Java Card

package handson_crypto_aes;

import javacard.framework.*;
import javacard.security.*;
import javacardx.crypto.*;

/**
 *
 * ClassHandsOnCryptoAES
 *
 */

public class HandsOnCryptoAES extends javacard.framework.Applet
{

	//globals
	AESKey aesKey;
	Cipher cipherAES;
	RandomData random;
	static byte a[];
	final short dataOffset = (short) ISO7816.OFFSET_CDATA;

	//constructor
	private HandsOnCryptoAES (byte bArray[], short bOffset, byte bLength)
	{
		aesKey = (AESKey) KeyBuilder.buildKey(KeyBuilder.TYPE_AES, KeyBuilder.LENGTH_AES_128, false);
		cipherAES = Cipher.getInstance(Cipher.ALG_AES_BLOCK_128_CBC_NOPAD, false);
		a = new byte[ (short) 128];
		random.generateData(a, (short)0, (short)128);
		aesKey.setKey(a, (short) 0);
		register(bArray, (short) (bOffset + 1), bArray[bOffset]);
	}

	//install
	public static void install(byte bArray[], short bOffset, byte bLength)
	{
		new HandsOnCryptoAES (bArray, bOffset, bLength);
	}

	public void process(APDU apdu)
	{
		byte[] buf = apdu.getBuffer();
		if (selectingApplet())
		{
			return;
		}
		if (buf[ISO7816.OFFSET_CLA] != 0) ISOException.throwIt(ISO7816.SW_CLA_NOT_SUPPORTED);
		
		if (buf[ISO7816.OFFSET_INS] != (byte) (0xAA)) ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
		
		switch (buf[ISO7816.OFFSET_P1])
		{
		case (byte) 0x01:
			doAES(apdu);
			return;
		default:
			ISOException.throwIt(ISO7816.SW_WRONG_P1P2);
		}
	}


	private void doAES(APDU apdu)
	{
		
		byte b[] = apdu.getBuffer();
		
		short incomingLength = (short) (apdu.setIncomingAndReceive());
		if (incomingLength != 24) ISOException.throwIt(ISO7816.SW_WRONG_LENGTH);

		//perform encryption and append results in APDU Buffer a[] automatically 
		
		cipherAES.init(aesKey, Cipher.MODE_ENCRYPT);
		cipherAES.doFinal(b, (short) dataOffset, incomingLength, a, (short) (dataOffset + 24));
		cipherAES.init(aesKey, Cipher.MODE_DECRYPT);
		cipherAES.doFinal(b, (short) (dataOffset + 24), incomingLength, a, (short) (dataOffset + 48));

		// Send results
		apdu.setOutgoing();
		apdu.setOutgoingLength((short) 72);
		apdu.sendBytesLong(b, (short) dataOffset, (short) 72);
	}