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分类: Java

2010-11-11 11:25:00

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 
*  
*
  

* 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,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());  
    }  


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,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;  
 
/** 
*  
*/ 
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;

/**
*
*/
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 
**/ 

/**
* 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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