how to verify the digital signature with modem code 52 in Windows 7

I use Aspose.Cells to add digital signature, and it works fine

using Aspose.Cells;
using Aspose.Cells.DigitalSignatures;
using System.Security.Cryptography.X509Certificates;

       public void testSign()
       {
           DigitalSignatureCollection dsc = new DigitalSignatureCollection();
           //mykey.pfx is author's private key , "tryto" is password of private key.
           X509Certificate2 cert = new X509Certificate2("m:\\mykey.pfx", "tryto");
           DigitalSignature ds = new DigitalSignature(cert, "helloworld", DateTime.Now);
           dsc.Add(ds);
           Workbook wb = new Workbook("m:\\test.xlsx");
           wb.AddDigitalSignature(dsc);
           wb.Save("m:\\test.xlsx");
       }

Validate file:
       public void testvalidateSign()
       {
           Workbook wb = new Workbook("m:\\test.xlsx");
           System.Console.WriteLine(wb.IsDigitallySigned);
           DigitalSignatureCollection dsc = wb.GetDigitalSignature();
           foreach (DigitalSignature ds in dsc)
           {
               System.Console.WriteLine(ds.Comments);
               System.Console.WriteLine(ds.SignTime);
               System.Console.WriteLine(ds.IsValid);
           }
           System.Console.ReadLine();
       }

If this is after you’ve created your account, you can navigate away from that webpage and go to mail.google.com and sign in (bypassing the verification process). This is what I did, I’m not sure if it still works though. 

use Aspose.Cells to add or get digital signature, and it works fine for me .

using Aspose.Cells;
using Aspose.Cells.DigitalSignatures;
using System.Security.Cryptography.X509Certificates;

       public void testSign()
       {
           DigitalSignatureCollection dsc = new DigitalSignatureCollection();
           //mykey.pfx is author's private key , "tryto" is password of private key.
           X509Certificate2 cert = new X509Certificate2("m:\\mykey.pfx", "tryto");
           DigitalSignature ds = new DigitalSignature(cert, "helloworld", DateTime.Now);
           dsc.Add(ds);
           Workbook wb = new Workbook("m:\\test.xlsx");
           wb.AddDigitalSignature(dsc);
           wb.Save("m:\\test.xlsx");
       }

Validate file:
       public void testvalidateSign()
       {
           Workbook wb = new Workbook("m:\\test.xlsx");
           System.Console.WriteLine(wb.IsDigitallySigned);
           DigitalSignatureCollection dsc = wb.GetDigitalSignature();
           foreach (DigitalSignature ds in dsc)
           {
               System.Console.WriteLine(ds.Comments);
               System.Console.WriteLine(ds.SignTime);
               System.Console.WriteLine(ds.IsValid);
           }
           System.Console.ReadLine();
       }