单个PDF中多个位置的数字签名

Question

我正在使用pdf进行数字签名。我可以在PDF中添加单个签名，但是当我尝试在多个地方添加相同的签名时，我会收到无效签名问题。

我使用下面的代码在多个位置对单个PDF文件进行数字签名，但签名出现在一个地方。

在另一个地方没有显示。（签名无效）。 我在下面使用的是代码

    string dttime = DateTime.Now.ToString("yyyy-MM-ddTHH:mm:ss");
    PdfReader pdfReader = null;
    PdfStamper stamper = null;

    try
    {
    pdfReader = new PdfReader(In_File_Name);
    stamper = PdfStamper.CreateSignature(pdfReader, new FileStream(New_File_Name, FileMode.Create, FileAccess.Write), '\0', null, true);

    //Annotation code for multiple signatures
    PdfSignatureAppearance appearance = stamper.SignatureAppearance;
    appearance.Reason = "";// ConfigurationManager.AppSettings["APPEARANCE_REASON"].ToString();
    appearance.Location = "";// ConfigurationManager.AppSettings["APPEARANCE_LOCATION"].ToString();
    appearance.SignDate = DateTime.Now.AddMinutes(3);
    appearance.Image = null;
    appearance.Acro6Layers = true;
    //appearance.SetVisibleSignature(new iTextSharp.text.Rectangle(540, 290, 430, 320), 1, null);

    string Page_Attrb = "1(540, 290, 430, 320);2(540, 290, 430, 320)"; //In_Page_Attrb;

    String[] Pageattr = Page_Attrb.Split(new[] { ";" }, StringSplitOptions.RemoveEmptyEntries);


    String[] Pageattr1 = Pageattr[0].Split(new[] { "(", ")" }, StringSplitOptions.RemoveEmptyEntries);

    int PageNo = int.Parse(Pageattr1[0]);//1

    float lx = 0, ly = 0, hx = 0, hy = 0; string[] Attr = Pageattr1[1].Split(',');
    if (Attr.Length > 3)
    {
    lx = float.Parse(Attr[0]);
    ly = float.Parse(Attr[1]);
    hx = float.Parse(Attr[2]);
    hy = float.Parse(Attr[3]);
    }

    int csize = 8192;

    PdfContentByte canvas = stamper.GetOverContent(1);

    BaseFont bfTimes = BaseFont.CreateFont(BaseFont.COURIER_BOLD, BaseFont.WINANSI, BaseFont.EMBEDDED);
    iTextSharp.text.Font f = new iTextSharp.text.Font(bfTimes, iTextSharp.text.Font.BOLD, 15);
    canvas.SetFontAndSize(bfTimes, 6);

    canvas.SetTextRenderingMode(PdfContentByte.TEXT_RENDER_MODE_FILL_STROKE);
    for (int page = 0; page <= 1; page++)
    {
    String[] Pageattr2 = Pageattr[page].Split(new[] { "(", ")" }, StringSplitOptions.RemoveEmptyEntries);

    int PageNo1 = int.Parse(Pageattr2[0]);
    float lx1 = 0, ly1 = 0, hx1 = 0, hy1 = 0;

    string[] Attr1 = Pageattr2[1].Split(',');
    if (Attr1.Length > 3)
    {
    lx1 = float.Parse(Attr1[0]);
    ly1 = float.Parse(Attr1[1]);
    hx1 = float.Parse(Attr1[2]);
    hy1 = float.Parse(Attr1[3]);
    }
    iTextSharp.text.Rectangle rect = new iTextSharp.text.Rectangle(lx1, ly1, hx1, hy1);
    PdfAnnotation annotation = PdfAnnotation.CreateFreeText(stamper.Writer, rect, appearance.Layer2Text, canvas);
    PdfAppearance tp = PdfAppearance.CreateAppearance(stamper.Writer, 444, 555);
    annotation.Flags = PdfAnnotation.FLAGS_READONLY | PdfAnnotation.FLAGS_LOCKED | PdfAnnotation.FLAGS_PRINT;

    PdfDate pdfdate = new PdfDate();
    annotation.Title = "dsds";
    annotation.Border = new PdfBorderArray(0, 0, 0, new PdfDashPattern());

    annotation.Put(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED);

    stamper.AddAnnotation(annotation, PageNo1);
    }


    Dictionary<PdfName, int> exclusionSizes = new Dictionary<PdfName, int>();
    exclusionSizes[PdfName.CONTENTS] = csize * 2 + 2;

    appearance.CryptoDictionary = (PdfDictionary)new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED)
    {
    Reason = appearance.Reason,
    Location = appearance.Location,
    Contact = appearance.Contact,
    Date = new PdfDate(appearance.SignDate)
    };
    appearance.PreClose(exclusionSizes);

    Stream s = appearance.GetRangeStream();
    //byte[] by = GetStreamAsByteArray(s);
    //string hashdocument = GenerateFilehash256Hex(by);

    string hashdocument = genaratePDFHash(s);
    string eSignReq = Esigndoc(In_OTP, In_Aadhaar_No, hashdocument);
    string res = postXMLData(ConfigurationManager.AppSettings["eSignURL"].ToString(), eSignReq);
    //Fetch the Esign XML response..
    XmlDocument xmlDocument = new XmlDocument();
    xmlDocument.LoadXml(res);
    XmlNode xmlNode = xmlDocument.SelectSingleNode("EsignResp");
    if (xmlNode.Attributes["errCode"] != null && xmlNode.Attributes["errCode"].Value != "NA")
    {

    }
    else
    {
    byte[] numArray3 = this.SignDocument(res);
    byte[] bytes1 = new byte[csize];
    Array.Copy((Array)numArray3, 0, (Array)bytes1, 0, numArray3.Length);
    PdfDictionary update = new PdfDictionary();
    update.Put(PdfName.CONTENTS, (PdfObject)new PdfString(bytes1).SetHexWriting(true));
    appearance.Close(update);
    //progressBar1.Value = 100;
    // MessageBox.Show("eSign Operation completed successfully.");
    //fileStream1.Close();
    //fileStream.Close();
    //lblMsg.Text = "File Signed Successfully";


    //For Multiple eSign Doc Start Here ...............
    //if (Pageattr.Length > 1)
    //{
    // for (int k = 1; k <= Pageattr.Length - 1; k++)
    // {
    // String[] Pageattr1 = Pageattr[k].Split(new[] { "(", ")" }, StringSplitOptions.RemoveEmptyEntries);

    // PageNo = int.Parse(Pageattr1[0]);
    // lx = 0; ly = 0; hx = 0; hy = 0;

    // string[] Attr = Pageattr1[1].Split(',');
    // if (Attr.Length > 3)
    // lx = float.Parse(Attr[0]);
    // ly = float.Parse(Attr[1]);
    // hx = float.Parse(Attr[2]);
    // hy = float.Parse(Attr[3]);
    // }
    // New_File_Name = PdfeSign(New_File_Name, PageNo, res, lx, ly, hx, hy, strLayer2Text);
    // }
    //}
    //For Multiple eSign Doc End Here ...............

    }


    }
    catch (Exception ex)
    {
    stamper.Close();
    pdfReader.Close();
    }
    finally
    {
    stamper.Close();
    pdfReader.Close();
    }