encipherdecipher.java

java编的文件加密解密程序

// EncipherDecipher.java
// Displays a frame that allows users to specify
// a password and a file name. Contents written
// to an Editor Pane can be encrypted and written
// to a file, or encrypted contents can be read from
// a file and decrypted
package com.deitel.advjhtp1.security.jce;

// Java core package
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import java.security.*;
import java.security.spec.*;

// third-party packages
import com.sun.crypto.provider.SunJCE;

// Java extension package
import javax.swing.*;
import javax.crypto.*;
import javax.crypto.spec.*;

public class EncipherDecipher extends JFrame {

   // salt for password-based encryption-decryption algorithm
   private static final byte[] salt = {
      ( byte )0xf5, ( byte )0x33, ( byte )0x01, ( byte )0x2a,
      ( byte )0xb2, ( byte )0xcc, ( byte )0xe4, ( byte )0x7f
   };
    
   // iteration count
   private int iterationCount = 100;

   // user input components.
   private JTextField passwordTextField;
   private JTextField fileNameTextField;
   private JEditorPane fileContentsEditorPane;
    
   // frame constructor
   public EncipherDecipher() {

      // set security provider
      Security.addProvider( new SunJCE() );

      // initialize main frame
      setSize( new Dimension( 400, 400 ) );
      setTitle( "Encryption and Decryption Example" );
      
      // construct top panel
      JPanel topPanel = new JPanel();     
      topPanel.setBorder( BorderFactory.createLineBorder( 
         Color.black ) );
      topPanel.setLayout( new BorderLayout() );      

      // panel where password and file name labels will be placed
      JPanel labelsPanel = new JPanel();
      labelsPanel.setLayout( new GridLayout( 2, 1 ) );
      JLabel passwordLabel = new JLabel( " Password: " );
      JLabel fileNameLabel = new JLabel( " File Name: " );
      labelsPanel.add( fileNameLabel );
      labelsPanel.add( passwordLabel );
      topPanel.add( labelsPanel, BorderLayout.WEST );

      // panel where password and file name textfields will be placed
      JPanel textFieldsPanel = new JPanel();
      textFieldsPanel.setLayout( new GridLayout( 2, 1 ) );
      passwordTextField = new JPasswordField();
      fileNameTextField = new JTextField();
      textFieldsPanel.add( fileNameTextField );
      textFieldsPanel.add( passwordTextField );
      topPanel.add( textFieldsPanel, BorderLayout.CENTER );
     
      // construct middle panel
      JPanel middlePanel = new JPanel();
      middlePanel.setLayout( new BorderLayout() );

      // construct and place title label for contents pane
      JLabel fileContentsLabel = new JLabel();
      fileContentsLabel.setText( " File Contents" );
      middlePanel.add( fileContentsLabel, BorderLayout.NORTH );
      
      // initialize and place editor pane within scroll panel
      fileContentsEditorPane = new JEditorPane();
      middlePanel.add(  
         new JScrollPane( fileContentsEditorPane ),
                          BorderLayout.CENTER );
      
      // construct bottom panel
      JPanel bottomPanel = new JPanel();
      
      // create encrypt button
      JButton encryptButton = 
         new JButton( "Encrypt and Write to File" );
      encryptButton.addActionListener( 
      
         new ActionListener() {
            
            public void actionPerformed( ActionEvent event ) 
            {
               encryptAndWriteToFile();
            }
         }
      );
      bottomPanel.add( encryptButton );

      // create decrypt button
      JButton decryptButton = 
         new JButton( "Read from File and Decrypt" );
      decryptButton.addActionListener( 
      
         new ActionListener() {
      
            public void actionPerformed( ActionEvent event ) 
            {
               readFromFileAndDecrypt();
            }
         }
      );
      bottomPanel.add( decryptButton );

      // initialize main frame window
      JPanel contentPane = ( JPanel ) this.getContentPane();
      contentPane.setLayout( new BorderLayout() );
      contentPane.add( topPanel, BorderLayout.NORTH );
      contentPane.add( middlePanel, BorderLayout.CENTER );
      contentPane.add( bottomPanel, BorderLayout.SOUTH );
      
   } // end constructor
   
   // obtain contents from editor pane and encrypt
   private void encryptAndWriteToFile() 
   {
   
      // obtain user input
      String originalText = fileContentsEditorPane.getText();
      String password = passwordTextField.getText();
      String fileName = fileNameTextField.getText();

      // create secret key and get cipher instance
      Cipher cipher = null;
      
      try {
          
         // create password based encryption key object
         PBEKeySpec keySpec = 
            new PBEKeySpec( password.toCharArray() );
                  
         // obtain instance for secret key factory
         SecretKeyFactory keyFactory = 
            SecretKeyFactory.getInstance( "PBEWithMD5AndDES" );
         
         // generate secret key for encryption
         SecretKey secretKey = keyFactory.generateSecret( keySpec );

         // specifies parameters used with password based encryption
         PBEParameterSpec parameterSpec = 
            new PBEParameterSpec( salt, iterationCount );
         
         // obtain cipher instance reference
         cipher = Cipher.getInstance( "PBEWithMD5AndDES" );
   
         // initialize cipher in encrypt mode
         cipher.init( Cipher.ENCRYPT_MODE, secretKey, 
            parameterSpec );
      } 
      
      // handle NoSuchAlgorithmException 
      catch ( NoSuchAlgorithmException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // handle InvalidKeySpecException 
      catch ( InvalidKeySpecException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // handle InvalidKeyException 
      catch ( InvalidKeyException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // handle NoSuchPaddingException 
      catch ( NoSuchPaddingException exception ) {
         exception.printStackTrace();
         System.exit( 1 );          
      }
      
      // handle InvalidAlgorithmParameterException 
      catch ( InvalidAlgorithmParameterException exception ) {
         exception.printStackTrace();
         System.exit( 1 );          
      }
     
      // create array of bytes
      byte[] outputArray = null;

      try {
         outputArray = originalText.getBytes( "ISO-8859-1" );
      } 
      
      // handle UnsupportedEncodingException
      catch ( UnsupportedEncodingException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // create FileOutputStream
      File file = new File( fileName );
      FileOutputStream fileOutputStream = null;
      
      try {
         fileOutputStream = new FileOutputStream( file );
      } 
      
      // handle IOException
      catch ( IOException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // create CipherOutputStream
      CipherOutputStream out = 
         new CipherOutputStream( fileOutputStream, cipher );
      
      // write contents to file and close
      try {
         out.write( outputArray );
         out.flush();
         out.close();
      } 
      
      // handle IOException 
      catch ( IOException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
         
      // contain bytes read from file
      Vector fileBytes = new Vector();

      // read contents from file to show user encrypted text
      try {
         FileInputStream in = new FileInputStream( file );
            
         // read bytes from stream.
         byte contents;
         
         while ( in.available() > 0 ) {
            contents = ( byte )in.read();
            fileBytes.add( new Byte( contents ) );
         }
           
         in.close();
      } 
      
      // handle IOException
      catch ( IOException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // create byte array from contents in Vector fileBytes
      byte[] encryptedText = new byte[ fileBytes.size() ];
      
      for ( int i = 0; i < fileBytes.size(); i++ ) {
         encryptedText[ i ] = 
            ( ( Byte ) fileBytes.elementAt( i ) ).byteValue();
      }
      
      // update Editor Pane contents
      fileContentsEditorPane.setText( new String( encryptedText ) );      
   }

   // obtain contents from file and decrypt
   private void readFromFileAndDecrypt() 
   {

      // used to rebuild byte list
      Vector fileBytes = new Vector();
          
      // obtain user input
      String password = passwordTextField.getText();
      String fileName = fileNameTextField.getText();

      // create secret key
      Cipher cipher = null;
      
      try {
         // create password based encryption key object
         PBEKeySpec keySpec = 
            new PBEKeySpec( password.toCharArray() );
                  
         // obtain instance for secret key factory
         SecretKeyFactory keyFactory = 
            SecretKeyFactory.getInstance( "PBEWithMD5AndDES" );
         
         // generate secret key for encryption
         SecretKey secretKey = keyFactory.generateSecret( keySpec );

         // specifies parameters used with password based encryption
         PBEParameterSpec parameterSpec = 
            new PBEParameterSpec( salt, iterationCount );         
         
         // obtain cipher instance reference.
         cipher = Cipher.getInstance( "PBEWithMD5AndDES" );
   
         // initialize cipher in decrypt mode
         cipher.init( Cipher.DECRYPT_MODE, secretKey, 
            parameterSpec );
      }
      
      // handle NoSuchAlgorithmException 
      catch ( NoSuchAlgorithmException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // handle InvalidKeySpecException 
      catch ( InvalidKeySpecException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // handle InvalidKeyException 
      catch ( InvalidKeyException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }

      // handle NoSuchPaddingException 
      catch ( NoSuchPaddingException exception ) {
         exception.printStackTrace();
         System.exit( 1 );          
      }
      
      // handle InvalidAlgorithmParameterException 
      catch ( InvalidAlgorithmParameterException exception ) {
         exception.printStackTrace();
         System.exit( 1 );          
      }

         
      // read and decrypt contents from file
      try {
         File file = new File( fileName );
         FileInputStream fileInputStream = 
            new FileInputStream( file );
         
         CipherInputStream in = 
            new CipherInputStream( fileInputStream, cipher );
         
         // read bytes from stream.
         byte contents = ( byte ) in.read();
         
         while ( contents != -1 ) {   
            fileBytes.add( new Byte( contents ) );
            contents = ( byte ) in.read();
         }           
         in.close();
      
      } 
      
      // handle IOException
      catch ( IOException exception ) {
         exception.printStackTrace();
         System.exit( 1 );
      }
      
      // create byte array from contents in Vector fileBytes
      byte[] decryptedText = new byte[ fileBytes.size() ];
      
      for ( int i = 0; i < fileBytes.size(); i++ ) {
         decryptedText[ i ] = 
            ( ( Byte )fileBytes.elementAt( i ) ).byteValue();
      }
                
      // update Editor Pane contents.
      fileContentsEditorPane.setText( new String( decryptedText ) );
   }
   
   // create frame and display
   public static void main( String[] args ) 
   {
      EncipherDecipher crypto = 
         new EncipherDecipher();
      crypto.validate();
      crypto.setVisible( true );       
   }
}

/***************************************************************
 * (C) Copyright 2002 by Deitel & Associates, Inc. and         *
 * Prentice Hall. All Rights Reserved.                         *
 *                                                             *
 * DISCLAIMER: The authors and publisher of this book have     *
 * used their best efforts in preparing the book. These        *
 * efforts include the development, research, and testing of   *
 * the theories and programs to determine their effectiveness. *
 * The authors and publisher make no warranty of any kind,     *
 * expressed or implied, with regard to these programs or to   *
 * the documentation contained in these books. The authors     *
 * and publisher shall not be liable in any event for          *
 * incidental or consequential damages in connection with, or  *
 * arising out of, the furnishing, performance, or use of      *
 * these programs.                                             *
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