/*********************************************************************************
 *  TotalCross Software Development Kit                                          *
 *  Copyright (C) 2000-2012 SuperWaba Ltda.                                      *
 *  All Rights Reserved                                                          *
 *                                                                               *
 *  This library and virtual machine is distributed in the hope that it will     *
 *  be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of    *
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.                         *
 *                                                                               *
 *********************************************************************************/

package totalcross.crypto.cipher;

import java.security.GeneralSecurityException;
import javax.crypto.spec.*;
import totalcross.crypto.*;

/**
 * This class implements the AES cryptographic cipher.
 *
 * <p>If you get a <code>totalcross.crypto.CryptoException: Illegal key size</code>, you must download the strong cryptography files from Oracle 
 * site. In order to do that, go to the ReadMe file whole link is below the download link. In this file, search for "Unlimited Strength Java 
 * Cryptography Extension" and follow the instructions. 
 */
public class AESCipher extends Cipher
{
   /**
    * Returns the name of the algorithm.
    * 
    * @return "AES".
    */
   public final String getAlgorithm()
   {
      return "AES";
   }

   /**
    * Returns the block length.
    * 
    * @return Always returns 16.
    */
   public final int getBlockLength()
   {
      // Applet may support 16 or 32, like axtls
      // javax.crypto.Cipher cipher = (javax.crypto.Cipher)cipherRef;
      // return (cipher != null) ? cipher.getBlockSize() : 16;
      return 16;
   }
   
   protected final void doReset() throws NoSuchAlgorithmException, CryptoException
   {
      String transf = "AES";
      switch (chaining)
      {
         case CHAINING_NONE:
            transf += "/NONE";
            break;
         case CHAINING_ECB:
            transf += "/ECB";
            break;
         case CHAINING_CBC:
            transf += "/CBC";
            break;
      }
      switch (padding)
      {
         case PADDING_NONE:
            transf += "/NoPadding";
            break;
         case PADDING_PKCS1:
            transf += "/PKCS1Padding";
            break;
         case PADDING_PKCS5:
            transf += "/PKCS5Padding";
      }
      
      try
      {
         javax.crypto.Cipher cipher = javax.crypto.Cipher.getInstance(transf);
         cipherRef = cipher;
         
         keyRef = new SecretKeySpec(((AESKey)key).getData(), "AES");
         
         int mode = operation == OPERATION_ENCRYPT ? javax.crypto.Cipher.ENCRYPT_MODE : javax.crypto.Cipher.DECRYPT_MODE;
         cipher.init(mode, (java.security.Key)keyRef, iv == null ? null : new IvParameterSpec(iv));
         if (iv == null)
            iv = cipher.getIV();
      }
      catch (java.security.NoSuchAlgorithmException e)
      {
         throw new NoSuchAlgorithmException(e.getMessage());
      }
      catch (GeneralSecurityException e)
      {
         throw new CryptoException(e.getMessage());
      }
   }
   
   protected final byte[] process(byte[] data) throws CryptoException
   {
      try
      {
         javax.crypto.Cipher cipher = (javax.crypto.Cipher)cipherRef;
         return cipher.doFinal(data);
      }
      catch (GeneralSecurityException e)
      {
         throw new CryptoException(e.getMessage());
      }
   }
   
   protected final boolean isKeySupported(Key key, int operation)
   {
      return key instanceof AESKey;
   }
   
   protected final boolean isChainingSupported(int chaining)
   {
      return chaining == CHAINING_ECB || chaining == CHAINING_CBC;
   }
   
   protected final boolean isPaddingSupported(int padding)
   {
      return padding == PADDING_PKCS5;
   }
}