对称加密算法

分类： 算法（常用+加密）2009-10-28 10:14182人阅读评论(0)收藏举报

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个字节共位,是DES算法的工作密钥;Data也为8个字节位,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算法把位的明文输入块变为位的密文输出块,它所使用的密钥也是位。

通过java代码实现如下：Coder类见 单向加密算法 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  *  *

 * 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 http://.../docs/technotes/guides/security/SunProviders.html

Document

 *  *

 * @author 梁栋  * @version 1.0  * @since 1.0  */

 public abstract class DESCoder extends Coder {  /**

 * ALGORITHM 算法

 * 可替换为以下任意一种算法，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 = new SecretKeySpec(key, ALGORITHM); 替换 *

* DESKeySpec dks = new DESKeySpec(key);

* SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); * SecretKey secretKey = keyFactory.generateSecret(dks); * */

public static final String ALGORITHM = \"DES\"; /**

* 转换密钥

 *

 * @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(decryptBASE(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(decryptBASE(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(decryptBASE(seed));  } else {

 secureRandom = new SecureRandom();  }

 KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM);  kg.init(secureRandom);

 SecretKey secretKey = kg.generateKey();  return encryptBASE(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.encryptBASE(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。 Java代码

 /**

 * 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  **/