Java加密技术（三）

    除了DES，我们还知道有DESede(TripleDES,就是3DES)、AES、Blowfish、RC2、RC4(ARCFOUR)等多种对称加密方式，其实现方式大同小异，这里介绍对称加密的另一个算法——PBE

PBE
    PBE——Password-based encryption（基于密码的验证）。其特点在于口令由用户自己掌管，不借助任何物理媒体；采用随机数（这里我们叫做盐）杂凑多重加密等方法保证数据的安全性。是一种简便的加密方式。



通过java代码实现如下： Coder类见 Java加密技术（一）

import java.security.Key;
 import java.util.Random;

 import javax.crypto.Cipher;
 import javax.crypto.SecretKey;
 import javax.crypto.SecretKeyFactory;
 import javax.crypto.spec.PBEKeySpec;
 import javax.crypto.spec.PBEParameterSpec;

 /**
 * PBE安全编码组件
 *
 * @author 梁栋
 * @version 1.0
 * @since 1.0
 */
 public abstract class PBECoder extends Coder {
     /**
     * 支持以下任意一种算法
     *
     * <pre>
     * PBEWithMD5AndDES
     * PBEWithMD5AndTripleDES
     * PBEWithSHA1AndDESede
     * PBEWithSHA1AndRC2_40
     * </pre>
     */
     public static final String ALGORITHM = "PBEWITHMD5andDES";

     /**
     * 盐初始化
     *
     * @return
     * @throws Exception
     */
     public static byte[] initSalt() throws Exception {
         byte[] salt = new byte[8];
         Random random = new Random();
        random.nextBytes(salt);
         return salt;
    }

     /**
     * 转换密钥<br>
     *
     * @param password
     * @return
     * @throws Exception
     */
     private static Key toKey(String password) throws Exception {
         PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray());
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
        SecretKey secretKey = keyFactory.generateSecret(keySpec);

         return secretKey;
    }

     /**
     * 加密
     *
     * @param data
     *            数据
     * @param password
     *            密码
     * @param salt
     *            盐
     * @return
     * @throws Exception
     */
     public static byte[] encrypt(byte[] data, String password, byte[] salt)
             throws Exception {

        Key key = toKey(password);

         PBEParameterSpec paramSpec = new PBEParameterSpec(salt, 100);
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);

         return cipher.doFinal(data);

    }

     /**
     * 解密
     *
     * @param data
     *            数据
     * @param password
     *            密码
     * @param salt
     *            盐
     * @return
     * @throws Exception
     */
     public static byte[] decrypt(byte[] data, String password, byte[] salt)
             throws Exception {

        Key key = toKey(password);

         PBEParameterSpec paramSpec = new PBEParameterSpec(salt, 100);
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, key, paramSpec);

         return cipher.doFinal(data);

    }
}

import java.security.Key;
import java.util.Random;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

/**
 * PBE安全编码组件
 * 
 * @author 梁栋
 * @version 1.0
 * @since 1.0
 */
public abstract class PBECoder extends Coder {
	/**
	 * 支持以下任意一种算法
	 * 
	 * <pre>
	 * PBEWithMD5AndDES 
	 * PBEWithMD5AndTripleDES 
	 * PBEWithSHA1AndDESede
	 * PBEWithSHA1AndRC2_40
	 * </pre>
	 */
	public static final String ALGORITHM = "PBEWITHMD5andDES";

	/**
	 * 盐初始化
	 * 
	 * @return
	 * @throws Exception
	 */
	public static byte[] initSalt() throws Exception {
		byte[] salt = new byte[8];
		Random random = new Random();
		random.nextBytes(salt);
		return salt;
	}

	/**
	 * 转换密钥<br>
	 * 
	 * @param password
	 * @return
	 * @throws Exception
	 */
	private static Key toKey(String password) throws Exception {
		PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray());
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
		SecretKey secretKey = keyFactory.generateSecret(keySpec);

		return secretKey;
	}

	/**
	 * 加密
	 * 
	 * @param data
	 *            数据
	 * @param password
	 *            密码
	 * @param salt
	 *            盐
	 * @return
	 * @throws Exception
	 */
	public static byte[] encrypt(byte[] data, String password, byte[] salt)
			throws Exception {

		Key key = toKey(password);

		PBEParameterSpec paramSpec = new PBEParameterSpec(salt, 100);
		Cipher cipher = Cipher.getInstance(ALGORITHM);
		cipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);

		return cipher.doFinal(data);

	}

	/**
	 * 解密
	 * 
	 * @param data
	 *            数据
	 * @param password
	 *            密码
	 * @param salt
	 *            盐
	 * @return
	 * @throws Exception
	 */
	public static byte[] decrypt(byte[] data, String password, byte[] salt)
			throws Exception {

		Key key = toKey(password);

		PBEParameterSpec paramSpec = new PBEParameterSpec(salt, 100);
		Cipher cipher = Cipher.getInstance(ALGORITHM);
		cipher.init(Cipher.DECRYPT_MODE, key, paramSpec);

		return cipher.doFinal(data);

	}
}

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 PBECoderTest {

     @Test
     public void test() throws Exception {
         String inputStr = "abc";
         System.err.println("原文: " + inputStr);
         byte[] input = inputStr.getBytes();

         String pwd = "efg";
         System.err.println("密码: " + pwd);

         byte[] salt = PBECoder.initSalt();

         byte[] data = PBECoder.encrypt(input, pwd, salt);

         System.err.println("加密后: " + PBECoder.encryptBASE64(data));

         byte[] output = PBECoder.decrypt(data, pwd, salt);
         String outputStr = new String(output);

         System.err.println("解密后: " + outputStr);
        assertEquals(inputStr, outputStr);
    }

}

import static org.junit.Assert.*;

import org.junit.Test;

/**
 * 
 * @author 梁栋
 * @version 1.0
 * @since 1.0
 */
public class PBECoderTest {

	@Test
	public void test() throws Exception {
		String inputStr = "abc";
		System.err.println("原文: " + inputStr);
		byte[] input = inputStr.getBytes();

		String pwd = "efg";
		System.err.println("密码: " + pwd);

		byte[] salt = PBECoder.initSalt();

		byte[] data = PBECoder.encrypt(input, pwd, salt);

		System.err.println("加密后: " + PBECoder.encryptBASE64(data));

		byte[] output = PBECoder.decrypt(data, pwd, salt);
		String outputStr = new String(output);

		System.err.println("解密后: " + outputStr);
		assertEquals(inputStr, outputStr);
	}

}

控制台输出：

原文: abc
密码: efg
加密后: iCZ0uRtaAhE=

解密后: abc

原文: abc
密码: efg
加密后: iCZ0uRtaAhE=

解密后: abc

    后续我们会介绍非对称加密算法，如RSA、DSA、DH、ECC等。