Dart

JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256

See more JSON Web Encryption (JWE) Examples

This example duplicates the example A.3 in RFC 7516 for JSON Web Encryption (JWE).

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

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

  // The example A.3 in RFC 7516 uses the following 128-bit AES key,
  // specified in JWK (JSON Web Key) format:
  //      {"kty":"oct",
  //       "k":"GawgguFyGrWKav7AX4VKUg"
  //      }
  // This is just a way of saying: The key type ("kty") is 
  // a bunch of octets ("k") in base64url encoding.
  // We can simply set the AES wrapping key like this:
  final aesWrappingKey = 'GawgguFyGrWKav7AX4VKUg';
  jwe.setWrappingKey(0, aesWrappingKey, 'base64url');

  // 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 that was just produced.
  // 1) Load the JWE.
  // 2) Set the AES wrapping key.
  // 3) Decrypt.
  final jwe2 = CkJwe();
  try {
    jwe2.loadJwe(strJwe);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

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

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

  // ---------------------------------------------------------------------------------
  // It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.3.7
  // because it was produced using the same AES Wrap key.

  final sbJwe = CkStringBuilder();
  sbJwe.append('eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.');
  sbJwe.append('6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.');
  sbJwe.append('AxY8DCtDaGlsbGljb3RoZQ.');
  sbJwe.append('KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.');
  sbJwe.append('U0m_YmjN04DJvceFICbCVQ');

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

  jwe2.setWrappingKey(0, aesWrappingKey, 'base64url');

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

  print(originalPlaintext);
}