Dart

JWE using "dir" Direct use of Shared Symmetric Key

See more JSON Web Encryption (JWE) Examples

Demonstrates how to create a JWE using the "dir" alg -- which is to directly use a shared symmetric key.

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', 'dir');
  jweProtHdr.appendString('enc', 'A128GCM');

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

  // The JWE is to use 128-bit AES GCM encryption as specified by the "enc" parameter.
  // Given that the "alg" = "dir", we are to directly specify the AES GCM key.
  // (It is assumed that the decrypting side also has knowledge of the direct key to be used..)

  // Our key will be these 16 hex bytes: 000102030405060708090A0B0C0D0E0F

  // The SetWrappingKey method is also used for "dir" direct keys.
  // However, if there are multiple recipients, they must all share the same CEK (Content Encryption Key),
  // which is specified by calling SetWrappingKey with an index of 0.

  final recipientIndex = 0;
  jwe.setWrappingKey(recipientIndex, '000102030405060708090A0B0C0D0E0F', 'hex');

  // 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;
  }

  jwe2.setWrappingKey(0, '000102030405060708090A0B0C0D0E0F', 'hex');

  // 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:
  // eyJhbGciOiJkaXIiLCJlbmMiOiJBMTI4R0NNIn0..20HX5Huc7f1nQC4pBUtiCQ.axFZIxtZy5j0ifJQUzGXLKIpsBuxJA.eBrOC-NrsreN6JeGuOPk1g
  // original text: 
  // Live long and prosper.
}