Dart

Create CMS Signed File (PDF) with Multiple Signing Certificates

See more Digital Signatures Examples

Demonstrates how to sign a file by adding multiple signatures (multiple certificates). This example signs a PDF file to produce an output file that is a CMS signature wrapping the original PDF. (Note: This is different than modifying a PDF by injecting a signature into the PDF file format.)

Note: This example requires Chilkat v9.5.0.83 or greater.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example assumes the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final crypt = CkCrypt2();

  // ------------ This example requires Chilkat v9.5.0.83 or greater.

  final cert1 = CkCert();
  try {
    cert1.loadPfxFile('qa_data/pfx/cert_test123.pfx', 'test123');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final cert2 = CkCert();
  try {
    cert2.loadPfxFile('qa_data/pfx/test_secret.pfx', 'secret');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // ------------ This example requires Chilkat v9.5.0.83 or greater.

  // Tell the crypt component to use both certificates for signing. 
  // When we create the signature, it will be signed by both certificates.
  try {
    crypt.addSigningCert(cert1);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    crypt.addSigningCert(cert2);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // The CadesEnabled property applies to all methods that create PKCS7 signatures. 
  // To create a CAdES-BES signature, set this property equal to true. 
  crypt.cadesEnabled = true;

  crypt.hashAlgorithm = 'sha256';

  // We can sign any type of file, creating a .p7s as output.
  // The .p7s contains the signature and also embeds the data of the file that is signed.
  final inFile = 'qa_data/pdf/sample.pdf';
  final p7sFile = 'qa_output/sample.pdf.p7s';

  // Create the CAdES-BES attached signature, which contains the original data.
  // Note: Chilkat's function naming is not accurate.  CreateP7M creates a PKCS7 signature where the signed file
  // is contained within the signature.  CreateP7S creates a detached PKCS7 signature where the signed file
  // is NOT contained within the signature.  We want the data to be contained in the signature, therefore
  // we call CreateP7M even though we are naming our output file .p7s.
  try {
    crypt.createP7M(inFile, p7sFile);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Verify the .p7s file and extract the original file from the .p7s. 
  final extractedToFilePath = 'qa_output/sample.pdf';
  try {
    crypt.verifyP7M(p7sFile, extractedToFilePath);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Success!');
}