Dart

JWE with DEFLATE Compression

See more JSON Web Encryption (JWE) Examples

Demonstrates how to DEFLATE ("zip") compress the JWE payload prior to encryption.

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.

  // Create some plaintext to be encrypted.
  // This example will demonstrate with and without DEFLATE (zip) compression.
  final sbPlainText = CkStringBuilder();
  final bCrLf = true;
  final line = 'Live long and prosper.';
  sbPlainText.appendLine(line, bCrLf);
  sbPlainText.appendLine(line, bCrLf);
  sbPlainText.appendLine(line, bCrLf);
  sbPlainText.appendLine(line, bCrLf);

  // The text to be encrypted:
  print(sbPlainText.getAsString());

  final jwe = CkJwe();

  // Build the JWE Protected Header: {"alg":"A128KW","enc":"A128CBC-HS256","zip":"DEF"}
  // The "zip":"DEF" parameter indicates that the plaintext payload should
  // be compressed prior to encryption.
  final jweProtHdr = CkJsonObject();
  jweProtHdr.appendString('alg', 'A128KW');
  jweProtHdr.appendString('enc', 'A128CBC-HS256');
  jweProtHdr.appendString('zip', 'DEF');
  jwe.setProtectedHeader(jweProtHdr);

  // Set the AES key wrap key:
  final aesWrappingKey = 'GawgguFyGrWKav7AX4VKUg';
  jwe.setWrappingKey(0, aesWrappingKey, 'base64url');

  // Encrypt and return the JWE in sbJweCompressed:
  final sbJweCompressed = CkStringBuilder();
  try {
    jwe.encryptSb(sbPlainText, 'utf-8', sbJweCompressed);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  // Now create a JWE without compression.
  jweProtHdr.delete('zip');
  // Make sure to update the shared protected header:
  jwe.setProtectedHeader(jweProtHdr);

  final sbJweUncompressed = CkStringBuilder();
  try {
    jwe.encryptSb(sbPlainText, 'utf-8', sbJweUncompressed);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  // Decrypting is the same whether compression is used or not.
  // The "zip" header in the JWE indicates that the payload should be 
  // automatically decompressed (inflated) after decrypting.
  final jwe2 = CkJwe();
  try {
    jwe2.loadJweSb(sbJweCompressed);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  // Decrypt (also automatically decompresses).
  final sbOriginalText = CkStringBuilder();
  try {
    jwe2.decryptSb(0, 'utf-8', sbOriginalText);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('original text from compressed JWE: ');
  print(sbOriginalText.getAsString());

  // -----------------------------------------------------------
  // Do the same with the uncompressed JWE

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

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

  // Decrypt.
  sbOriginalText.clear();
  try {
    jwe2.decryptSb(0, 'utf-8', sbOriginalText);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('original text from uncompressed JWE: ');
  print(sbOriginalText.getAsString());

  // ------------------------------------------------
  // The output of this example is:
  // (Note: Your output data will be different because the content encryption key is randomly generated.)

  // eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2IiwiemlwIjoiREVGIn0.xuW-pEAIdEUFnk10m8ocursvktO8Of9ByCCAt6LgKkkOtCWCUn1kQw.zpGj-9WVni3cQxyOuZbcGA.0hzP1myua3oYpUHwCIY_3edBUREbUpLaX6wYuJduOdI.Ppc6aEO3y3B8BJ1FKMPjlA
  // size of compressed JWE: 212
  // eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.N4KeyC7nnSFkieJOyE24_zKeuV_m7v5UKoJb1TgV4Yc_r2RzUPNvyA.6AEdyXSCKx-iMmUJyypSLg.QpixfyrwhGpmwUDp623viik4smPav7vwPLiC2r-V-jwnSfEH3mxWu6DbrIz3mixaqATwynmEBzVPxvS9jTXpSAGCnniib4_0WoPl3r_wF5tlsKOEe--jpNso-DKd1Tp8jJxj3JkFWt3IRnUUKGj17g.sBfDwFc5fzpaI-UW8-SW4g
  // size of uncompressed JWE: 303
  // original text from compressed JWE: 
  // Live long and prosper.
  // Live long and prosper.
  // Live long and prosper.
  // Live long and prosper.
  // 
  // original text from uncompressed JWE: 
  // Live long and prosper.
  // Live long and prosper.
  // Live long and prosper.
  // Live long and prosper.
  // 
}