915401 Added sample project.

Digital Signature/TimestampingPDFwithExternalSigning/.NET/TimestampingPDFwithExternalSigning.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.10.35122.118
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "TimestampingPDFwithExternalSigning", "TimestampingPDFwithExternalSigning\TimestampingPDFwithExternalSigning.csproj", "{076C52CD-6650-441A-848E-DF80295CDFD5}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{076C52CD-6650-441A-848E-DF80295CDFD5}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{076C52CD-6650-441A-848E-DF80295CDFD5}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{076C52CD-6650-441A-848E-DF80295CDFD5}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{076C52CD-6650-441A-848E-DF80295CDFD5}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {EEFF8B02-E955-4312-AB2F-1774A09D5BD9}
+	EndGlobalSection
+EndGlobal

Digital Signature/TimestampingPDFwithExternalSigning/.NET/TimestampingPDFwithExternalSigning/Program.cs

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+using Syncfusion.Pdf.Parsing;
+using Syncfusion.Pdf.Security;
+using Syncfusion.Drawing;
+using System.Security.Cryptography.X509Certificates;
+using System.Security.Cryptography;
+using Org.BouncyCastle.Tsp;
+using System.Net;
+using System.Text;
+using Org.BouncyCastle.Math;
+
+namespace Externally_sign_the_PDF_document
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            //Get the stream from the document
+            FileStream documentStream = new FileStream(Path.GetFullPath(@"Data/Barcode.pdf"), FileMode.Open, FileAccess.Read);
+            //Load the existing PDF document
+            PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);
+
+            //Creates a digital signature.
+            PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");
+            //Sets the signature information.
+            signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
+            signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
+            signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;
+
+            //Create an external signer.
+            IPdfExternalSigner externalSignature = new ExternalSigner("SHA1");
+
+            //Add public certificates.
+            List<X509Certificate2> certificates = new List<X509Certificate2>();
+            certificates.Add(new X509Certificate2(new X509Certificate2(Path.GetFullPath(@"Data/PDF.pfx"), "password123")));
+            signature.AddExternalSigner(externalSignature, certificates, null);
+
+            //Create file stream.
+            using (FileStream outputFileStream = new FileStream(Path.GetFullPath(@"Output/Output.pdf"), FileMode.Create, FileAccess.ReadWrite))
+            {
+                //Save the PDF document to file stream.
+                loadedDocument.Save(outputFileStream);
+            }
+            //Close the document.
+            loadedDocument.Close(true);
+        }
+        //Create the external signer class and sign the document hash.
+        class ExternalSigner : IPdfExternalSigner
+        {
+            private string _hashAlgorithm;
+            public string HashAlgorithm
+            {
+                get { return _hashAlgorithm; }
+            }
+            public ExternalSigner(string hashAlgorithm)
+            {
+                _hashAlgorithm = hashAlgorithm;
+            }
+            public byte[] Sign(byte[] message, out byte[] timeStampResponse)
+            {
+                byte[] signedBytes = null;
+                X509Certificate2 digitalID = new X509Certificate2(new X509Certificate2(Path.GetFullPath(@"Data/PDF.pfx"), "password123"));
+                if (digitalID.PrivateKey is System.Security.Cryptography.RSACryptoServiceProvider)
+                {
+                    System.Security.Cryptography.RSACryptoServiceProvider rsa = (System.Security.Cryptography.RSACryptoServiceProvider)digitalID.PrivateKey;
+                    signedBytes = rsa.SignData(message, HashAlgorithm);
+                }
+                else if (digitalID.PrivateKey is RSACng)
+                {
+                    RSACng rsa = (RSACng)digitalID.PrivateKey;
+                    signedBytes = rsa.SignData(message, System.Security.Cryptography.HashAlgorithmName.SHA1, RSASignaturePadding.Pkcs1);
+                }
+                timeStampResponse = GetRFC3161TimeStampToken(signedBytes);
+
+                return signedBytes;
+            }
+            public byte[] GetRFC3161TimeStampToken(byte[] bytes)
+            {
+                SHA1 sha1 = SHA1CryptoServiceProvider.Create();
+                byte[] hash = sha1.ComputeHash(bytes);
+                TimeStampRequestGenerator reqGen = new TimeStampRequestGenerator();
+                reqGen.SetCertReq(true);
+                TimeStampRequest tsReq = reqGen.Generate(TspAlgorithms.Sha1, hash, BigInteger.ValueOf(100));
+                byte[] tsData = tsReq.GetEncoded();
+                HttpWebRequest req = (HttpWebRequest)WebRequest.Create("https://rfc3161.ai.moda"); // Update your timestamp Uri here
+                req.Method = "POST";
+                req.ContentType = "application/timestamp-query";
+                req.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(Encoding.ASCII.GetBytes("9024:yourPass")));
+                req.ContentLength = tsData.Length;
+                Stream reqStream = req.GetRequestStream();
+                reqStream.Write(tsData, 0, tsData.Length);
+                reqStream.Close();
+                HttpWebResponse res = (HttpWebResponse)req.GetResponse();
+                if (res != null)
+                {
+                    Stream resStream = new BufferedStream(res.GetResponseStream());
+                    TimeStampResponse tsRes = new TimeStampResponse(resStream);
+                    return tsRes.TimeStampToken.GetEncoded();
+                }
+                return null;
+            }
+        }
+    }
+}

Digital Signature/TimestampingPDFwithExternalSigning/.NET/TimestampingPDFwithExternalSigning/TimestampingPDFwithExternalSigning.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="BouncyCastle" Version="*" />
+    <PackageReference Include="Syncfusion.Pdf.Net.Core" Version="*" />
+  </ItemGroup>
+
+</Project>