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Excel Digital Signatures

Hi Aspose,

I am working with a client who requires that I send him an excel file that is digitally signed. I have successfully prototyped a solution using Aspose.Cells and been able to send him a .xlsx file. Unfortunately his users do not have Excel 2007 available on their desktops and when I attempt to save a signed Aspose.Cells.Workbook to FileFormatType.Excel97To2003 the signature gets removed.

Is there any way using your component, to save a signed workbook in a format earlier than Excel 2007 .xslx?

Best Regards,

Hi,


Please check the document:
http://www.aspose.com/documentation/.net-components/aspose.cells-for-.net/assign-and-validate-digital-signatures.html

If you find any issue, kindly do create a sample console application to show the issue with all the files. We will check it soon.

We recommend you to try our latest version/fix: Please download: Aspose.Cells for .NET v7.0.0.1

Hello and thanks for the reply. Here is an example (using your own code) where the digital signing fails. I have tried this with both the 6.1 and the v7.0.01 that you linked to:

using System;
using System.IO;
using Aspose.Cells;
using System.Collections;
using System.Text;
using System.Threading;
using Aspose.Cells.Rendering;
using System.Security.Cryptography;
using System.Diagnostics;
using Aspose.Cells.DigitalSignatures;
using System.Security.Cryptography.X509Certificates;

namespace Aspose.Cells.test
{


class MyTest
{

public MyTest()
{
}



[STAThread]
static void Main(string[] args)
{

MyTest test = new MyTest();
test.testSign();
test.testvalidateSign();
Console.ReadLine();

}



internal void testvalidateSign()
{

Workbook wb = new Workbook(@“c:\newfile.xls”);
System.Console.WriteLine(wb.IsDigitallySigned); //True -OK
DigitalSignatureCollection dsc = wb.GetDigitalSignature();

foreach (DigitalSignature ds in dsc)
{
System.Console.WriteLine(ds.Comments); //test for sign -OK
System.Console.WriteLine(ds.SignTime); //11/25/2010 1:22:01 PM -OK
System.Console.WriteLine(ds.IsValid); //True -OK
}

}

internal void testSign()
{

DigitalSignatureCollection dsc = new DigitalSignatureCollection();

DigitalSignature ds = new DigitalSignature(
FindCertificateFromSerial(“5d 88 3d d1 ab 8d 63 c2 eb 64 c2 fc 8a e7 fb bd”),
“test for sign”, DateTime.Now);

dsc.Add(ds);

Workbook wb = new Workbook();
wb.SetDigitalSignature(dsc);
wb.Save(@“c:\newfile.xls”, SaveFormat.Excel97To2003);

}

public static X509Certificate2 FindCertificateFromSerial(string serialNum)
{
X509Store localStore = new X509Store(StoreName.My, StoreLocation.CurrentUser);
localStore.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);
try
{
X509Certificate2Collection matches =
localStore.Certificates.Find(X509FindType.FindBySerialNumber, serialNum, false);
if (matches.Count > 0)
return matches[0];
else
return null;


}
finally
{ localStore.Close(); }
}

}

}

This code works perfectly for the Xslx format, but fails for Xls.

Hi,


Thanks for sharing the sample code.

I have logged your issue with an id: CELLSNET-30247. We will look into your issue soon.

Thank you.

Hi,

As mentioned in release notes, we only support adding digital signature on Ms-Excel 2007 or later formats. We will support it for Ms-Excel 2003 formats in later release versions.

Hi,
Is checking digital signature (Workbook.IsDigitallySigned) on Ms-Excel 2003 supported in the latest version (XLS files)?

Regards

@bar678,

Yes, Aspose.Cells does support digital signatures for XLS file format. Please try using our latest version/fix (Aspose.Cells v21.5.x). If you find any issue, kindly zip and share your sample digitally signed MS Excel 2003 XLS file, we will look into it soon.