Java加密技术篇（二）对称加密算法（DES&AES）

 接下来我们介绍对称加密算法，最常用的莫过于DES数据加密算法。 
DES 
DES-Data Encryption Standard,即数据加密算法。是IBM公司于1975年研究成功并公开发表的。DES算法的入口参数有三个:Key、Data、Mode。其中Key为8个字节共64位,是DES算法的工作密钥;Data也为8个字节64位,是要被加密或被解密的数据;Mode为DES的工作方式,有两种:加密或解密。 
　　DES算法把64位的明文输入块变为64位的密文输出块,它所使用的密钥也是64位。 

 

通过java代码实现如下：

 import java.security.InvalidKeyException;
 import java.security.Key;
 import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;
 import java.security.spec.InvalidKeySpecException;
 import java.util.Arrays;

 import javax.crypto.Cipher;
 import javax.crypto.KeyGenerator;
 import javax.crypto.SecretKey;
 import javax.crypto.SecretKeyFactory;
 import javax.crypto.spec.DESKeySpec;
 import javax.crypto.spec.SecretKeySpec;

 import org.apache.commons.codec.binary.Base64;
 import org.apache.commons.codec.binary.Hex;

 /**对称加密算法DES&AES
  * @description: TODO
  * @author Somnus
  * date 2015年4月8日 下午2:10:44
  */
 public class DESUtil {
     /**
      * ALGORITHM 算法 <br>
      * 可替换为以下任意一种算法，同时key值的size相应改变。
      *
      * <pre>
      * DES                  key size must be equal to 56
      * DESede(TripleDES)    key size must be equal to 112 or 168
      * AES                  key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
      * Blowfish             key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
      * RC2                  key size must be between 40 and 1024 bits
      * RC4(ARCFOUR)         key size must be between 40 and 1024 bits
      * </pre>
      *
      * 在Key keyGenerator(byte[] key)方法中使用下述代码
      * <code>SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);</code> 替换
      * <code>
      * DESKeySpec desKey = new DESKeySpec(key);
      * SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
      * SecretKey secretKey = keyFactory.generateSecret(desKey);
      * </code>
      */
     public static final String ALGORITHM = "DES";
     //算法名称/加密模式/填充方式
     //DES共有四种工作模式-->>ECB：电子密码本模式、CBC：加密分组链接模式、CFB：加密反馈模式、OFB：输出反馈模式
     public static final String CIPHER_ALGORITHM = "DES/ECB/NoPadding";

     /**
      *
      * 生成密钥key对象
      * @param KeyStr 密钥字符串
      * @return 密钥对象
      * @throws InvalidKeyException
      * @throws NoSuchAlgorithmException
      * @throws InvalidKeySpecException
      * @throws Exception
      */
     private static SecretKey keyGenerator(byte[] key) throws Exception {
         DESKeySpec desKey = new DESKeySpec(key);
         //创建一个密匙工厂，然后用它把DESKeySpec转换成
         SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
         SecretKey securekey = keyFactory.generateSecret(desKey);

         /*当使用其他对称加密算法时，如AES、Blowfish等算法时，用下述代码替换上述三行代码 */
         /*SecretKey secretKey = new SecretKeySpec(keyStr.getBytes(),KEY_ALGORITHM);*/
         return securekey;
     }

     /**
      * 加密数据
      * @param data 待加密数据
      * @param key 密钥
      * @return 加密后的数据
      */
     public static String encrypt(String data, String keyStr) throws Exception {
         Key deskey = keyGenerator(Base64.decodeBase64(keyStr));
         // 实例化Cipher对象，它用于完成实际的加密操作
         Cipher cipher = Cipher.getInstance(ALGORITHM);
         // 初始化Cipher对象，设置为加密模式
         cipher.init(Cipher.ENCRYPT_MODE, deskey);
         byte[] buff = cipher.doFinal(data.getBytes());
         System.out.println(Arrays.toString(buff));
         // 执行加密操作。加密后的结果通常都会用Base64编码进行传输
         return Hex.encodeHexString(buff);
     }

     /**
      * 解密数据
      * @param data 待解密数据
      * @param key 密钥
      * @return 解密后的数据
      */
     public static String decrypt(String data, String keyStr) throws Exception {
         Key deskey = keyGenerator(Base64.decodeBase64(keyStr));
         Cipher cipher = Cipher.getInstance(ALGORITHM);
         //初始化Cipher对象，设置为解密模式
         cipher.init(Cipher.DECRYPT_MODE, deskey);
         // 执行解密操作
         byte[] buff = cipher.doFinal(Hex.decodeHex(data.toCharArray()));
         System.out.println(Arrays.toString(buff));
         return new String(buff);
     }
     /**
      * 生成密钥
      * @return
      * @throws Exception
      */
     public static String initKey() throws Exception {
         return initKey(null);
     }
     /**
     * 生成密钥
     * @param seed
     * @return
     * @throws Exception
     */
    public static String initKey(String seed) throws Exception {
        SecureRandom secureRandom = null;
        if (seed != null) {
            secureRandom = new SecureRandom(Base64.decodeBase64(seed));
        } else {
            secureRandom = new SecureRandom();
        }
        KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM);
        kg.init(secureRandom);
        SecretKey secretKey = kg.generateKey();
        return Base64.encodeBase64String(secretKey.getEncoded());
    }
     public static void main(String[] args) throws Exception {
         String key = initKey();
         System.out.println(key+"size:"+Base64.decodeBase64(key).length);

         String source = "Somnus";
         System.out.println("原文: " + source);

         String encryptData = encrypt(source, key);
         System.out.println("加密后: " + encryptData);

         String decryptData = decrypt(encryptData, key);
         System.out.println("解密后: " + decryptData);
     }
 }

得到的输出内容如下： 

 5uMCAYNX9OY=size:8
 原文: Somnus
 [40, 72, 46, 74, 49, 99, 10, 119]
 加密后: 28482e4a31630a77
 [83, 111, 109, 110, 117, 115]
 解密后: Somnus

    由控制台得到的输出，我们能够比对加密、解密后结果一致。这是一种简单的加密解密方式，只有一个密钥。 
    其实DES有很多同胞兄弟，如DESede(TripleDES)、AES、Blowfish、RC2、RC4(ARCFOUR)。这里就不过多阐述了，大同小异，只要换掉ALGORITHM换成对应的值，同时做一个代码替换 SecretKey secretKey = new SecretKeySpec(key, ALGORITHM); 就可以了，此外就是密钥长度不同了。 

 /**
  * DES          key size must be equal to 56
  * DESede(TripleDES) key size must be equal to 112 or 168
  * AES          key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
  * Blowfish     key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
  * RC2          key size must be between 40 and 1024 bits
  * RC4(ARCFOUR) key size must be between 40 and 1024 bits
  **/

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