Java加密技术（二）

Java加密技术（二）关键字: des, 对称加密算法    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：
Java代码

1. import java.security.Key;  
2.   
3. import javax.crypto.Cipher;  
4. import javax.crypto.SecretKey;  
5. import javax.crypto.SecretKeyFactory;  
6. import javax.crypto.spec.DESKeySpec;  
7.   
8. /**
9. * DES安全编码组件
10. *
11. * @author 梁栋
12. * @version 1.0
13. * @since 1.0
14. */  
15. public abstract class DESCoder extends Coder {  
16.     public static final String ALGORITHM = "DES";  
17.   
18.     /**
19.       * 取得密钥
20.       *
21.       * @param key
22.       * @return
23.       * @throws Exception
24.       */  
25.     public static byte[] getKey(byte[] key) throws Exception {  
26.         return encryptSHA(encryptMD5(key));  
27.      }  
28.   
29.     /**
30.       * 加密
31.       *
32.       * @param data
33.       * @param key
34.       * @return
35.       * @throws Exception
36.       */  
37.     public static byte[] encode(byte[] data, byte[] key) throws Exception {  
38.          DESKeySpec dks = new DESKeySpec(key);  
39.          SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);  
40.   
41.          SecretKey secretKey = keyFactory.generateSecret(dks);  
42.   
43.         return encode(data, secretKey);  
44.      }  
45.   
46.     /**
47.       * 加密
48.       *
49.       * @param data
50.       * @param key
51.       * @return
52.       * @throws Exception
53.       */  
54.     public static byte[] encode(byte[] data, Key key) throws Exception {  
55.          Cipher cipher = Cipher.getInstance(ALGORITHM);  
56.          cipher.init(Cipher.ENCRYPT_MODE, key);  
57.   
58.         return cipher.doFinal(data);  
59.      }  
60.   
61.     /**
62.       * 解密
63.       *
64.       * @param str
65.       * @param key
66.       * @return
67.       * @throws Exception
68.       */  
69.     public static byte[] decode(byte[] data, byte[] key) throws Exception {  
70.          DESKeySpec dks = new DESKeySpec(key);  
71.   
72.          SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);  
73.          SecretKey secretKey = keyFactory.generateSecret(dks);  
74.   
75.         return decode(data, secretKey);  
76.      }  
77.   
78.     /**
79.       * 解密
80.       *
81.       * @param data
82.       * @param key
83.       * @return
84.       * @throws Exception
85.       */  
86.     public static byte[] decode(byte[] data, Key key) throws Exception {  
87.          Cipher cipher = Cipher.getInstance(ALGORITHM);  
88.          cipher.init(Cipher.DECRYPT_MODE, key);  
89.   
90.         return cipher.doFinal(data);  
91.      }  
92. }  

import java.security.Key; import javax.crypto.Cipher; import javax.crypto.SecretKey; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.DESKeySpec; /** * DES安全编码组件 * * @author 梁栋 * @version 1.0 * @since 1.0 */ public abstract class DESCoder extends Coder { public static final String ALGORITHM = "DES"; /** * 取得密钥 * * @param key * @return * @throws Exception */ public static byte[] getKey(byte[] key) throws Exception { return encryptSHA(encryptMD5(key)); } /** * 加密 * * @param data * @param key * @return * @throws Exception */ public static byte[] encode(byte[] data, byte[] key) throws Exception { DESKeySpec dks = new DESKeySpec(key); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); SecretKey secretKey = keyFactory.generateSecret(dks); return encode(data, secretKey); } /** * 加密 * * @param data * @param key * @return * @throws Exception */ public static byte[] encode(byte[] data, Key key) throws Exception { Cipher cipher = Cipher.getInstance(ALGORITHM); cipher.init(Cipher.ENCRYPT_MODE, key); return cipher.doFinal(data); } /** * 解密 * * @param str * @param key * @return * @throws Exception */ public static byte[] decode(byte[] data, byte[] key) throws Exception { DESKeySpec dks = new DESKeySpec(key); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); SecretKey secretKey = keyFactory.generateSecret(dks); return decode(data, secretKey); } /** * 解密 * * @param data * @param key * @return * @throws Exception */ public static byte[] decode(byte[] data, Key key) throws Exception { Cipher cipher = Cipher.getInstance(ALGORITHM); cipher.init(Cipher.DECRYPT_MODE, key); return cipher.doFinal(data); } }
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.   
3. import org.junit.Test;  
4.   
5. /**
6. *
7. * @author 梁栋
8. * @version 1.0
9. * @since 1.0
10. */  
11. public class DESCoderTest {  
12.   
13.     @Test  
14.     public void test() {  
15.         try {  
16.              String inputStr = "DES";  
17.              String key = "中文";  
18.             byte[] keyBytes = DESCoder.getKey(key.getBytes());  
19.              System.err.println("原文:\t" + inputStr);  
20.   
21.              System.err.println("密钥:\t" + new String(keyBytes));  
22.   
23.             byte[] inputData = inputStr.getBytes();  
24.              inputData = DESCoder.encode(inputData, keyBytes);  
25.               
26.              System.err.println("加密后:\t" + new String(inputData));  
27.               
28.             byte[] outputData = DESCoder.decode(inputData, keyBytes);  
29.              String outputStr = new String(outputData);  
30.               
31.              System.err.println("解密后:\t" + outputStr);  
32.               
33.              assertEquals(inputStr, outputStr);  
34.          } catch (Exception e) {  
35.              e.printStackTrace();  
36.          }  
37.      }  
38. }  

import static org.junit.Assert.*; import org.junit.Test; /** * * @author 梁栋 * @version 1.0 * @since 1.0 */ public class DESCoderTest { @Test public void test() { try { String inputStr = "DES"; String key = "中文"; byte[] keyBytes = DESCoder.getKey(key.getBytes()); System.err.println("原文:\t" + inputStr); System.err.println("密钥:\t" + new String(keyBytes)); byte[] inputData = inputStr.getBytes(); inputData = DESCoder.encode(inputData, keyBytes); System.err.println("加密后:\t" + new String(inputData)); byte[] outputData = DESCoder.decode(inputData, keyBytes); String outputStr = new String(outputData); System.err.println("解密后:\t" + outputStr); assertEquals(inputStr, outputStr); } catch (Exception e) { e.printStackTrace(); } } }
得到的输出内容如下：
Console代码

1. 原文: DES  
2. 密钥: .+ g M[ =   
3. g  
4. 加密后:     Yg)w   
5. 解密后:     DES  

原文: DES 密钥: .+ g M[ = g 加密后: Yg)w 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. **/  

/** * 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 **/
    后续我们会介绍非对称加密算法，如RSA、ECC。