Java加密技术（二）

2009年11月01日 星期日 22:18

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：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());  
    }  
}

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);  
    }  
}

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

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