public string ToHexString()
{
var arr = new byte[32];
BitConverter.GetBytes(first).CopyTo(arr, 0);
BitConverter.GetBytes(second).CopyTo(arr, 8);
BitConverter.GetBytes(third).CopyTo(arr, 16);
BitConverter.GetBytes(fourth).CopyTo(arr, 24);
return BitConverter.ToString(arr).Replace("-", "");
}