title: Having issues with decrypting AES-GCM
body: <p>I've been trying to figure out my way around the java security/crypto libraries and i believe I've made some progress with understanding what's going on. I think I managed to get the encryption part working. In my encrypt method if i simply try to return 
  <code>return new String(encryptedText, "UTF-8");</code>
  I get some unreadable jumble which looks like encrypted text.
  The issue comes about when I try to instead of returning that, going on and calling decrypt and going cleartext --> encrypt --> decrypt
  here is everything i have</p>
  
  <pre><code>import javax.crypto.*;
  import java.security.*;
  import java.io.UnsupportedEncodingException;
  
  public class AES256_GCM {
  
  public String encrypt(String cleartext) {
  
      try 
      {
          // encoding format needs thought
          byte[] clearTextbytes = cleartext.getBytes("UTF-8");
          final SecureRandom secureKeyRandomness = SecureRandom.getInstanceStrong();
          final KeyGenerator AES_keyInstance = KeyGenerator.getInstance("AES");
          AES_keyInstance.init(128, secureKeyRandomness);
          final SecretKey secretKey = AES_keyInstance.generateKey();
          final Cipher AES_cipherInstance = Cipher.getInstance("AES/GCM/NoPadding");
          AES_cipherInstance.init(Cipher.ENCRYPT_MODE, secretKey);
          byte[] encryptedText = AES_cipherInstance.doFinal(clearTextbytes);
          return decrypt(encryptedText, secretKey);
      } 
      catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException | UnsupportedEncodingException e) 
      {
          e.printStackTrace();
      }
      return "something went wrong with encrypt";
  } // encrypt.
  
  public String decrypt(byte[] encryptedText, SecretKey secretKey) {
      try 
      {
          final Cipher AES_cipherInstance = Cipher.getInstance("AES/GCM/NoPadding");
          AES_cipherInstance.init(Cipher.DECRYPT_MODE, secretKey);
          byte[] decryptedText = AES_cipherInstance.doFinal(encryptedText);
          return new String(decryptedText, "UTF-8");
      } 
      catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException | UnsupportedEncodingException e) 
      {
          e.printStackTrace();
      }
      return "something went wrong with decrypt";
  } // decrypt.
  
  } // AES256_GCM.
  </code></pre>
  
  <p>So i call encrypt with some cleartext and try to return back the cleartext to make sure it works. Here's what im dealing with, Anything with javafx in there is probably irrelevant. I get no issues returning the encrypted string, its only the decrypted string throwing this.</p>
  
  <p>"something went wrong with decrypt" is returned followed by:</p>
  
  <pre><code>    java.security.InvalidKeyException: Parameters missing
      at com.sun.crypto.provider.CipherCore.init(CipherCore.java:470)
      at com.sun.crypto.provider.AESCipher.engineInit(AESCipher.java:313)
      at javax.crypto.Cipher.implInit(Cipher.java:801)
      at javax.crypto.Cipher.chooseProvider(Cipher.java:863)
      at javax.crypto.Cipher.init(Cipher.java:1248)
      at javax.crypto.Cipher.init(Cipher.java:1185)
      at PackageName.AES256_GCM.decrypt(AES256_GCM.java:49)
      at PackageName.AES256_GCM.encrypt(AES256_GCM.java:36)
      at com.javafxpractice.PackageName.letsEncrypt.letsEnc(letsEncrypt.java:10)
      at com.javafxpractice.PackageName.Controller.onClicked(Controller.java:24)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at sun.reflect.misc.Trampoline.invoke(Unknown Source)
      at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
      at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
      at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
      at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
      at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
      at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
      at javafx.event.Event.fireEvent(Event.java:198)
      at javafx.scene.Node.fireEvent(Node.java:8413)
      at javafx.scene.control.Button.fire(Button.java:185)
      at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
      at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
      at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
      at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
      at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
      at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
      at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
      at javafx.event.Event.fireEvent(Event.java:198)
      at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
      at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
      at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
      at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
      at java.security.AccessController.doPrivileged(Native Method)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$353(GlassViewEventHandler.java:432)
      at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
      at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
      at com.sun.glass.ui.View.notifyMouse(View.java:937)
      at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
      at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
      at java.lang.Thread.run(Unknown Source)
  java.security.InvalidKeyException: Parameters missing
      at com.sun.crypto.provider.CipherCore.init(CipherCore.java:470)
      at com.sun.crypto.provider.AESCipher.engineInit(AESCipher.java:313)
      at javax.crypto.Cipher.implInit(Cipher.java:801)
      at javax.crypto.Cipher.chooseProvider(Cipher.java:863)
      at javax.crypto.Cipher.init(Cipher.java:1248)
      at javax.crypto.Cipher.init(Cipher.java:1185)
      at PackageName.AES256_GCM.decrypt(AES256_GCM.java:49)
      at PackageName.AES256_GCM.encrypt(AES256_GCM.java:36)
      at com.javafxpractice.PackageName.letsEncrypt.letsEnc(letsEncrypt.java:10)
      at com.javafxpractice.PackageName.Controller.onEnter(Controller.java:32)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at sun.reflect.misc.Trampoline.invoke(Unknown Source)
      at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
      at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
      at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
      at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
      at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
      at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
      at javafx.event.Event.fireEvent(Event.java:198)
      at javafx.scene.Scene$KeyHandler.process(Scene.java:3964)
      at javafx.scene.Scene$KeyHandler.access$1800(Scene.java:3910)
      at javafx.scene.Scene.impl_processKeyEvent(Scene.java:2040)
      at javafx.scene.Scene$ScenePeerListener.keyEvent(Scene.java:2501)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:217)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:149)
      at java.security.AccessController.doPrivileged(Native Method)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleKeyEvent$352(GlassViewEventHandler.java:248)
      at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:247)
      at com.sun.glass.ui.View.handleKeyEvent(View.java:546)
      at com.sun.glass.ui.View.notifyKey(View.java:966)
      at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
      at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
      at java.lang.Thread.run(Unknown Source)
  </code></pre>