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public class DoAES extends Applet {

    static Cipher myCipher;
    static AESKey myAESKey;
    byte[] cipheredData = JCSystem.makeTransientByteArray((short) 0x10, JCSystem.CLEAR_ON_RESET);

    final static byte SET_KEY = (byte) 0x12;
    final static byte WRITE_TEXT = (byte) 0x04;
    final static byte READ_TEXT = (byte) 0xC0;

    private DoAES() {

        try {
            myCipher = Cipher.getInstance(Cipher.ALG_AES_BLOCK_128_ECB_NOPAD, false);
            myAESKey = (AESKey) KeyBuilder.buildKey(KeyBuilder.TYPE_AES,
                    KeyBuilder.LENGTH_AES_128, false);
        } catch (CryptoException e) {
            ISOException.throwIt(((CryptoException) e).getReason());
        }
    }

    public static void install(byte bArray[], short bOffset, byte bLength)
            throws ISOException {
        (new DoAES()).register();
    }

    public void process(APDU apdu) throws ISOException {
        if (selectingApplet()) {
            return;
        }

        byte[] buffer = apdu.getBuffer();

        if ((buffer[ISO7816.OFFSET_CLA] & 0x00FF) != 0x80) {
            ISOException.throwIt(ISO7816.SW_CLA_NOT_SUPPORTED);
        }

        try {
            switch (buffer[ISO7816.OFFSET_INS]) {

                case SET_KEY:
                    myAESKey.setKey(buffer, (short) ISO7816.OFFSET_CDATA);
                    myCipher.init(myAESKey, Cipher.MODE_ENCRYPT);
                    break;

                case WRITE_TEXT:
                    myCipher.doFinal(buffer, (short) ISO7816.OFFSET_CDATA, (short) 0x10, cipheredData, (short) 0);
                    break;

                case READ_TEXT:
                    Util.arrayCopyNonAtomic(cipheredData, (short) 0, buffer, (short) 0, (short) 0x10);
                    apdu.setOutgoingAndSend((short) 0, (short) 0x10);
                    break;

                default:
                    ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
            }
        } catch (CryptoException e) {
            ISOException.throwIt(((CryptoException) e).getReason());
        }
    }
}