Question

I am trying to create a unit test that generates an empty test document similar to the one found in the Aspose Words example. I created a test cert using makecert.exe with the following line in the VS Command Promp

makecert.exe -sv MyKey.pvk -n "CN=MY DIGITAL KEY" MyKey.cer

I then converted it to a .pvk file using the following line

pvk2pfx.exe -pvk MyKey.pvk -spc MyKey.cer -pfx MyPFX.pfx

After this was done I copied the .pfx file into my .net console app and set the copy parameter to copy always so that the file is copied to the bin directory when I test the app in debug.

My console app then contains the following lines of code which tries to write a digitally signed pdf.

static void Main()
{
string MyDir = AppDomain.CurrentDomain.BaseDirectory;
// Create a simple document from scratch.
Document doc = new Document();
DocumentBuilder builder = new DocumentBuilder(doc);
builder.Writeln("Test Signed PDF.");
// Load the certificate from disk.
// The other constructor overloads can be used to load certificates from different locations.
X509Certificate2 cert = new X509Certificate2(MyDir + "RpaKey.pfx", "");
Console.WriteLine("Loading certificate...");
// Pass the certificate and details to the save options class to sign with.
PdfSaveOptions options = new PdfSaveOptions();
options.DigitalSignatureDetails = new PdfDigitalSignatureDetails(
cert,
"Test Signing",
"Aspose Office",
DateTime.Now);
Console.WriteLine("Creating digital signature details...");
try
{
// Save the document as PDF with the digital signature set.
doc.Save(MyDir + "Document.Signed Out.pdf", options);
Console.WriteLine("File saved successfully.");
}
catch (Exception ex)
{
Console.WriteLine("File write failed.");
Console.WriteLine(ex.Message);
if (ex.InnerException != null)
{
Console.WriteLine("");
Console.WriteLine(ex.InnerException);
}
}
Console.ReadKey();
}

However I keep getting an “invalid algorith specified” error with no inner exception. Has any one run into this problem? Have I missed a step? Any help is appreciated.

Answer 1

Never used Aspose myself but you should first ensure that your conversion from the PVK to the PFX format worked like you expected.

Change this:

X509Certificate2 cert = new X509Certificate2(MyDir + "RpaKey.pfx", "");
Console.WriteLine("Loading certificate...");

to

X509Certificate2 cert = new X509Certificate2(MyDir + "RpaKey.pfx", "");
Console.WriteLine("Loading certificate... private key available ? {0}", cert.HasPrivateKey);

Note that it likely did success since there was no exception – but that will at least confirm the first part of your process is valid 🙂

If this shows true then you should update your question to show the full stack trace from your exception, e.g.

catch (Exception ex)
{
    Console.WriteLine(ex);
}

so we’ll see if the error comes from Aspose or the BCL itself.