import java.security.*; 
import javax.crypto.*; 
import javax.crypto.spec.*; 
import java.io.*;
public class Exp6_Rijndael_AES 
{
public static 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 static void main(String[] args) throws Exception
{ 
    String message="AES still rocks!!";

KeyGenerator kgen = KeyGenerator.getInstance("AES"); 
kgen.init(128);           
SecretKey skey = kgen.generateKey(); 
byte[] raw = skey.getEncoded();
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES"); 
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] encrypted = cipher.doFinal((args.length == 0 ? message :args[0]).getBytes()); System.out.println("encrypted string: " + asHex(encrypted));
cipher.init(Cipher.DECRYPT_MODE, skeySpec); 
byte[] original = cipher.doFinal(encrypted);
String originalString = new String(original);
System.out.println("Original string: " + originalString + " " + asHex(original));
}
}