20、Java加密技术（二）——对称加密算法DES&AES

<转>http://snowolf.iteye.com/blog/380034
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。

java代码实现如下：

package org.nick.encrypt;
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;  
public class DESCoder extends Coder {
	 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.math.BigInteger;
import org.nick.encrypt.Coder;
import org.nick.encrypt.DESCoder;
public class Test
{
    public static void main(String[] str) 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);  
  
    }  
}

原文: DES
密钥: iv1h2VurtTQ=
加密后: skj6ss/YJNc=
解密后: DES

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。
/**
* 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
**/