Protect PowerPoint PPTX in C#

protect-pptx-digital-signature.cs

// Instantiate a Presentation object that represents a presentation file
using (Presentation pres = new Presentation("presentation.pptx"))
{
    // Create DigitalSignature object with PFX file and PFX password 
    DigitalSignature signature = new DigitalSignature("testsignature1.pfx", @"testpass1");

    // Comment new digital signature
    signature.Comments = "Aspose.Slides digital signing test.";

    // Add digital signature to presentation
    pres.DigitalSignatures.Add(signature);

    // Save presentation
    pres.Save("signed-presentation.pptx", Export.SaveFormat.Pptx);
}

protect-pptx-password.cs

// Instantiate a Presentation object that represents a presentation file
using (Presentation pres = new Presentation("presentation.pptx"))
{
    // Protect with password
    pres.ProtectionManager.Encrypt("password");

    // Save presentation
    pres.Save("protected-presentation.pptx", Export.SaveFormat.Pptx);
}

verify-pptx-digital-signature.cs

// Instantiate a Presentation object that represents a presentation file
using (Presentation pres = new Presentation("presentation.pptx"))
{
    // Check if presentation has digital signatures
    if (pres.DigitalSignatures.Count > 0)
    {
        bool allSignaturesAreValid = true;

        Console.WriteLine("Signatures used to sign the presentation: ");

        // Check if all digital signatures are valid
        foreach (DigitalSignature signature in pres.DigitalSignatures)
        {
            Console.WriteLine(signature.Certificate.SubjectName.Name + ", "
                    + signature.SignTime.ToString("yyyy-MM-dd HH:mm") + " -- " + (signature.IsValid ? "VALID" : "INVALID"));
            allSignaturesAreValid &= signature.IsValid;
        }

        if (allSignaturesAreValid)
            Console.WriteLine("Presentation is genuine, all signatures are valid.");
        else
            Console.WriteLine("Presentation has been modified since signing.");
    }
}