title: How to extract certain fields from encrypted JSON string in Swift?
body: <p>I am integrating <code>Apple Pay</code> into my application. I have a service written in Java which actually takes the encrypted blob sent from my <code>iOS</code> App and decrypts it and sends it back.</p>
  
  <p>I am facing two problems here:</p>
  
  <ol>
  <li>Bigger Problem - My service only consumes XML payload and hence I need to convert the <code>JSON</code> payload to <code>XML</code> payload in my <code>iOS</code> app which I am not sure how to do.</li>
  <li>Smaller Problem - I am trying to extract the fields from this encrypted <code>JSON</code> payload and print it out on the console. </li>
  </ol>
  
  <p>Example: </p>
  
  <pre><code>let jsonBody = payment.token.paymentData
  print("jsonBody = \(jsonBody)")    !!! WORKS (prints encrypted data) !!!
  </code></pre>
  
  <p>However, I am not able to extract other parameters that are present in the paymentData dictionary as per the following link
    <a href="https://developer.apple.com/library/ios/documentation/PassKit/Reference/PaymentTokenJSON/PaymentTokenJSON.html" rel="nofollow">https://developer.apple.com/library/ios/documentation/PassKit/Reference/PaymentTokenJSON/PaymentTokenJSON.html</a></p>
  
  <p>Example:</p>
  
  <pre><code>let paymentDataDict:[String:String] = payment.token.paymentData
  for (key, value) in paymentDataDict {
      print("Dictionary key \(key) -  Dictionary value \(value)")
  }
  
  Error: Cannot convert value of type 'NSData' to specified type '[String : String]'
  </code></pre>
  
  <p>Source:</p>
  
  <pre><code> /*
       * This is the first method to be called by the passkit framework once the encrypted blob is received from the apple server.
       * Our implementation of the call back function below is calling payment service to decrypt the encrypted blob.
       * It then proceeds to call processPayment method to send this data down to payment service for authorization.
      */
      func paymentAuthorizationViewController(controller: PKPaymentAuthorizationViewController, didAuthorizePayment payment: PKPayment, completion: (PKPaymentAuthorizationStatus) -&gt; Void) {
          let decryptUrl = NSURL(string: "http://lvsdevwsv04-01.us.gspt.net:1801/public-api-service/v1.0/stores/TMSUS/payments/decryptblob.xml")  // Decryption URL
          let decryptRequest = NSMutableURLRequest(URL: decryptUrl!)
          decryptRequest.HTTPMethod = "POST"
          decryptRequest.setValue("application/json", forHTTPHeaderField: "Content-Type")
          decryptRequest.setValue("application/json", forHTTPHeaderField: "Accept")
          let jsonBody = payment.token.paymentData
          print("jsonBody = \(jsonBody)")
  
          //ERROR IN THE BELOW LINE
          let paymentDataDict:[String:String] = payment.token.paymentData
          for (key, value) in paymentDataDict {
              print("Dictionary key \(key) -  Dictionary value \(value)")
          }
  
          decryptRequest.HTTPBody = jsonBody
          let task = NSURLSession.sharedSession().dataTaskWithRequest(decryptRequest) {data, response, error in
              guard error == nil &amp;&amp; data != nil else {
                  print("error=\(error)")
                  return
              }
              if let httpStatus = response as? NSHTTPURLResponse where httpStatus.statusCode != 200 {
                  print("statuscode should be 200, but is \(httpStatus.statusCode)")
                  print("response = \(response)")
              } else {
                  let responseString = NSString(data: data!, en
  
      //code removed for brevity
  </code></pre>