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：Coder类见 Java加密技术（一）

Java代码


import java.security.Key;

import java.security.SecureRandom;

import javax.crypto.Cipher;

import javax.crypto.KeyGenerator;

import javax.crypto.SecretKey;

import javax.crypto.SecretKeyFactory;

import javax.crypto.spec.DESKeySpec;

/**

* DES安全编码组件

*

* <pre>

* 支持 DES、DESede(TripleDES,就是3DES)、AES、Blowfish、RC2、RC4(ARCFOUR)

* 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

* 具体内容 需要关注 JDK Document http://.../docs/technotes/guides/security/SunProviders.html
* </pre>

*

* @author 梁栋

* @version 1.0

* @since 1.0

*/

public abstract class DESCoder extends Coder {

/**

* 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 toKey(byte[] key)方法中使用下述代码

* <code>SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);</code> 替换

* <code>

* DESKeySpec dks = new DESKeySpec(key);

* SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);

* SecretKey secretKey = keyFactory.generateSecret(dks);

* </code>

*/

public static final String ALGORITHM = "DES";

/**

* 转换密钥<br>

*

* @param key

* @return

* @throws Exception

*/

private static Key toKey(byte[] key) throws Exception {

DESKeySpec dks = new DESKeySpec(key);

SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);

SecretKey secretKey = keyFactory.generateSecret(dks);

// 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(key, ALGORITHM);

return secretKey;

}

/**

* 解密

*

* @param data

* @param key

* @return

* @throws Exception

*/

public static byte[] decrypt(byte[] data, String key) throws Exception {

Key k = toKey(decryptBASE64(key));

Cipher cipher = Cipher.getInstance(ALGORITHM);

cipher.init(Cipher.DECRYPT_MODE, k);

return cipher.doFinal(data);

}

/**

* 加密

*

* @param data

* @param key

* @return

* @throws Exception

*/

public static byte[] encrypt(byte[] data, String key) throws Exception {

Key k = toKey(decryptBASE64(key));

Cipher cipher = Cipher.getInstance(ALGORITHM);

cipher.init(Cipher.ENCRYPT_MODE, k);

return cipher.doFinal(data);

}

/**

* 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(decryptBASE64(seed));

} else {

secureRandom = new SecureRandom();

}

KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM);

kg.init(secureRandom);

SecretKey secretKey = kg.generateKey();

return encryptBASE64(secretKey.getEncoded());

}

}

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


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() throws Exception {

String inputStr = "DES";

String key = DESCoder.initKey();

System.err.println("原文:\t" + inputStr);

System.err.println("密钥:\t" + key);

byte[] inputData = inputStr.getBytes();

inputData = DESCoder.encrypt(inputData, key);

System.err.println("加密后:\t" + DESCoder.encryptBASE64(inputData));

byte[] outputData = DESCoder.decrypt(inputData, key);

String outputStr = new String(outputData);

System.err.println("解密后:\t" + outputStr);

assertEquals(inputStr, outputStr);

}

}

得到的输出内容如下：

Console代码


原文: DES

密钥: f3wEtRrV6q0=

加密后: C6qe9oNIzRY=

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。