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;
4. import javax.crypto.Cipher;
5. import javax.crypto.KeyGenerator;
6. import javax.crypto.SecretKey;
7. import javax.crypto.SecretKeyFactory;
8. import javax.crypto.spec.DESKeySpec;
11. /**
12. * DES安全编码组件
13. *
14. *

15. * 支持 DES、DESede(TripleDES,就是3DES)、AES、Blowfish、RC2、RC4(ARCFOUR)
16. * DES key size must be equal to 56
17. * DESede(TripleDES) key size must be equal to 112 or 168
18. * AES key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
19. * Blowfish key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
20. * RC2 key size must be between 40 and 1024 bits
21. * RC4(ARCFOUR) key size must be between 40 and 1024 bits
22. * 具体内容 需要关注 JDK Document http://.../docs/technotes/guides/security/SunProviders.html
23. *
24. *
25. * @author 梁栋
26. * @version 1.0
27. * @since 1.0
28. */
29. public abstract class DESCoder extends Coder {
30. /**
31. * ALGORITHM 算法
    
32. * 可替换为以下任意一种算法，同时key值的size相应改变。
33. *
34. *

35. * DES key size must be equal to 56
36. * DESede(TripleDES) key size must be equal to 112 or 168
37. * AES key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
38. * Blowfish key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
39. * RC2 key size must be between 40 and 1024 bits
40. * RC4(ARCFOUR) key size must be between 40 and 1024 bits
41. *
42. *
43. * 在Key toKey(byte[] key)方法中使用下述代码
44. * SecretKey secretKey = new SecretKeySpec(key, ALGORITHM); 替换
45. *
46. * DESKeySpec dks = new DESKeySpec(key);
47. * SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
48. * SecretKey secretKey = keyFactory.generateSecret(dks);
49. *
50. */
51. public static final String ALGORITHM = "DES";
53. /**
54. * 转换密钥
    
55. *
56. * @param key
57. * @return
58. * @throws Exception
59. */
60. private static Key toKey(byte[] key) throws Exception {
61. DESKeySpec dks = new DESKeySpec(key);
62. SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
63. SecretKey secretKey = keyFactory.generateSecret(dks);
65. // 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
66. // SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);
68. return secretKey;
69. }
71. /**
72. * 解密
73. *
74. * @param data
75. * @param key
76. * @return
77. * @throws Exception
78. */
79. public static byte[] decrypt(byte[] data, String key) throws Exception {
80. Key k = toKey(decryptBASE64(key));
82. Cipher cipher = Cipher.getInstance(ALGORITHM);
83. cipher.init(Cipher.DECRYPT_MODE, k);
85. return cipher.doFinal(data);
86. }
88. /**
89. * 加密
90. *
91. * @param data
92. * @param key
93. * @return
94. * @throws Exception
95. */
96. public static byte[] encrypt(byte[] data, String key) throws Exception {
97. Key k = toKey(decryptBASE64(key));
98. Cipher cipher = Cipher.getInstance(ALGORITHM);
99. cipher.init(Cipher.ENCRYPT_MODE, k);
101. return cipher.doFinal(data);
102. }
104. /**
105. * 生成密钥
106. *
107. * @return
108. * @throws Exception
109. */
110. public static String initKey() throws Exception {
111. return initKey(null);
112. }
114. /**
115. * 生成密钥
116. *
117. * @param seed
118. * @return
119. * @throws Exception
120. */
121. public static String initKey(String seed) throws Exception {
122. SecureRandom secureRandom = null;
124. if (seed != null) {
125. secureRandom = new SecureRandom(decryptBASE64(seed));
126. } else {
127. secureRandom = new SecureRandom();
128. }
130. KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM);
131. kg.init(secureRandom);
133. SecretKey secretKey = kg.generateKey();
135. return encryptBASE64(secretKey.getEncoded());
136. }
137. }

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.*;
3. import org.junit.Test;
5. /**
6. *
7. * @author 梁栋
8. * @version 1.0
9. * @since 1.0
10. */
11. public class DESCoderTest {
13. @Test
14. public void test() throws Exception {
15. String inputStr = "DES";
16. String key = DESCoder.initKey();
17. System.err.println("原文:\t" + inputStr);
19. System.err.println("密钥:\t" + key);
21. byte[] inputData = inputStr.getBytes();
22. inputData = DESCoder.encrypt(inputData, key);
24. System.err.println("加密后:\t" + DESCoder.encryptBASE64(inputData));
26. byte[] outputData = DESCoder.decrypt(inputData, key);
27. String outputStr = new String(outputData);
29. System.err.println("解密后:\t" + outputStr);
31. assertEquals(inputStr, outputStr);
32. }
33. }

得到的输出内容如下：

Console代码

1. 原文: DES
2. 密钥: f3wEtRrV6q0=
4. 加密后: C6qe9oNIzRY=
6. 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. **/