication failed, so send this packet unencrypted.
                OutPacket = new PacketStream((byte)PacketType.LOGIN_FAILURE_CITY, 0);
                OutPacket.WriteHeader();
                OutPacket.WriteUInt16((ushort)(PacketHeaders.UNENCRYPTED + 1));
                OutPacket.WriteByte(0x03); //Bad challenge response.
                Client.Send(OutPacket.ToArray());

                Debug.WriteLine("HandleChallengeResponse - decryption failed!");
                Logger.LogInfo("Sent LOGIN_FAILURE_CITY!");
            }
        }
        /// <summary>
        /// A client requested login.
        /// </summary>
        /// <param name="Client">NetworkClient instance.</param>
        /// <param name="Packet">ProcessedPacket instance.</param>
        public static void InitialClientConnect(NetworkClient Client, ProcessedPacket Packet)
        {
            Console.WriteLine("Server receives data - test 1");

            PacketStream EncryptedPacket = new PacketStream(0x02, 0);
            EncryptedPacket.WriteHeader();

            ClientPublicKey = Packet.ReadBytes((Packet.ReadByte()));

            AESEncryptor Enc = (AESEncryptor)Client.ClientEncryptor;
            Enc.NOnce = Packet.ReadBytes((Packet.ReadByte()));
            Enc.PublicKey = ClientPublicKey;
            Enc.PrivateKey = ServerPrivateKey;
            Client.ClientEncryptor = Enc;

            //THIS IS IMPORTANT - public key must be derived from private!
            ServerPublicKey = ServerPrivateKey.PublicKey.ToByteArray();

            ChallengeResponse = new byte[16];
            m_Random.GetNonZeroBytes(ChallengeResponse);

            MemoryStream StreamToEncrypt = new MemoryStream();
            BinaryWriter Writer = new BinaryWriter(StreamToEncrypt);
            Writer.Write(ChallengeResponse, 0, ChallengeResponse.Length);
            Writer.Flush();

            byte[] EncryptedData = StaticStaticDiffieHellman.Encrypt(ServerPrivateKey,
                ECDiffieHellmanCngPublicKey.FromByteArray(ClientPublicKey, CngKeyBlobFormat.EccPublicBlob), Enc.NOnce, 
                StreamToEncrypt.ToArray());

            EncryptedPacket.WriteUInt16((ushort)(PacketHeaders.UNENCRYPTED + 
                (1 + ServerPublicKey.Length) + 
                (1 + EncryptedData.Length)));

            EncryptedPacket.WriteByte((byte)ServerPublicKey.Length);
            EncryptedPacket.WriteBytes(ServerPublicKey);
            EncryptedPacket.WriteByte((byte)EncryptedData.Length);
            EncryptedPacket.WriteBytes(EncryptedData);

            Client.Send(EncryptedPacket.ToArray());

            NetworkFacade.Listener.UpdateClient(Client);

            Console.WriteLine("Test 1: passed!");
        }
        public static void HandleChallengeResponse(NetworkClient Client, ProcessedPacket Packet)
        {
            Console.WriteLine("Server receives challenge response - test 3");

            byte[] CResponse = Packet.ReadBytes(Packet.ReadByte());

            if (CResponse.SequenceEqual(ChallengeResponse))
                Console.WriteLine("Received correct challenge response, client was authenticated!");

            string Username = Packet.ReadString();
            Console.WriteLine("Username: "******"Test 3: passed!");
        }
        /// <summary>
        /// Received initial packet from CityServer.
        /// </summary>
        public static void OnLoginNotifyCity(NetworkClient Client, ProcessedPacket Packet)
        {
            LogThis.Log.LogThis("Received OnLoginNotifyCity!", LogThis.eloglevel.info);

            //Should this be stored for permanent access?
            byte[] ServerPublicKey = Packet.ReadBytes(Packet.ReadByte());
            byte[] EncryptedData = Packet.ReadBytes(Packet.ReadByte());

            //            lock (Client.ClientEncryptor)
            //            {
            //                AESEncryptor Enc = (AESEncryptor)Client.ClientEncryptor;
            //                Enc.PublicKey = ServerPublicKey;
            //                Client.ClientEncryptor = Enc;
            //                lock (NetworkFacade.Client)
            //                    NetworkFacade.Client.ClientEncryptor = Enc;
            //            }

            //            ECDiffieHellmanCng PrivateKey = Client.ClientEncryptor.GetDecryptionArgsContainer().AESDecryptArgs.PrivateKey;
            //            byte[] NOnce = Client.ClientEncryptor.GetDecryptionArgsContainer().AESDecryptArgs.NOnce;

            //            byte[] ChallengeResponse = StaticStaticDiffieHellman.Decrypt(PrivateKey,
            //                ECDiffieHellmanCngPublicKey.FromByteArray(ServerPublicKey, CngKeyBlobFormat.EccPublicBlob),
            //                NOnce, EncryptedData);

            MemoryStream StreamToEncrypt = new MemoryStream();
            BinaryWriter Writer = new BinaryWriter(StreamToEncrypt);

            //            Writer.Write((byte)ChallengeResponse.Length);
            //            Writer.Write(ChallengeResponse, 0, ChallengeResponse.Length);
            Writer.Flush();

            //Encrypt data using key and IV from server, hoping that it'll be decrypted correctly at the other end...
            Client.SendEncrypted((byte)PacketType.CHALLENGE_RESPONSE, StreamToEncrypt.ToArray());
        }
        public static void InitialClientConnect(NetworkClient Client, ProcessedPacket P)
        {
            Logger.LogInfo("Received InitialClientConnect!");

            PacketStream EncryptedPacket = new PacketStream((byte)PacketType.LOGIN_NOTIFY_CITY, 0);
            EncryptedPacket.WriteHeader();

            AESEncryptor Enc = (AESEncryptor)Client.ClientEncryptor;

            Enc.PublicKey = P.ReadBytes((P.ReadByte()));
            Enc.NOnce = P.ReadBytes((P.ReadByte()));
            Enc.PrivateKey = NetworkFacade.ServerPrivateKey;
            Client.ClientEncryptor = Enc;

            MemoryStream StreamToEncrypt = new MemoryStream();
            BinaryWriter Writer = new BinaryWriter(StreamToEncrypt);
            Writer.Write(Enc.Challenge, 0, Enc.Challenge.Length);
            Writer.Flush();

            byte[] EncryptedData = StaticStaticDiffieHellman.Encrypt(NetworkFacade.ServerPrivateKey,
                System.Security.Cryptography.ECDiffieHellmanCngPublicKey.FromByteArray(Enc.PublicKey,
                System.Security.Cryptography.CngKeyBlobFormat.EccPublicBlob), Enc.NOnce, StreamToEncrypt.ToArray());

            EncryptedPacket.WriteUInt16((ushort)(PacketHeaders.UNENCRYPTED +
                (1 + NetworkFacade.ServerPublicKey.Length) +
                (1 + EncryptedData.Length)));

            EncryptedPacket.WriteByte((byte)NetworkFacade.ServerPublicKey.Length);
            EncryptedPacket.WriteBytes(NetworkFacade.ServerPublicKey);
            EncryptedPacket.WriteByte((byte)EncryptedData.Length);
            EncryptedPacket.WriteBytes(EncryptedData);

            Client.Send(EncryptedPacket.ToArray());
        }