C#/VB.NET: Add or Remove Digital Signatures in PowerPoint

A digital signature is a modern alternative to signing documents manually on paper with pen. It uses an advanced mathematical technique to check the authenticity and integrity of digital documents, which guarantees that the contents in a digital document comes from the signer and has not been altered since then. Sometimes PowerPoint documents that contain confidential information may require a signature. In this article, you will learn how to programmatically add or remove digital signatures in PowerPoint using Spire.Presentation for .NET.

Install Spire.Presentation for .NET

To begin with, you need to add the DLL files included in the Spire.Presentation for.NET package as references in your .NET project. The DLL files can be either downloaded from this link or installed via NuGet.

PM> Install-Package Spire.Presentation

Add a Digital Signature to PowerPoint in C# and VB.NET

To add a digital signature, you'll need to have a valid signature certificate first. Then you can digitally sign a PowerPoint document with the certificate using Presentation.AddDigitalSignature (X509Certificate2 certificate, string comments, DateTime signTime) method. The detailed steps are as follows.

  • Create a Presentation instance.
  • Load a sample PowerPoint document using Presentation.LoadFromFile() method.
  • Initializes an instance of X509Certificate2 class with the certificate file name and password.
  • Add a digital signature to the PowerPoint document using Presentation.AddDigitalSignature (X509Certificate2 certificate, string comments, DateTime signTime) method.
  • Save result document using Presentation.SaveToFile() method.
  • C#
  • VB.NET
using Spire.Presentation;
using System;
using System.Security.Cryptography.X509Certificates;

namespace AddDigitalSignature
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Presentation instance
            Presentation ppt = new Presentation();

            //Load a PowerPoint document
            ppt.LoadFromFile("input.pptx");

            //Load the certificate
            X509Certificate2 x509 = new X509Certificate2("gary.pfx", "e-iceblue");

            //Add a digital signature
            ppt.AddDigitalSignature(x509, "e-iceblue", DateTime.Now);

            //Save the result document
            ppt.SaveToFile("AddDigitalSignature.pptx", FileFormat.Pptx2013);
        }
    }
}

C#/VB.NET: Add or Remove Digital Signatures in PowerPoint

Remove All Digital Signatures from PowerPoint in C# and VB.NET

At some point you may need to remove the digital signatures from a PowerPoint document. Spire.Presentation for .NET provides the Presentation.RemoveAllDigitalSignatures() method to remove all digital signatures at once. The detailed steps are as follows:

  • Create a Presentation instance.
  • Load a sample PowerPoint document using Presentation.LoadFromFile() method.
  • Determine if the document contains digital signatures using Presentation.IsDigitallySigned property.
  • Remove all digital signatures from the document using Presentation.RemoveAllDigitalSignatures() method.
  • Save the result document using Presentation.SaveToFile() method.
  • C#
  • VB.NET
using Spire.Presentation;

namespace RemoveDigitalSignature
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Presentation instance
            Presentation ppt = new Presentation();

            //Load a PowerPoint document 
            ppt.LoadFromFile("AddDigitalSignature.pptx");

            //Detect if the document is digitally signed
            if (ppt.IsDigitallySigned == true)
            {
                //Remove all digital signatures
                ppt.RemoveAllDigitalSignatures();
            }

            //Save the result document
            ppt.SaveToFile("RemoveDigitalSignature.pptx", FileFormat.Pptx2013);

        }
    }
}

C#/VB.NET: Add or Remove Digital Signatures in PowerPoint

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