Dart Requires Chilkat v11.7.0+

Choose the PDF Encryption Algorithm: AES-256, AES-128 or RC4

See more PDF Protection Examples

Demonstrates the algorithmChoice option of the encrypt operation. aes-256 is the default and the one to use unless an older reader must open the file. aes-128 is for readers that predate AES-256. rc4-128 and rc4-40 are broken ciphers kept only for very old readers. Each algorithm needs a minimum PDF version, and the file header is raised to it when the PDF is saved, never lowered. A PDF saved with RC4 is written with a classic cross-reference table so that those old readers can parse it. 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.

  // The PDF used in this example is available at two_page_memo.pdf

  final json = CkJsonObject();
  final jsonOut = CkJsonObject();
  final info = CkJsonObject();

  // AES-256, the default.  Saved as PDF 1.7 with Adobe extension level 8.
  final pdf1 = CkPdf();
  try {
    pdf1.loadFile('qa_data/pdf/two_page_memo.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  pdf1.userPassword = 'user-secret';
  pdf1.ownerPassword = 'owner-secret';
  json.updateString('algorithmChoice', 'aes-256');
  try {
    pdf1.protection('encrypt', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('aes-256 will be saved as PDF ${jsonOut.stringOf('pending.pdfVersion')}, Adobe extension level ${jsonOut.intOf('pending.adobeExtensionLevel')}');
  try {
    pdf1.writeFile('qa_output/memo_aes256.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    pdf1.preLoadCheck('qa_output/memo_aes256.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('  saved file: ${info.stringOf('algorithm')}, PDF ${info.stringOf('pdfVersion')}');

  // AES-128, for readers that predate AES-256.  Saved as PDF 1.6.
  final pdf2 = CkPdf();
  try {
    pdf2.loadFile('qa_data/pdf/two_page_memo.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  pdf2.userPassword = 'user-secret';
  pdf2.ownerPassword = 'owner-secret';
  json.updateString('algorithmChoice', 'aes-128');
  try {
    pdf2.protection('encrypt', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('aes-128 will be saved as PDF ${jsonOut.stringOf('pending.pdfVersion')}');
  try {
    pdf2.writeFile('qa_output/memo_aes128.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    pdf2.preLoadCheck('qa_output/memo_aes128.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('  saved file: ${info.stringOf('algorithm')}, PDF ${info.stringOf('pdfVersion')}');

  // RC4-128, a broken cipher, only for readers too old for AES.  Saved as PDF 1.4.
  final pdf3 = CkPdf();
  try {
    pdf3.loadFile('qa_data/pdf/two_page_memo.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  pdf3.userPassword = 'user-secret';
  pdf3.ownerPassword = 'owner-secret';
  json.updateString('algorithmChoice', 'rc4-128');
  try {
    pdf3.protection('encrypt', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('rc4-128 will be saved as PDF ${jsonOut.stringOf('pending.pdfVersion')}');
  try {
    pdf3.writeFile('qa_output/memo_rc4_128.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    pdf3.preLoadCheck('qa_output/memo_rc4_128.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('  saved file: ${info.stringOf('algorithm')}, PDF ${info.stringOf('pdfVersion')}');

  // Sample output:

  // aes-256 will be saved as PDF 1.7, Adobe extension level 8
  //   saved file: aes-256, PDF 1.7
  // aes-128 will be saved as PDF 1.6
  //   saved file: aes-128, PDF 1.6
  // rc4-128 will be saved as PDF 1.4
  //   saved file: rc4-128, PDF 1.4
}