用Java的加密机制来保护你的数据

<script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"> </script> Java开发工具包 (JDK)对加密和安全性有很好的支持。其中一个优势就是其内置的对Socket通信的支持。因此，很容易做到在服务器和客户之间建立安全的数据流。 流 Java streams 是一个强大的编程工具。java.io包提供了很多标准的流类型，并能很容易的建立自己的流类型。流的一个有用的特点是和链表一样的简单处理过程。表 A是一个用链表读取文本的例子。 ufferedReader br = new BufferedReader( new FileReader(“c:/foo.txt”)); String line = null; while((line = br.readLine()) != null) { System.out.println(line); } 这段代码将 FileReader和 BufferedReader链接起来。我们在用客户机/服务器应用程序的时候也会用到类似的概念。 关键字 对于验证来说，关键字很重要，表 B (KeyGen.java)提供了一个称为 getSecretKey的标准方法。通过运行KeyGen来产生一个关键字。因为我们采用同步方法，所以客户机和服务器必须用相同的关键字。 isting B?KeyGen.java /* * Created by IntelliJ IDEA. * User: jbirchfield * Date: Mar 19, 2002 * Time: 9:33:22 AM */ import com.sun.crypto.provider.SunJCE; import javax.crypto.KeyGenerator; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.security.Key; import java.security.NoSuchAlgorithmException; import java.security.Security; public class KeyGen { public static final String KEY_FILE = "secret.key"; public static final String ALGORITHM = "DES"; public static void main(String[] args) { Security.addProvider(new SunJCE()); new KeyGen(); } public KeyGen() { KeyGenerator kg = null; try { kg = KeyGenerator.getInstance(ALGORITHM); Key key = kg.generateKey(); writeKey(KEY_FILE, key); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } } private void writeKey(String filename, Object o) { try { FileOutputStream fos = new FileOutputStream(filename); ObjectOutputStream oos = new ObjectOutputStream(fos); oos.writeObject(o); oos.flush(); fos.close(); } catch (IOException e) { e.printStackTrace(); } } public static Key getSecretKey() { Security.addProvider(new SunJCE()); FileInputStream fis = null; try { fis = new FileInputStream(KEY_FILE); } catch (FileNotFoundException e) { e.printStackTrace(); } Key key = null; try { ObjectInputStream ois = null; ois = new ObjectInputStream(fis); key = null; key = (Key) ois.readObject(); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } System.out.println("key = " key); return key; } } 安全socket 我们从一个简单的类开始，它提供我们在普通socket对象之上的加密。表 C (SecretSocket.java) 包含了两段代码－Socket和Key对象。我们的构造器创建了变量并初始化了密码： outCipher = Cipher.getInstance(algorithm); outCipher.init(Cipher.ENCRYPT_MODE, key); inCipher = Cipher.getInstance(algorithm); inCipher.init(Cipher.DECRYPT_MODE, key); isting C?SecretSocket.java /* * Created by IntelliJ IDEA. * User: jbirchfield * Date: Mar 20, 2002 * Time: 9:07:51 AM */ import org.bouncycastle.jce.provider.BouncyCastleProvider; import javax.crypto.Cipher; import javax.crypto.CipherInputStream; import javax.crypto.CipherOutputStream; import javax.crypto.KeyGenerator; import javax.crypto.NoSuchPaddingException; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.Socket; import java.net.UnknownHostException; import java.security.InvalidKeyException; import java.security.Key; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.Security; public class SecretSocket { private Key key = null; private Cipher outCipher = null; private Cipher inCipher = null; private CipherInputStream cis = null; private CipherOutputStream cos = null; private Socket socket = null; private String algorithm = "DES"; public SecretSocket(Socket socket, Key key) { this.socket = socket; this.key = key; algorithm = key.getAlgorithm(); initializeCipher(); } private void initializeCipher() { try { outCipher = Cipher.getInstance(algorithm); outCipher.init(Cipher.ENCRYPT_MODE, key); inCipher = Cipher.getInstance(algorithm); inCipher.init(Cipher.DECRYPT_MODE, key); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (NoSuchPaddingException e) { e.printStackTrace(); } catch (InvalidKeyException e) { e.printStackTrace(); } } public InputStream getInputStream() throws IOException { InputStream is = socket.getInputStream(); cis = new CipherInputStream(is, inCipher); return cis; } public OutputStream getOutputStream() throws IOException { OutputStream os = socket.getOutputStream(); cos = new CipherOutputStream(os, outCipher); return cos; } } 因为socket是双向的通信，所以我们采用两个密码。加密输出的数据并解密输入的数据。我们使用getInputStream()和 getOutputStream(),这两种方法来加密合解密通用的输入和输出的经过包装的数据流。见 表 D 。 isting D public InputStream getInputStream() throws IOException { InputStream is = socket.getInputStream(); cis = new CipherInputStream(is, inCipher); return cis; } public OutputStream getOutputStream() throws IOException { OutputStream os = socket.getOutputStream(); cos = new CipherOutputStream(os, outCipher); return cos; } 在JCE的javax.crypto包中包含CipherInputStream和 CipherOutputStream这两种流类型。他们接收输入输出的流对象和密码对象。 Socket 服务器 开始写我们的socket服务器类吧。 表 E (SecretSocketServer.java)是一个完整的列表。SecretSocketServer在一个端口打开ServerSocket，当接收到连接时，使用SocketHandler产生一个线程来操作连接。 isting E?SecretSocketServer.java /* * Created by IntelliJ IDEA. * User: jbirchfield * Date: Mar 20, 2002 * Time: 9:32:17 AM */ import java.net.ServerSocket; import java.net.Socket; import java.io.IOException; public class SecretSocketServer { public static void main(String[] args) { new SecretSocketServer(); } public SecretSocketServer() { ServerSocket ss = null; try { ss = new ServerSocket(4444); } catch (IOException e) { e.printStackTrace(); } while(true) { try { System.out.println("Waiting..."); Socket s = ss.accept(); SocketHandler h = new SocketHandler(s); Thread t = new Thread(h); t.start(); } catch (IOException e) { e.printStackTrace(); } } } } Socket 句柄 表 F (SocketHandler.java) 确定一个socket对象，通过KeyGen来定位关键字，并建立一个 SecretSocket 对象。. Key key = KeyGen.getSecretKey(); this.ss = new SecretSocket(s, key); isting F?SocketHandler.java /* * Created by IntelliJ IDEA. * User: jbirchfield * Date: Mar 20, 2002 * Time: 9:34:22 AM */ import java.io.IOException; import java.io.InputStream; import java.net.Socket; import java.security.Key; public class SocketHandler implements Runnable { private Socket s = null; private SecretSocket ss = null; private InputStream in = null; public SocketHandler(Socket s) { this.s = s; Key key = KeyGen.getSecretKey(); this.ss = new SecretSocket(s, key); try { in = ss.getInputStream(); } catch (IOException e) { e.printStackTrace(); } } public void run() { boolean bool = true; while (bool) { bool = listen(); } try { s.close(); } catch (IOException e) { e.printStackTrace(); } } public boolean listen() { int aByte; try { while ((aByte = in.read()) >= 0) { System.out.println((char)aByte); } } catch (IOException e) { System.out.println("returning false..."); } return false; } } 注意表F中的 ss对SocketHandler来说是一个实变量。所有的socket 处理都是通过SecretSocket而不是Socket对象。然后我们使用下面的代码： in = ss.getInputStream(); 记住，在SecretSocket中，getInputStream是和CipherInputStream以及 InputStream相结合的。因为SocketHandler 是一个可执行的界面，我们为它生成一个 run()方法。这个方法只是在等待socket的数据： boolean bool = true; while (bool) { bool = listen(); } listen方法用来监听socket 。 int aByte; while ((aByte = in.read()) >= 0) { system.out.println((char)aByte); } Socket 客户 现在我们来看看客户端。见 表 G 。客户端的工作和服务器端很相似，只是反过来了。首先，我们创立一个套接字连接到服务器。使用KeyGen 找到关键字，创立一个安全套接字（SecretSocket）。然后我们利用它的OutputStream给服务器发送数据： Key key = KeyGen.getSecretKey(); Socket s = new Socket("localhost", 4444); SecretSocket ss = new SecretSocket(s, key); OutputStream os = ss.getOutputStream(); os.write("Hello World!".getBytes()); os.flush(); os.close(); s.close(); 总结 通过JCE中的java流和链表，我们可以轻松的加密基于socket的网络通信。