public int Decrypt(Internal.CommunicationStream message, int offset = 0, int length = int.MaxValue) { length = Math.Min(length, (int)message.Length - offset); length -= length % BlockSize; int i = offset; while (i < offset + length) { message.Position = i; uint v0 = message.ReadUnsignedInt(); uint v1 = message.ReadUnsignedInt(); uint delta = 0x61C88647; uint sum = 0xC6EF3720; for (int r = 0; r < 32; r++) { v1 -= (v0 << 4 ^ v0 >> 5) + v0 ^ sum + _key[sum >> 11 & 3]; sum += delta; v0 -= (v1 << 4 ^ v1 >> 5) + v1 ^ sum + _key[sum & 3]; } message.Position -= BlockSize; message.WriteUnsignedInt(v0); message.WriteUnsignedInt(v1); i += BlockSize; } message.Position = offset; int payloadLength = message.ReadUnsignedShort(); int messageLength = payloadLength + Internal.Connection.PacketLengthSize; int lengthDelta = messageLength - length; if (lengthDelta > 0 || -lengthDelta > length) { return(0); } message.SetLength(message.Length + lengthDelta); return(length); }