接下来我们介绍对称加密算法&＃xff0c;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&＃xff1a;Coder类见 Java加密算法&＃xff08;一&＃xff09;
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* * * 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*
* */
public abstract class DESCoder extends Coder {/*** ALGORITHM 算法
* 可替换为以下任意一种算法&＃xff0c;同时key值的size相应改变。* * * 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*
* * 在Key toKey(byte[] key)方法中使用下述代码* SecretKey secretKey &＃61; new SecretKeySpec(key, ALGORITHM); 替换* * DESKeySpec dks &＃61; new DESKeySpec(key);* SecretKeyFactory keyFactory &＃61; SecretKeyFactory.getInstance(ALGORITHM);* SecretKey secretKey &＃61; keyFactory.generateSecret(dks);* */public static final String ALGORITHM &＃61; "DES";/*** 转换密钥
* * &＃64;param key* &＃64;return* &＃64;throws Exception*/private static Key toKey(byte[] key) throws Exception {DESKeySpec dks &＃61; new DESKeySpec(key);SecretKeyFactory keyFactory &＃61; SecretKeyFactory.getInstance(ALGORITHM);SecretKey secretKey &＃61; keyFactory.generateSecret(dks);// 当使用其他对称加密算法时&＃xff0c;如AES、Blowfish等算法时&＃xff0c;用下述代码替换上述三行代码// SecretKey secretKey &＃61; new SecretKeySpec(key, ALGORITHM);return secretKey;}/*** 解密* * &＃64;param data* &＃64;param key* &＃64;return* &＃64;throws Exception*/public static byte[] decrypt(byte[] data, String key) throws Exception {Key k &＃61; toKey(decryptBASE64(key));Cipher cipher &＃61; Cipher.getInstance(ALGORITHM);cipher.init(Cipher.DECRYPT_MODE, k);return cipher.doFinal(data);}/*** 加密* * &＃64;param data* &＃64;param key* &＃64;return* &＃64;throws Exception*/public static byte[] encrypt(byte[] data, String key) throws Exception {Key k &＃61; toKey(decryptBASE64(key));Cipher cipher &＃61; Cipher.getInstance(ALGORITHM);cipher.init(Cipher.ENCRYPT_MODE, k);return cipher.doFinal(data);}/*** 生成密钥* * &＃64;return* &＃64;throws Exception*/public static String initKey() throws Exception {return initKey(null);}/*** 生成密钥* * &＃64;param seed* &＃64;return* &＃64;throws Exception*/public static String initKey(String seed) throws Exception {SecureRandom secureRandom &＃61; null;if (seed !&＃61; null) {secureRandom &＃61; new SecureRandom(decryptBASE64(seed));} else {secureRandom &＃61; new SecureRandom();}KeyGenerator kg &＃61; KeyGenerator.getInstance(ALGORITHM);kg.init(secureRandom);SecretKey secretKey &＃61; kg.generateKey();return encryptBASE64(secretKey.getEncoded());}
}
延续上一个类的实现&＃xff0c;我们通过MD5以及SHA对字符串加密生成密钥&＃xff0c;这是比较常见的密钥生成方式。
再给出一个测试类&＃xff1a;
import static org.junit.Assert.*;import org.junit.Test;/***
*DES测试* */
public class DESCoderTest {&＃64;Testpublic void test() throws Exception {String inputStr &＃61; "DES";String key &＃61; DESCoder.initKey();System.err.println("原文:\t" &＃43; inputStr);System.err.println("密钥:\t" &＃43; key);byte[] inputData &＃61; inputStr.getBytes();inputData &＃61; DESCoder.encrypt(inputData, key);System.err.println("加密后:\t" &＃43; DESCoder.encryptBASE64(inputData));byte[] outputData &＃61; DESCoder.decrypt(inputData, key);String outputStr &＃61; new String(outputData);System.err.println("解密后:\t" &＃43; outputStr);assertEquals(inputStr, outputStr);}
}
得到的输出内容如下&＃xff1a;
原文: DES
密钥: f3wEtRrV6q0&＃61;加密后: C6qe9oNIzRY&＃61;解密后: DES
由控制台得到的输出&＃xff0c;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&＃xff0c;只有一个密钥。
其实DES有很多同胞兄弟&＃xff0c;如DESede(TripleDES)、AES、Blowfish、RC2、RC4(ARCFOUR)。这里就不过多阐述了&＃xff0c;大同小异&＃xff0c;只要换掉ALGORITHM换成对应的值&＃xff0c;同时做一个代码替换SecretKey secretKey &＃61; new SecretKeySpec(key, ALGORITHM);就可以了&＃xff0c;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**/
来源于&＃xff1a;http://snowolf.iteye.com/blog
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