gistfile1.cs

            MemoryStream stream = new MemoryStream();
            try
            {
                m_packets.Clear();

                int count = m_packetCount;
                if (count > 0)
                    m_packets.Capacity = count;

                RawChunkHeader header;
                LinkedList<ChunkHeaderWrapper> headers = new LinkedList<ChunkHeaderWrapper>();

                int i = 0;
                while (count == 0 && !m_fileReader.IsRead() || ++i <= count)
                {
                    header = m_fileReader.ReadStruct<RawChunkHeader>();

                    m_fileStream.Position += header.OptionalDataLength;

                    headers.AddLast(new ChunkHeaderWrapper { m_header = header, m_position = stream.Position });
                    var tmp = m_fileReader.ReadBytes(Math.Min(header.DataLength, (int)m_fileReader.GetRemainingLength()));
                    stream.Write(tmp, 0, tmp.Length);

                    if (progress != null)
                        progress(m_fileStream.Position, m_fileStream.Length);
                }

                var descr = GetDescriptor();
                var opcEnum = descr.OpcodeEnumType;
                var authChallengeValue = (uint)opcEnum.GetField("SMSG_AUTH_CHALLENGE").GetRawConstantValue();
                var authSessionValue = (uint)opcEnum.GetField("CMSG_AUTH_SESSION").GetRawConstantValue();
                var contSessValue = (uint)opcEnum.GetField("CMSG_AUTH_CONTINUED_SESSION").GetRawConstantValue();
                var challengeType = Type.GetType(opcEnum.Namespace + ".OpcodeDatas.AuthChallenge");
                //var challengeSeed = challengeType.GetField("Seed");
                var challengeClientSeed = challengeType.GetField("ClientSeed");
                var challengeServerSeed = challengeType.GetField("ServerSeed");
                //uint seed = 0;
                byte[] ClientSeed = null;
                byte[] ServerSeed = null;
                var cryptToClient = new WowCrypt(Direction.ToClient);
                var cryptToServer = new WowCrypt(Direction.ToServer);

                byte[] chunkHdr = new byte[3 + 4];
                var node = headers.First;
                stream.Position = 0;
                while (!stream.IsRead())
                {
                    while (node.Next != null && node.Next.Value.m_position <= stream.Position)
                        node = node.Next;

                    var direction = node.Value.m_header.Direction;
                    var ticks = node.Value.m_header.TickCount;

                    int SizeLength = 2;
                    int Size = 0;
                    int OpcodeLength = (direction == Direction.ToServer) ? 4 : 2;
                    uint Opcode = 0;

                    bool large = (stream.ReadByte() & 0x80) != 0;
                    --stream.Position;
                    if (large)
                        SizeLength += 1;

                    stream.Read(chunkHdr, 0, SizeLength + OpcodeLength);

                    (direction == Direction.ToClient ? cryptToClient : cryptToServer).Process(chunkHdr, 0, SizeLength + OpcodeLength);

                    // Size includes OpcodeLength, but doesn't include SizeLength.
                    for (int j = 0; j < SizeLength; ++j)
                        Size = (Size << 8) | (int)(chunkHdr[i++] & (j == 0 ? 0x7F : 0xFF));

                    for (int j = 0; j < OpcodeLength; ++j)
                        Opcode |= (uint)chunkHdr[i++] << (j * 8);

                    byte[] data = new byte[Size - OpcodeLength];
                    stream.Read(data, 0, Size - OpcodeLength);

                    if (Opcode == authChallengeValue)
                    {
                        using (var _stream = new MemoryStream(data))
                        using (var _reader = new BinaryReader(_stream))
                        {
                            var challenge = Activator.CreateInstance(challengeType, _reader);
                            //seed = (uint)challengeSeed.GetValue(challenge);
                            ClientSeed = (byte[])challengeClientSeed.GetValue(challenge);
                            ServerSeed = (byte[])challengeServerSeed.GetValue(challenge);
                        }
                    }
                    else if (Opcode == authSessionValue)
                    {
                        cryptToClient.Init(SessionKey, null);
                        cryptToServer.Init(SessionKey, null);
                    }
                    else if (Opcode == contSessValue)
                    {
                        cryptToClient.Init(SessionKey, ClientSeed);
                        cryptToServer.Init(SessionKey, ServerSeed);
                    }

                    var wowPacket = new WowPacket(data, direction,
                        PacketFlags.None, Opcode,
                        (StartedOnUnix + (ticks - StartedOnTicks) / 1000).AsUnixTime(),
                        ticks,
                        Size - OpcodeLength, node.Value.m_header.ConnectionId);
                    m_packets.Add(wowPacket);

                    if (callback != null)
                        callback(wowPacket);
                }
            }
            catch (Exception e)
            {
                System.Windows.Forms.MessageBox.Show(e.ToString());
                throw;
            }
            finally
            {
                stream.Close();
                CloseFile();
            }

can post the cryptToClient class ?