对称加密算法

 

原创作者: snowolf  

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：Coder类见 单向加密算法

Java代码

1. import java.security.Key; 
2. import java.security.SecureRandom; 
3. import javax.crypto.Cipher; 
4. import javax.crypto.KeyGenerator; 
5. import javax.crypto.SecretKey; 
6. import javax.crypto.SecretKeyFactory; 
7. import javax.crypto.spec.DESKeySpec; 
8. /**
9. * DES安全编码组件
10. *
11. *
12. * 支持 DES、DESede(TripleDES,就是3DES)、AES、Blowfish、RC2、RC4(ARCFOUR)
13. * DES                  key size must be equal to 56
14. * DESede(TripleDES)    key size must be equal to 112 or 168
15. * AES                  key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
16. * Blowfish             key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
17. * RC2                  key size must be between 40 and 1024 bits
18. * RC4(ARCFOUR)         key size must be between 40 and 1024 bits
19. * 具体内容 需要关注 JDK Document http://.../docs/technotes/guides/security/SunProviders.html
20. *
21. *
22. * @author 梁栋
23. * @version 1.0
24. * @since 1.0
25. */
26. public abstract class DESCoder extends Coder { 
27. /**
28.      * ALGORITHM 算法 
29.      * 可替换为以下任意一种算法，同时key值的size相应改变。
30.      *
31.      *
32.      * DES                  key size must be equal to 56
33.      * DESede(TripleDES)    key size must be equal to 112 or 168
34.      * AES                  key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
35.      * Blowfish             key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
36.      * RC2                  key size must be between 40 and 1024 bits
37.      * RC4(ARCFOUR)         key size must be between 40 and 1024 bits
38.      *
39.      *
40.      * 在Key toKey(byte[] key)方法中使用下述代码
41.      * SecretKey secretKey = new SecretKeySpec(key, ALGORITHM); 替换
42.      *
43.      * DESKeySpec dks = new DESKeySpec(key);
44.      * SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
45.      * SecretKey secretKey = keyFactory.generateSecret(dks);
46.      *
47.      */
48. public static final String ALGORITHM = "DES"; 
49. /**
50.      * 转换密钥
51.      *
52.      * @param key
53.      * @return
54.      * @throws Exception
55.      */
56. private static Key toKey(byte[] key) throws Exception { 
57.         DESKeySpec dks = new DESKeySpec(key); 
58.         SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); 
59.         SecretKey secretKey = keyFactory.generateSecret(dks); 
60. // 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
61. // SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);
62. return secretKey; 
63.     } 
64. /**
65.      * 解密
66.      *
67.      * @param data
68.      * @param key
69.      * @return
70.      * @throws Exception
71.      */
72. public static byte[] decrypt(byte[] data, String key) throws Exception { 
73.         Key k = toKey(decryptBASE64(key)); 
74.         Cipher cipher = Cipher.getInstance(ALGORITHM); 
75.         cipher.init(Cipher.DECRYPT_MODE, k); 
76. return cipher.doFinal(data); 
77.     } 
78. /**
79.      * 加密
80.      *
81.      * @param data
82.      * @param key
83.      * @return
84.      * @throws Exception
85.      */
86. public static byte[] encrypt(byte[] data, String key) throws Exception { 
87.         Key k = toKey(decryptBASE64(key)); 
88.         Cipher cipher = Cipher.getInstance(ALGORITHM); 
89.         cipher.init(Cipher.ENCRYPT_MODE, k); 
90. return cipher.doFinal(data); 
91.     } 
92. /**
93.      * 生成密钥
94.      *
95.      * @return
96.      * @throws Exception
97.      */
98. public static String initKey() throws Exception { 
99. return initKey(null); 
100.     } 
101. /**
102.      * 生成密钥
103.      *
104.      * @param seed
105.      * @return
106.      * @throws Exception
107.      */
108. public static String initKey(String seed) throws Exception { 
109.         SecureRandom secureRandom = null; 
110. if (seed != null) { 
111.             secureRandom = new SecureRandom(decryptBASE64(seed)); 
112.         } else { 
113.             secureRandom = new SecureRandom(); 
114.         } 
115.         KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM); 
116.         kg.init(secureRandom); 
117.         SecretKey secretKey = kg.generateKey(); 
118. return encryptBASE64(secretKey.getEncoded()); 
119.     } 
120. } 

延续上一个类的实现，我们通过MD5以及SHA对字符串加密生成密钥，这是比较常见的密钥生成方式。 
再给出一个测试类：

Java代码

1. import static org.junit.Assert.*; 
2. import org.junit.Test; 
3. /**
4. *
5. * @author 梁栋
6. * @version 1.0
7. * @since 1.0
8. */
9. public class DESCoderTest { 
10. @Test
11. public void test() throws Exception { 
12.         String inputStr = "DES"; 
13.         String key = DESCoder.initKey(); 
14.         System.err.println("原文:/t" + inputStr); 
15.         System.err.println("密钥:/t" + key); 
16. byte[] inputData = inputStr.getBytes(); 
17.         inputData = DESCoder.encrypt(inputData, key); 
18.         System.err.println("加密后:/t" + DESCoder.encryptBASE64(inputData)); 
19. byte[] outputData = DESCoder.decrypt(inputData, key); 
20.         String outputStr = new String(outputData); 
21.         System.err.println("解密后:/t" + outputStr); 
22.         assertEquals(inputStr, outputStr); 
23.     } 
24. } 

得到的输出内容如下：

Console代码

1. 原文: DES 
2. 密钥: f3wEtRrV6q0= 
3. 加密后:    C6qe9oNIzRY= 
4. 解密后:    DES 

    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。

Java代码

1. /**
2. * DES          key size must be equal to 56
3. * DESede(TripleDES) key size must be equal to 112 or 168
4. * AES          key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
5. * Blowfish     key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
6. * RC2          key size must be between 40 and 1024 bits
7. * RC4(ARCFOUR) key size must be between 40 and 1024 bits
8. **/