使用iTextSharp PKCS＃7将数字签名应用于PDF

Question

我正在开发一个Windows应用程序，我需要将数字签名签名为PDF文件，因为我使用了以下代码，这对于.pfx和.p12证书非常有用。

代码

using Org.BouncyCastle.Pkcs;
using System.IO;
using iTextSharp.text.pdf;
using iTextSharp.text.pdf.security;

public class DigitalSignaturePDF
{
    public void DigiSignPdf(string sourceDocument,
        string destinationPath,
        Stream privateKeyStream,
        string keyPassword,
        string reason,
        string location,
        bool isVisibleSignature)
    {
        Pkcs12Store pk12 = new Pkcs12Store(privateKeyStream, keyPassword.ToCharArray());
        privateKeyStream.Dispose();

        //then Iterate throught certificate entries to find the private key entry
        string alias = null;
        foreach (string tAlias in pk12.Aliases)
        {
            if (pk12.IsKeyEntry(tAlias))
            {
                alias = tAlias;
                break;
            }
        }
        var pk = pk12.GetKey(alias).Key;

        // reader and stamper
        PdfReader reader = new PdfReader(sourceDocument);

        using (FileStream fout = new FileStream(destinationPath, FileMode.Append, FileAccess.Write))
        {
            using (PdfStamper stamper = PdfStamper.CreateSignature(reader, fout, '\0'))
            {
                // appearance
                PdfSignatureAppearance appearance = stamper.SignatureAppearance;
                //appearance.Image = new iTextSharp.text.pdf.PdfImage();
                appearance.Reason = reason;
                appearance.Location = location;
                if (isVisibleSignature)
                {
                    appearance.SetVisibleSignature(new iTextSharp.text.Rectangle(20, 10, 170, 60), reader.NumberOfPages, null);
                }
                // digital signature
                IExternalSignature es = new PrivateKeySignature(pk, "SHA-256");
                MakeSignature.SignDetached(appearance, es, new Org.BouncyCastle.X509.X509Certificate[] { pk12.GetCertificate(alias).Certificate }, null, null, null, 0, CryptoStandard.CMS);

                stamper.Close();
            }
        }
        reader.Close();
        reader.Dispose();
    }
}

现在我需要为.p7b（pkcs＃7）文件准备相同的代码，任何人都可以使用pkcs＃7证书签署pdf文件。