加密算法使用（四）：AES的使用

AES是一种对称加密方式，比DES更为安全，用一个秘钥加密数据之后，可以用同一个秘钥对加密后的数据解密还原，以下是一套以字符串为例子的使用全过程演示，

用到了

commons-codec.jar

 package testEncrypt;

 import java.security.InvalidKeyException;
 import java.security.Key;
 import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;

 import javax.crypto.BadPaddingException;
 import javax.crypto.Cipher;
 import javax.crypto.IllegalBlockSizeException;
 import javax.crypto.KeyGenerator;
 import javax.crypto.NoSuchPaddingException;
 import javax.crypto.SecretKey;
 import javax.crypto.spec.SecretKeySpec;

 import org.apache.commons.codec.binary.Base64;
 //import sun.misc.BASE64Encoder;
 public class TestAesEncrypt {

     public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException {
         //随机生成密钥
         KeyGenerator keygen = KeyGenerator.getInstance("AES");
         //SecureRandom random = new SecureRandom(Base64.decodeBase64("abc"));
         SecureRandom random = new SecureRandom();
         keygen.init(random);
         Key key = keygen.generateKey();
         //获取秘钥字符串
         String key64Str = Base64.encodeBase64String(key.getEncoded());
         //要加密的数据
         String dataStr="da89gh9qj3ebg9babjdslgbuqgb&FTUG^(GB";
         System.out.println("要加密的数据："+dataStr);

         //还原秘钥字符串到秘钥byte数组
         byte[] keyByteArray = Base64.decodeBase64(key64Str);
         //重新形成秘钥，SecretKey是Key的子类
         SecretKey secretKey = new SecretKeySpec(keyByteArray, "AES");

         //初始化加密组件
         Cipher cipher = Cipher.getInstance("AES");
         cipher.init(Cipher.ENCRYPT_MODE, secretKey);  

         //加密后的数据，首先将字符串转为byte数组，然后加密，为便于保存先转为base64
         String encryptedDataStr = Base64.encodeBase64String(cipher.doFinal(dataStr.getBytes()));
         System.out.println("加密后的数据："+encryptedDataStr);

         //将加密组件的模式改为解密
         cipher.init(Cipher.DECRYPT_MODE, secretKey);
          //和上面的加密相反，先解base64，再解密，最后将byte数组转为字符串
          String decodeDataStr = new String(cipher.doFinal(Base64.decodeBase64(encryptedDataStr)));
          System.out.println("解密后的数据："+decodeDataStr);
     }

 }