/*
 * Author: Mario Koenig
 *         Mario.Koenig@t-online.de
 *         http://www.synie.net/
 * This class is written on the fly. There is lots of error handling
 * to be done and so on. So if you need it, just use it as a basic
 * class.
 * As it's that basic, use it at your own risk.
 *
 * Also this class is written for usage with AESCryptLz for Open-
 * Laszlo. So you can use AESCryptLz to communicate with your Java
 * backend.
 *
 * I'm everything but a Java geek. So please forgive me that bad
 * source code ;-) Feel free to correct it and send me the modifi-
 * cations.
 *
 * Example usage:
 * # get the encrypted String 'str'
 * aesCrypt cr = new aesCrypt();
 * String decr = cr.decrypt(str);
 * # do something with the decrypted string
 * String encr = cr.encrypt(decr);
 * # give back the edited and reencrypted string
 */

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

public class aesCrypt {
    /*
     * The key used for the encryption
     */
    byte[] key = hexToByte("0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f");
    
    public String encrypt(String str)
    {
        try
        {
            /*
             * If the string is too short, add 0x00's
             */
            int buffl = str.length();
            while (buffl % 16 != 0)
            {
        	buffl++;
            }
            byte[] buff = new byte[buffl];
            for (int i = 0; i < str.length(); i++)
            {
            	buff[i] = str.getBytes()[i];
            }
            for (int i = str.length()+1; i < buff.length; i++)
            {
            	buff[i] = (byte)0x00;
            }
            
    	    /*
       	     * encrypt
       	     */
            Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
            cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"));
            byte[] encrypted = cipher.doFinal(buff);
            return asHex(encrypted);
        } catch (Exception err)
        {
            return err.toString();
        }	
    }
    
    public String decrypt(String str)
    {
        try
        {
       	    byte[] buff = hexToByte(str);
        	
            /*
             * decode
             */
            Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
            cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"));
            byte[] decrypted = cipher.doFinal(buff);
            
            // Trim the 0-bytes at the end
            int toDel;
            for (toDel = decrypted.length-1; toDel > 0; toDel--)
            {
            	if (decrypted[toDel] != (byte)0x00)
            	{
            	    toDel++;
            	    break;
            	}
            }
            byte[] decryptedWOnull = new byte[toDel];
            for (int i = 0; i < toDel; i++)
            {
            	decryptedWOnull[i] = decrypted[i];
            }
            return new String(decryptedWOnull);
        } catch (Exception err)
        {
            return err.toString();
        }	
    }
    
    public String asHex (byte buf[])
    {	
        StringBuffer strbuf = new StringBuffer(buf.length * 2);
        int i;
        for (i = 0; i < buf.length; i++)
        {
            if (((int) buf[i] & 0xff) < 0x10)
        	strbuf.append("0");
            strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
        }
        return strbuf.toString();
    }
    
    public byte[] hexToByte(String hex)
    {
    	hex = hex.replace(" ", "");
    	byte[] bts = new byte[hex.length() / 2];
    	for (int i = 0; i < bts.length; i++)
    	{
    		bts[i] = (byte) Integer.parseInt(hex.substring(2*i, 2*i+2), 16);
    	}
    	return bts;
    }
}