Dart Requires Chilkat v9.5.0.85+

Sign PDF with Timestamp from TSA (Timestamp Server Authority)

See more PDF Signatures Examples

This example demonstrates how to a sign a PDF that is both long-term validation (LTV) enabled and includes a validating timestamp from a TSA (Timestamp Server Authority). Dart

import 'package:chilkat/chilkat.dart';

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

  final pdf = CkPdf();

  // Load a PDF to be signed.
  // The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
  try {
    pdf.loadFile('qa_data/pdf/hello.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Options for signing are specified in JSON.
  final json = CkJsonObject();

  // In most cases, the signingCertificateV2 and signingTime attributes are required.
  json.updateInt('signingCertificateV2', 1);
  json.updateInt('signingTime', 1);

  // Tell Chilkat to create an LTV-enabled (long term validation) signature.
  // See PDF Long-Term Validation (LTV) Signature Example for more detailed comments about "ltvOcsp".
  json.updateBool('ltvOcsp', true);

  // Tell Chilkat to request a timestamp from a TSA server and include the timestamp token (1.2.840.113549.1.9.16.2.14)
  // in the CMS signature's authentication attributes
  json.updateBool('timestampToken.enabled', true);

  // In this example, we'll use a free TSA server (timestamp.digicert.com), but you may want to use your own timestamp authority server.
  json.updateString('timestampToken.tsaUrl', 'http://timestamp.digicert.com');

  // If the timestamp server requires a username/password, do the following.  Otherwise omit the following few lines of code.
  json.updateString('timestampToken.tsaUsername', 'the_tsa_username');
  json.updateString('timestampToken.tsaPassword', 'the_tsa_password');

  // When requesting the timestamp token, ask the server to include its certificate in the timestamp token response.
  // This allows for the timestamp server's certificate to be included in the LTV validation (i.e. if the timestamp server
  // has an OCSP URL, then Chilkat will also do the OCSP request for the timestamp server's certificate.)
  json.updateBool('timestampToken.requestTsaCert', true);

  // Define the appearance of the signature.
  json.updateInt('page', 1);
  json.updateString('appearance.y', 'top');
  json.updateString('appearance.x', 'left');
  json.updateString('appearance.fontScale', '10.0');
  json.updateString('appearance.text[0]', 'Digitally signed by: cert_cn');
  json.updateString('appearance.text[1]', 'current_dt');
  json.updateString('appearance.text[2]', 'This is an LTV-enabled signature with a TSA timestamp.');

  // Load the signing certificate. (Use your own certificate.)
  final cert = CkCert();
  try {
    cert.loadPfxFile('qa_data/pfx/myPdfSigningCert.pfx', 'pfxPassword');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Tell the pdf object to use the certificate for signing.
  try {
    pdf.setSigningCert(cert);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    pdf.signPdf(json, 'qa_output/hello_ltv_signed_with_timestamp.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('The PDF has been successfully cryptographically signed with TSA timestamp and long-term validation.');

  // If you open the Signature Panel in Adobe Acrobat, it will indicate that the signature is LTV enabled
  // and contains an embedded timestamp:
  // (image:https://example-code.com/images/ltv_signature_with_timestamp.jpg/endImage)
}