在C#中使用Itextsharp为PDF添加数字签名

using iTextSharp.text.pdf;
using iTextSharp.text.pdf.security;

Imports iTextSharp.text.pdf
Imports iTextSharp.text.pdf.security

using IronPdf;

Imports IronPdf

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

Imports System
Imports System.IO
Imports System.Linq
Imports iTextSharp.text.pdf
Imports iTextSharp.text.pdf.security
Imports Org.BouncyCastle.Crypto
Imports Org.BouncyCastle.Pkcs

// Path to the unsigned PDF you want to sign
string filename = "example.pdf";

// Load the existing PDF into a reader
PdfReader pdfReader = new PdfReader(filename);

string reason = "Digital Signature Reason";
string location = "Digital Signature Location";

' Path to the unsigned PDF you want to sign
Dim filename As String = "example.pdf"

' Load the existing PDF into a reader
Dim pdfReader As New PdfReader(filename)

Dim reason As String = "Digital Signature Reason"
Dim location As String = "Digital Signature Location"

// Path to your .pfx certificate file (must contain private key)
string pfxFilePath = "certificate-file.pfx";

// Password for the certificate (make sure to protect this securely!)
string pfxPassword = "Password";

' Path to your .pfx certificate file (must contain private key)
Dim pfxFilePath As String = "certificate-file.pfx"

' Password for the certificate (make sure to protect this securely!)
Dim pfxPassword As String = "Password"

// Initialize a new PKCS#12 key store (used for handling the PFX certificate)
Pkcs12StoreBuilder pkcs12StoreBuilder = new Pkcs12StoreBuilder();
Pkcs12Store pfxKeyStore = pkcs12StoreBuilder.Build();

// Load the certificate and private key from the PFX file
using (FileStream pfxStream = new FileStream(pfxFilePath, FileMode.Open, FileAccess.Read))
{
    // Load into the key store using the provided password
    pfxKeyStore.Load(pfxStream, pfxPassword.ToCharArray());
}

' Initialize a new PKCS#12 key store (used for handling the PFX certificate)
Dim pkcs12StoreBuilder As New Pkcs12StoreBuilder()
Dim pfxKeyStore As Pkcs12Store = pkcs12StoreBuilder.Build()

' Load the certificate and private key from the PFX file
Using pfxStream As New FileStream(pfxFilePath, FileMode.Open, FileAccess.Read)
	' Load into the key store using the provided password
	pfxKeyStore.Load(pfxStream, pfxPassword.ToCharArray())
End Using

// Create a PdfStamper that enables signing and appends the signature to the document
PdfStamper pdfStamper = PdfStamper.CreateSignature(
    pdfReader,
    new FileStream("MyPDF_Signed.pdf", FileMode.Create), // Output path
    '\0',                                                // PDF version (unchanged)
    null,                                                // Temp file path (optional)
    true                                                 // Append mode (preserves original content)
);

Imports Microsoft.VisualBasic

' Create a PdfStamper that enables signing and appends the signature to the document
Dim pdfStamper As PdfStamper = PdfStamper.CreateSignature(pdfReader, New FileStream("MyPDF_Signed.pdf", FileMode.Create), ControlChars.NullChar, Nothing, True)

// Access the signature appearance settings
PdfSignatureAppearance signatureAppearance = pdfStamper.SignatureAppearance;

// Add optional metadata (shows up in PDF signature details)
signatureAppearance.Reason = reason;
signatureAppearance.Location = location;

// Position the visible signature on the page (x, y, width, height in points)
float x = 360;
float y = 130;
signatureAppearance.Acro6Layers = false;              // Use compact signature appearance
signatureAppearance.Layer4Text = PdfSignatureAppearance.QuestionMark; // Custom label text
signatureAppearance.SetVisibleSignature(
    new iTextSharp.text.Rectangle(x, y, x + 150, y + 50), // Rectangle position
    1,                                                    // Page number
    "signature"                                           // Field name
);

' Access the signature appearance settings
Dim signatureAppearance As PdfSignatureAppearance = pdfStamper.SignatureAppearance

' Add optional metadata (shows up in PDF signature details)
signatureAppearance.Reason = reason
signatureAppearance.Location = location

' Position the visible signature on the page (x, y, width, height in points)
Dim x As Single = 360
Dim y As Single = 130
signatureAppearance.Acro6Layers = False ' Use compact signature appearance
signatureAppearance.Layer4Text = PdfSignatureAppearance.QuestionMark ' Custom label text
signatureAppearance.SetVisibleSignature(New iTextSharp.text.Rectangle(x, y, x + 150, y + 50), 1, "signature")

// Find the first alias in the PFX that has a private key entry
string alias = pfxKeyStore.Aliases.Cast<string>().FirstOrDefault(
    entryAlias => pfxKeyStore.IsKeyEntry(entryAlias)
);

// Ensure a valid alias (certificate) was found
if (alias != null)
{
    // Retrieve the private key for signing
    ICipherParameters privateKey = pfxKeyStore.GetKey(alias).Key;

    // Create a signer using SHA-256 and the private key
    IExternalSignature pks = new PrivateKeySignature(privateKey, DigestAlgorithms.SHA256);

    // Perform the digital signing operation using CMS format
    MakeSignature.SignDetached(
        signatureAppearance,     // Signature appearance
        pks,                     // External signature handler
        new Org.BouncyCastle.X509.X509Certificate[] {
            pfxKeyStore.GetCertificate(alias).Certificate
        },                       // Certificate chain (basic single-cert example)
        null, null, null,        // Optional CRL, OCSP, TSA
        0,                       // Estimated size for the signature (0 = auto)
        CryptoStandard.CMS       // Signature standard (CMS vs CAdES)
    );
}
else
{
    Console.WriteLine("Private key not found in the PFX certificate.");
}

' Find the first alias in the PFX that has a private key entry
Dim [alias] As String = pfxKeyStore.Aliases.Cast(Of String)().FirstOrDefault(Function(entryAlias) pfxKeyStore.IsKeyEntry(entryAlias))

' Ensure a valid alias (certificate) was found
If [alias] IsNot Nothing Then
	' Retrieve the private key for signing
	Dim privateKey As ICipherParameters = pfxKeyStore.GetKey([alias]).Key

	' Create a signer using SHA-256 and the private key
	Dim pks As IExternalSignature = New PrivateKeySignature(privateKey, DigestAlgorithms.SHA256)

	' Perform the digital signing operation using CMS format
	MakeSignature.SignDetached(signatureAppearance, pks, New Org.BouncyCastle.X509.X509Certificate() { pfxKeyStore.GetCertificate([alias]).Certificate }, Nothing, Nothing, Nothing, 0, CryptoStandard.CMS)
Else
	Console.WriteLine("Private key not found in the PFX certificate.")
End If

// Close the stamper to save and finalize the signed PDF
pdfStamper.Close();

' Close the stamper to save and finalize the signed PDF
pdfStamper.Close()

using IronPdf;

var renderer = new ChromePdfRenderer();

string securityConfigForm = @"
<!DOCTYPE html>
<html>
<head>
    <meta charset='utf-8'>
    <link href='https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css' rel='stylesheet'>
    <style>
        .step-indicator { display: flex; justify-content: space-between; margin-bottom: 30px; }
        .step { flex: 1; text-align: center; position: relative; }
        .step-number { width: 40px; height: 40px; border-radius: 50%; background: #e9ecef;
            display: inline-flex; align-items: center; justify-content: center; font-weight: 700; }
        .step.completed .step-number { background: #198754; color: white; }
        .step.active .step-number { background: #0d6efd; color: white; }
        @media print { .form-section { page-break-inside: avoid; } }
    </style>
</head>
<body class='bg-light'>
    <div class='container py-4'>
        <div class='row justify-content-center'>
            <div class='col-lg-8'>
                <h2 class='text-center mb-4'>PDF Security Configuration</h2>

                <div class='step-indicator mb-4'>
                    <div class='step completed'>
                        <div class='step-number'>✓</div>
                        <div class='small mt-2'>Certificate</div>
                    </div>
                    <div class='step completed'>
                        <div class='step-number'>✓</div>
                        <div class='small mt-2'>Signature</div>
                    </div>
                    <div class='step active'>
                        <div class='step-number'>3</div>
                        <div class='small mt-2'>Encryption</div>
                    </div>
                    <div class='step'>
                        <div class='step-number'>4</div>
                        <div class='small mt-2'>Finalize</div>
                    </div>
                </div>

                <div class='card shadow-sm form-section'>
                    <div class='card-header bg-primary text-white'>
                        <h5 class='mb-0'>Step 3: Encryption & Permissions</h5>
                    </div>
                    <div class='card-body'>
                        <div class='mb-3'>
                            <label class='form-label'><strong>Encryption Level</strong></label>
                            <select class='form-select'>
                                <option>AES 128-bit</option>
                                <option selected>AES 256-bit (Recommended)</option>
                                <option>RC4 128-bit (Legacy)</option>
                            </select>
                            <small class='text-muted'>AES-256 provides enterprise-grade security</small>
                        </div>

                        <div class='mb-3'>
                            <label class='form-label'><strong>Document Permissions</strong></label>
                            <div class='form-check form-switch'>
                                <input class='form-check-input' type='checkbox' id='allowPrint' checked>
                                <label class='form-check-label' for='allowPrint'>Allow Printing</label>
                            </div>
                            <div class='form-check form-switch'>
                                <input class='form-check-input' type='checkbox' id='allowCopy'>
                                <label class='form-check-label' for='allowCopy'>Allow Content Copying</label>
                            </div>
                            <div class='form-check form-switch'>
                                <input class='form-check-input' type='checkbox' id='allowModify'>
                                <label class='form-check-label' for='allowModify'>Allow Document Modification</label>
                            </div>
                            <div class='form-check form-switch'>
                                <input class='form-check-input' type='checkbox' id='allowAnnotate' checked>
                                <label class='form-check-label' for='allowAnnotate'>Allow Annotations</label>
                            </div>
                        </div>

                        <div class='mb-3'>
                            <label class='form-label'><strong>Password Protection</strong></label>
                            <input type='password' class='form-control mb-2' placeholder='Owner Password' value='••••••••'>
                            <input type='password' class='form-control' placeholder='User Password (Optional)'>
                            <small class='text-muted'>Owner password controls document permissions</small>
                        </div>

                        <div class='alert alert-success'>
                            <strong>✓ Configuration Valid</strong><br>
                            <small>Security settings meet compliance requirements</small>
                        </div>
                    </div>
                    <div class='card-footer'>
                        <div class='d-flex justify-content-between'>
                            <button class='btn btn-outline-secondary'>← Previous</button>
                            <button class='btn btn-primary'>Continue →</button>
                        </div>
                    </div>
                </div>

                <div class='card mt-3 shadow-sm'>
                    <div class='card-body'>
                        <h6 class='text-primary'>Security Comparison</h6>
                        <div class='row g-2'>
                            <div class='col-6'>
                                <div class='text-center p-2 bg-success text-white rounded'>
                                    <strong>IronPDF</strong><br>
                                    <small>AES-256 Native</small>
                                </div>
                            </div>
                            <div class='col-6'>
                                <div class='text-center p-2 bg-warning text-dark rounded'>
                                    <strong>iTextSharp</strong><br>
                                    <small>Complex Setup</small>
                                </div>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        </div>
    </div>
</body>
</html>";

var pdf = renderer.RenderHtmlAsPdf(securityConfigForm);
pdf.SaveAs("security-configuration.pdf");

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