//// This code is part of Document Solutions for PDF .NET demos.// Copyright (c) MESCIUS inc. All rights reserved.//using System;using System.IO;using System.Drawing;using GrapeCity.Documents.Pdf;using GrapeCity.Documents.Pdf.Security;
namespace DsPdfWeb.Demos{    // This sample demonstrates how to create an encrypted PDF    // using the Standard Security Handler Revision 6.    //     // Standard Security Handler Revision 6 was added in PDF 2.0.    // It uses AES 256 encryption, same as the Standard Security Handler Revision 5    // described in "Adobe Supplement to the ISO 32000 BaseVersion: 1.7 ExtensionLevel: 3",    // but a new more complex algorithm is used to generate an encryption key.    //    // See SecurityHandlers for examples of using other security handlers.    public class SecurityHandlerRev6    {        public int CreatePDF(Stream stream)        {            // Sample passwords:            const string ownerPassword = "I'm the owner";            const string userPassword = "I'm a user";
            // Step 1: Generate a document with some security attributes:            var doc0 = new GcPdfDocument();            var rc0 = Common.Util.AddNote(                "Demonstrating the use of the Standard Security Handler Revision 6.",                doc0.NewPage());
            // Create a Rev6 security handler and set security properties:            var ssh6 = new StandardSecurityHandlerRev6()            {                OwnerPassword = ownerPassword,                UserPassword = userPassword,                CopyContent = false,                PrintingPermissions = PrintingPermissions.Disabled,                EncryptStrings = true,            };
            // Assign the handler we created to the document so that it is used when saving the PDF:            doc0.Security.EncryptHandler = ssh6;
            // Save the PDF in a temp file. It will be loaded and examined in the next step:            var fn = Path.GetTempFileName();            doc0.Save(fn);
            // Step 2: Load the generated PDF and examine its security attributes:            var doc = new GcPdfDocument();            using (var fs = File.OpenRead(fn))            {                // User password is needed to load the document:                doc.Load(fs, userPassword);
                // At this point we can examine doc.Security.DecryptHandler if it exists,                // but there is NO Security.EncryptHandler:                if (doc.Security.EncryptHandler != null)                    throw new Exception("This should not happen.");
                var dh = doc.Security.DecryptHandler;                if (dh is StandardSecurityHandlerRev6 dh_ssh6)                {                    // Print out some of the permissions in the loaded PDF that was generated in Step 1:                    var txt = $"Some of the security attributes found in the PDF " +                        $"that was generated using StandardSecurityHandlerRev6:\n" +                        $"- EncryptionAlgorithm: {dh_ssh6.EncryptionAlgorithm}\n" +                        $"- EncryptionKeyLength: {dh_ssh6.EncryptionKeyLength}\n" +                        $"- CopyContent: {dh_ssh6.CopyContent}\n" +                        $"- PrintingPermissions: {dh_ssh6.PrintingPermissions}\n" +                        $"- EncryptStrings: {dh_ssh6.EncryptStrings}\n" +                        $"";
                    Common.Util.AddNote(                        txt,                        doc.Pages[0],                        new RectangleF(72, rc0.Bottom + 36, 72 * 6, 72 * 2));
                    // This won't work, sorry:                    var noway = dh_ssh6.OwnerPassword;                    if (noway != null)                        throw new Exception("This should not happen.");                }
                // Save the new PDF. Please note that because we did not set the Security.EncryptHandler                // on this PDF, this document (unlike the one that was generated in Step 1) has no security:                doc.Save(stream);            }            // Clean up the temp file:            File.Delete(fn);            // Done:            return doc.Pages.Count;        }    }}