Dart

JWE using PBES2 Key Wrapping

See more JSON Web Encryption (JWE) Examples

Demonstrates how to create and decrypt a JWE that using PBES2 key wrapping.

This example demonstrates PBES2 with HMAC SHA-256 and A128KW wrapping. It is also possible to do the following by simply changing the "alg" parameter:

• PBES2 with HMAC SHA-384 and A192KW wrapping
• PBES2 with HMAC SHA-512 and A256KW wrapping

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

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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.

  final plaintext = 'Live long and prosper.';

  final jwe = CkJwe();

  // First build the JWE Protected Header..
  final jweProtHdr = CkJsonObject();
  jweProtHdr.appendString('alg', 'PBES2-HS256+A128KW');
  jweProtHdr.appendString('enc', 'A128GCM');

  // PBES2 requires two additional parameters:
  // 1) A random salt parameter ("p2s") containing 8 or more bytes in base64url format.
  // 2) An iteration count parameter ("p2c").  A minimum count of 1000 is recommended.
  //    The iteration count is intended to make the PBES2 computation more expensive (time consuming)
  //    to prevent brute-force attacks.
  final prng = CkPrng();
  jweProtHdr.appendString('p2s', prng.genRandom(16, 'base64url'));
  jweProtHdr.appendString('p2c', '1000');

  print('JWE Protected Header: ${jweProtHdr.emit()}');
  print('--');

  // Don't forget to actually provide the protected header to the JWE object:
  jwe.setProtectedHeader(jweProtHdr);

  // Set the PBES2 password
  final recipientIndex = 0;
  jwe.setPassword(recipientIndex, 'top secret');

  // Encrypt and return the JWE:
  final String strJwe;
  try {
    strJwe = jwe.encrypt(plaintext, 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Show the JWE we just created:
  print(strJwe);

  // Decrypt the JWE.
  final jwe2 = CkJwe();
  try {
    jwe2.loadJwe(strJwe);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Set the PBES2 password
  jwe2.setPassword(recipientIndex, 'top secret');

  // Decrypt.
  final String originalPlaintext;
  try {
    originalPlaintext = jwe2.decrypt(0, 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('original text: ');
  print(originalPlaintext);

  // Sample output:

  // JWE Protected Header: {"alg":"PBES2-HS256+A128KW","enc":"A128GCM","p2s":"z39rTEfRy1T1Yn_D1mZRlg","p2c":"1000"}
  // --
  // eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJlbmMiOiJBMTI4R0NNIiwicDJzIjoiejM5clRFZlJ5MVQxWW5fRDFtWlJsZyIsInAyYyI6IjEwMDAifQ.koYt6PrFmYwcwdcT7ZcvXHA1d-Xez5h4.luGlbvEnZp-7IsBOj42Yhw.YMTcfLf8Qe4zazozGV2OAu3cUdQ8Kg.rWub47ESWkc6IqZJTvSTmg
  // original text: 
  // Live long and prosper.
}