对称加密-java实现

主要步骤如下：

1.利用SecretKeyFactory.getInstance("加密算法")创建密钥工厂，加密算法如"DES","AES"等

2.用new DESKeySpec(原始密钥)产生密钥对象，原始密钥是byte[]类型的

3.用密钥工厂的generateSecret(密钥对象)方法把密钥对象转换成规范的密钥对象

4.用new SecureRandom()或者用new IvParameterSpec(向量)生成一个可信任的随机数源

5.用Cipher.getInstance(“加密算法/加密模式/填充模式”)产生加密解密对象

6.用cipher.init(加密解密模型，规范密钥，随机数)初始化加密解密对象

7.用cipher.doFinal(数据)执行加密解密操作

代码如下：

    //加密
    private  byte[] desEncrypt(byte[] data, byte[] key) throws Exception {
         SecureRandom sr = new SecureRandom();
         DESKeySpec dks = new DESKeySpec(key);
         SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
         SecretKey securekey = keyFactory.generateSecret(dks);
         Cipher cipher = Cipher.getInstance("DES");
         cipher.init(1, securekey, sr);
         return cipher.doFinal(data);
     }
     //解密
     private  byte[] desDecrypt(byte[] data, byte[] key) throws Exception {
         SecureRandom sr = new SecureRandom();
         DESKeySpec dks = new DESKeySpec(key);
         SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
         SecretKey securekey = keyFactory.generateSecret(dks);
         Cipher cipher = Cipher.getInstance("DES");
         cipher.init(2, securekey, sr);
         return cipher.doFinal(data);
     }

因为加密完数据时byte[]类型的，因此使用sun.misc包下的BASE64Encoder类将二进制类型编码转换成String，如：

String str = (new BASE64Encoder()).encode(bt);