Java加密技术（二）

    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：

import java.security.Key;

 import javax.crypto.Cipher;
 import javax.crypto.SecretKey;
 import javax.crypto.SecretKeyFactory;
 import javax.crypto.spec.DESKeySpec;

 /**
 * DES安全编码组件
 *
 * @author 梁栋
 * @version 1.0
 * @since 1.0
 */
 public abstract class DESCoder extends Coder {
     public static final String ALGORITHM = "DES";

     /**
     * 取得密钥
     *
     * @param key
     * @return
     * @throws Exception
     */
     public static byte[] getKey(byte[] key) throws Exception {
         return encryptSHA(encryptMD5(key));
    }

     /**
     * 加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
     public static byte[] encode(byte[] data, byte[] key) throws Exception {
         DESKeySpec dks = new DESKeySpec(key);
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);

        SecretKey secretKey = keyFactory.generateSecret(dks);

         return encode(data, secretKey);
    }

     /**
     * 加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
     public static byte[] encode(byte[] data, Key key) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);

         return cipher.doFinal(data);
    }

     /**
     * 解密
     *
     * @param str
     * @param key
     * @return
     * @throws Exception
     */
     public static byte[] decode(byte[] data, byte[] key) throws Exception {
         DESKeySpec dks = new DESKeySpec(key);

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

         return decode(data, secretKey);
    }

     /**
     * 解密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
     public static byte[] decode(byte[] data, Key key) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, key);

         return cipher.doFinal(data);
    }
}

import java.security.Key;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

/**
 * DES安全编码组件
 * 
 * @author 梁栋
 * @version 1.0
 * @since 1.0
 */
public abstract class DESCoder extends Coder {
	public static final String ALGORITHM = "DES";

	/**
	 * 取得密钥
	 * 
	 * @param key
	 * @return
	 * @throws Exception
	 */
	public static byte[] getKey(byte[] key) throws Exception {
		return encryptSHA(encryptMD5(key));
	}

	/**
	 * 加密
	 * 
	 * @param data
	 * @param key
	 * @return
	 * @throws Exception
	 */
	public static byte[] encode(byte[] data, byte[] key) throws Exception {
		DESKeySpec dks = new DESKeySpec(key);
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);

		SecretKey secretKey = keyFactory.generateSecret(dks);

		return encode(data, secretKey);
	}

	/**
	 * 加密
	 * 
	 * @param data
	 * @param key
	 * @return
	 * @throws Exception
	 */
	public static byte[] encode(byte[] data, Key key) throws Exception {
		Cipher cipher = Cipher.getInstance(ALGORITHM);
		cipher.init(Cipher.ENCRYPT_MODE, key);

		return cipher.doFinal(data);
	}

	/**
	 * 解密
	 * 
	 * @param str
	 * @param key
	 * @return
	 * @throws Exception
	 */
	public static byte[] decode(byte[] data, byte[] key) throws Exception {
		DESKeySpec dks = new DESKeySpec(key);

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

		return decode(data, secretKey);
	}

	/**
	 * 解密
	 * 
	 * @param data
	 * @param key
	 * @return
	 * @throws Exception
	 */
	public static byte[] decode(byte[] data, Key key) throws Exception {
		Cipher cipher = Cipher.getInstance(ALGORITHM);
		cipher.init(Cipher.DECRYPT_MODE, key);

		return cipher.doFinal(data);
	}
}

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：

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() {
         try {
             String inputStr = "DES";
             String key = "中文";
             byte[] keyBytes = DESCoder.getKey(key.getBytes());
             System.err.println("原文:\t" + inputStr);

             System.err.println("密钥:\t" + new String(keyBytes));

             byte[] inputData = inputStr.getBytes();
            inputData = DESCoder.encode(inputData, keyBytes);

             System.err.println("加密后:\t" + new String(inputData));

             byte[] outputData = DESCoder.decode(inputData, keyBytes);
             String outputStr = new String(outputData);

             System.err.println("解密后:\t" + outputStr);

            assertEquals(inputStr, outputStr);
         } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

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() {
		try {
			String inputStr = "DES";
			String key = "中文";
			byte[] keyBytes = DESCoder.getKey(key.getBytes());
			System.err.println("原文:\t" + inputStr);

			System.err.println("密钥:\t" + new String(keyBytes));

			byte[] inputData = inputStr.getBytes();
			inputData = DESCoder.encode(inputData, keyBytes);
			
			System.err.println("加密后:\t" + new String(inputData));
			
			byte[] outputData = DESCoder.decode(inputData, keyBytes);
			String outputStr = new String(outputData);
			
			System.err.println("解密后:\t" + outputStr);
			
			assertEquals(inputStr, outputStr);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

得到的输出内容如下：

原文: DES
密钥: ����.+�g�M[��=��
�g
加密后:    ���Yg)w�
解密后:    DES

原文:	DES
密钥:	����.+�g�M[��=��
�g
加密后:	���Yg)w�
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
 **/

/**
 * 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
 **/

    后续我们会介绍非对称加密算法，如RSA、ECC。