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。