《DES对称加密的实现及其源代码》

package util;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import java.security.*;
import java.io.*;

/**
 * Created by IntelliJ IDEA.
 * User: Administrator
 * Date: Dec 4, 2003
 * Time: 9:29:19 PM
 * To change this template use Options | File Templates.

 *@author [email protected]
 * 该类是加密处理类.主要用来对数据进行加密,解密操作.
 */
public class DESEncryptUtil {
    /**
     * 获得DES加密的密钥。在交易处理的过程中应该定时更
     * 换密钥。需要JCE的支持，如果jdk版本低于1.4，则需要
     * 安装jce-1_2_2才能正常使用。
     * @return   Key  返回对称密钥
     * @throws java.security.NoSuchAlgorithmException
     * @see util.EncryptUtil 其中包括加密和解密的方法
     */
    public static Key getKey() throws NoSuchAlgorithmException {
        Security.insertProviderAt(new com.sun.crypto.provider.SunJCE(), 1);
        KeyGenerator generator = KeyGenerator.getInstance("DES");
        generator.init(new SecureRandom());
        Key key = generator.generateKey();
        return key;
    }

    /**
     * 将指定的数据根据提供的密钥进行加密
     * @param key  密钥
     * @param data 需要加密的数据
     * @return  byte[] 加密后的数据
     * @throws util.EncryptException
     */
    public static byte[] doEncrypt(Key key, byte[] data) throws EncryptException {
        try {
            //Get a cipher object
            Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");

            //Encrypt
            cipher.init(Cipher.ENCRYPT_MODE, key);
            //byte[] stringBytes = amalgam.getBytes("UTF8");
            byte[] raw = cipher.doFinal(data);
            //BASE64Encoder encoder = new BASE64Encoder();
            //String base64 = encoder.encode(raw);
            return raw;
        } catch (Exception e) {
            e.printStackTrace();
            throw new EncryptException("Do encrypt occurs Exception.[" + e.getMessage() + "]");
        }
    }

    /**
     * 将给定的已加密的数据通过指定的密钥进行解密
     * @param key  密钥
     * @param raw  待解密的数据
     * @return   byte[] 解密后的数据
     * @throws util.EncryptException
     */
    public static byte[] doDecrypt(Key key, byte[] raw) throws EncryptException {
        try {
            //Get a cipher object
            Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
            // Decrypt
            cipher.init(Cipher.DECRYPT_MODE, key);
            //BASE64Decoder decoder = new BASE64Decoder();
            //byte[] raw = decoder.decodeBuffer(data);
            byte[] data = cipher.doFinal(raw);
            //String result = new String(stringBytes, "UTF8");
            //System.out.println("the decrypted data is: " + result);
            return data;
        } catch (Exception e) {
            e.printStackTrace();
            throw new EncryptException("Do decrypt occurs Exception.[" + e.getMessage() + "]");
        }
    }

    /**
     * 得到一个密钥的密码
     * @param key 密钥
     * @param cipherMode 密码的类型
     * @return  Cipher
     * @throws util.EncryptException 当加密出现异常情况时,产生异常信息
     */
    public static Cipher getCipher(Key key, int cipherMode) throws EncryptException {
        try {
            Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
            cipher.init(cipherMode, key);
            return cipher;
        } catch (Exception e) {
            e.printStackTrace();
            throw new EncryptException("Generate Cipher occurs Exception.[" + e.getMessage() + "]");
        }
    }

    public static void main(String[] args) throws Exception {
        Key key = DESEncryptUtil.getKey();
        File file = new File("test.html");//随便找个文件发在当前运行目录下
        FileInputStream in = new FileInputStream(file);
        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        byte[] tmpbuf = new byte[1024];
        int count = 0;
        while ((count = in.read(tmpbuf)) != -1) {
            bout.write(tmpbuf, 0, count);
            tmpbuf = new byte[1024];
        }
        in.close();
        byte[] orgData = bout.toByteArray();
        byte[] raw = DESEncryptUtil.doEncrypt(key,orgData);

        file = new File("encrypt_result.dat");
        OutputStream out = new FileOutputStream(file);
        out.write(raw);
        out.close();

        byte[] data = DESEncryptUtil.doDecrypt(key, raw);
        file = new File("decrypt_result.html");
        out = new FileOutputStream(file);
        out.write(data);
        out.flush();
        out.close();
    }
}