public static void EncryptExcelFile(string sourceExcelPath, string destinateExcelPath, string password)
{
Aspose.Cells.Workbook workbook = new Aspose.Cells.Workbook(sourceExcelPath);
workbook.SetEncryptionOptions(Aspose.Cells.EncryptionType.XOR, 40);
workbook.SetEncryptionOptions(Aspose.Cells.EncryptionType.StrongCryptographicProvider, 128);
workbook.Settings.Password = password;
workbook.Save(destinateExcelPath);
}