Dart

JWE Using Flattened JWE JSON Serialization

See more JSON Web Encryption (JWE) Examples

This example duplicates the example A.5 in RFC 7516 for JSON Web Encryption (JWE).

This example demonstrates using the flattened JWE JSON Serialization syntax. This example demonstrates the capability for encrypting the plaintext to a single recipient in a flattened JSON structure.

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

  // We have a single recipient that uses AES Key Wrap to encrypt the CEK.
  // 
  //      {"alg":"A128KW","kid":"7"}

  final jweRecipientHdr = CkJsonObject();
  jweRecipientHdr.appendString('alg', 'A128KW');
  jweRecipientHdr.appendString('kid', '7');
  var recipientIndex = 0;
  jwe.setRecipientHeader(recipientIndex, jweRecipientHdr);

  // Set the Shared Unprotected Header:  {"jku":"https://server.example.com/keys.jwks"}
  final jweUnprotHdr = CkJsonObject();
  jweUnprotHdr.appendString('jku', 'https://server.example.com/keys.jwks');
  jwe.setUnprotectedHeader(jweUnprotHdr);

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

  // OK.. everything has been specified.
  // Now encrypt.  
  // Indicate that we prefer the flattened JSON serialization.
  jwe.preferFlattened = true;
  final String strJwe;
  try {
    strJwe = jwe.encrypt(plaintext, 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // The JWE is produced in the most compact form possible (a single line).
  // Let's load it into a JSON object and examine in a non-compact pretty-printed format:
  final jsonTemp = CkJsonObject();
  jsonTemp.load(strJwe);
  jsonTemp.emitCompact = false;
  print(jsonTemp.emit());

  // The JWE looks like this:
  // (Note: Because of random values used in the encryption process, your encrypted results will be different.)

  // 	{ 
  // 	  "protected": "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
  // 	  "unprotected": { 
  // 	    "jku": "https://server.example.com/keys.jwks"
  // 	  },
  // 	  "header": { 
  // 	    "alg": "A128KW",
  // 	    "kid": "7"
  // 	  },
  // 	  "encrypted_key": "FW7z9VxOvnF2ClicvUT4HTeqcdyh90C6qytfEFJsOb77FOwTfYrc3w",
  // 	  "iv": "O6Ly5-eML3zTs-_fNX3D5Q",
  // 	  "ciphertext": "Q8NLmeac9JhLh0CQPuG_7D9wVDb55eToCh0g5-FQ4M0",
  // 	  "tag": "slzlo6-J9C7wSDF4dh_kBg"
  // 	} 

  // Now decrypt......................................

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

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

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

  print('original text decrypted with AES key wrap key: ');
  print(originalPlaintext);

  // ---------------------------------------------------------------------------------
  // It should also be possible to decrypt the flattened JWE as shown in RFC 7516, Appendix A.5
  // because it was produced using the same key.

  final sbJwe = CkStringBuilder();

  sbJwe.append('{');
  sbJwe.append('"protected":');
  sbJwe.append('"eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",');
  sbJwe.append('"unprotected":');
  sbJwe.append('{"jku":"https://server.example.com/keys.jwks"},');
  sbJwe.append('"header":');
  sbJwe.append('{"alg":"A128KW","kid":"7"},');
  sbJwe.append('"encrypted_key":');
  sbJwe.append('"6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ",');
  sbJwe.append('"iv":');
  sbJwe.append('"AxY8DCtDaGlsbGljb3RoZQ",');
  sbJwe.append('"ciphertext":');
  sbJwe.append('"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY",');
  sbJwe.append('"tag":');
  sbJwe.append('"Mz-VPPyU4RlcuYv1IwIvzw"');
  sbJwe.append('}');

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

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

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

  print('original text decrypted from published flattened JWE: ');
  print(originalPlaintext);

  // The output:

  // original text decrypted with AES key wrap key: 
  // Live long and prosper.
  // original text decrypted from published flattened JWE: 
  // Live long and prosper.
}