Dart

JWE with Binary Data

See more JSON Web Encryption (JWE) Examples

Demonstrates how to create a JWE that contains a binary payload (such as a JPG image).

Note: This example requires Chilkat v9.5.0.66 or greater.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  var success = false;

  // This requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // Note: This example requires Chilkat v9.5.0.66 or greater.

  // Load a JPG file that will be the JWE payload.
  final jpgBytes = CkBinData();
  success = true;
  try {
    jpgBytes.loadFile('qa_data/jpg/starfish.jpg');
  } on ChilkatException {
    success = false;
  }
  // Make sure your app checks the success/failure of the call to LoadFile..
  print('Original JPG size = ${jpgBytes.numBytes}');

  final jwe = CkJwe();

  final jweProtHdr = CkJsonObject();
  jweProtHdr.appendString('alg', 'A128KW');
  jweProtHdr.appendString('enc', 'A128CBC-HS256');
  jwe.setProtectedHeader(jweProtHdr);

  final aesWrappingKey = 'GawgguFyGrWKav7AX4VKUg';
  jwe.setWrappingKey(0, aesWrappingKey, 'base64url');

  // Encrypt and return the JWE in sbJwe:
  final sbJwe = CkStringBuilder();
  try {
    jwe.encryptBd(jpgBytes, sbJwe);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Show the JWE:
  print(sbJwe.getAsString());
  print('size of JWE: ${sbJwe.length}');

  // ---------------------------------------------------------
  // Decrypt to get the original JPG file..

  final jwe2 = CkJwe();
  try {
    jwe2.loadJweSb(sbJwe);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Set the AES wrap key.
  jwe2.setWrappingKey(0, aesWrappingKey, 'base64url');

  // Decrypt.
  final jpgOriginal = CkBinData();
  try {
    jwe2.decryptBd(0, jpgOriginal);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Decrypted JPG size = ${jpgOriginal.numBytes}');

  // Save the decrypted JPG to a file.
  success = true;
  try {
    jpgOriginal.writeFile('qa_output/jwe_decrypted_starfish.jpg');
  } on ChilkatException {
    success = false;
  }

  print('success = $success');

  // The output of this program, when tested, was:
  // Original JPG size = 6229
  // eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.9YFz_wteV ... 7Et3hKhpxnKEXw
  // size of JWE: 8473
  // Decrypted JPG size = 6229
  // success = True
}