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

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     * *
* @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(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。

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
**/

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