AES Encryption in Java

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Code:

package win.text.util;

import java.security.MessageDigest;
import java.security.Security;

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

import org.apache.commons.codec.binary.Base64;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

/**
* Utility class, providing AES encryption and decryption
* @required: bcprov-jdk16-146.jar, (http://www.java2s.com/Code/Jar/b/Downloadbcprovjdk16146jar.htm)
* @required: commons-codec-1.4.jar, (http://commons.apache.org/proper/commons-codec/download_codec.cgi)
* @author psupawa@gmail.com
*/
public class CipherUtils
{
   // Declare variables
   private Cipher cipher;
   private MessageDigest digest;
   private IvParameterSpec ivSpec;
   private SecretKeySpec keySpec;
   private String keyString = "thisIsASecretKeyLongString32bits";
   private String ivString = "thisIsAnIV16bits";
   
   /**
    * Constructor
    * @throws Exception
    */
   public CipherUtils() throws Exception {
       init();
   }
   
   /**
    * Constructor
    * @param keyString
    * @param ivString
    * @throws Exception
    */
   public CipherUtils(String keyString, String ivString) throws Exception {
       this.keyString = keyString;
       this.ivString = ivString;
       init();
   }
   
   /**
    * Initialize system
    * @throws Exception
    */
   public void init() throws Exception {
       Security.addProvider(new BouncyCastleProvider());        
       digest = MessageDigest.getInstance("SHA-256");
       digest.update(keyString.getBytes());
       byte[] key = new byte[ivString.length()];
       System.arraycopy(digest.digest(), 0, key, 0, key.length);
       keySpec = new SecretKeySpec(key, "AES");
       cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
       IvParameterSpec zeroIv = new IvParameterSpec(new byte[ivString.length()]);
       cipher.init(Cipher.ENCRYPT_MODE, keySpec, zeroIv);
   }

   /**
    * Encrypt the string
    * @param strToEncrypt
    * @return encrypted string
    * @throws Exception
    */
   public String encrypt(String strToEncrypt) throws Exception {
       String encryptedString = null;
       ivSpec = new IvParameterSpec(cipher.doFinal(ivString.getBytes()), 0, ivString.length());
       cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
       byte[] encryptedByte = cipher.doFinal(strToEncrypt.getBytes());
       encryptedString = Base64.encodeBase64String(encryptedByte);
       return encryptedString.replaceAll("(\\r|\\n)", "");
   }

   /**
    * Decrypt the string
    * @param strToDecrypt
    * @return decrypted string
    * @throws Exception
    */
   public String decrypt(String strToDecrypt) throws Exception {
       String decryptedString = null;
       cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
       decryptedString = new String(cipher.doFinal(Base64.decodeBase64(strToDecrypt)));
       return decryptedString.replaceAll("(\\r|\\n)", "");
   }

   /**
    * @param args
    */
   public static void main(String args[]) {
       CipherUtils cu;
       final String strToEncrypt = "HelloWorld";
       String encryptedStr = null;
       try {
           System.out.println("Input : " + strToEncrypt);
           cu = new CipherUtils();
           encryptedStr = cu.encrypt(strToEncrypt);
           System.out.println("Encrypted : " + encryptedStr);
       
           String strToDecrypt = encryptedStr;
           String decryptedStr = cu.decrypt(strToDecrypt);
           System.out.println("Decrypted : " + decryptedStr);
       } catch (Exception e) {
           e.printStackTrace();
       }
   }
}