为了好玩，我一直在尝试制作一个文件加密器，它对128位密钥进行按位xor加密。它似乎适用于使用某些编辑器的纯文本文件，但对于其他和更复杂的文件，我遇到“损坏的文件”错误。如果我对文本文件进行两次加密，在Gedit中它会显示原始文件的内容，但在记事本中，我只是得到了一大堆问号。
我用Java编写了这段代码，但加密部分非常普遍。密钥的形式为8个16位字符：
char[] key = {26372, 15219, 53931, 50406, 26072, 23469, 25002, 37812};
要加密文件，我有一个运行此代码的循环：
builder.append((char)(bR.read() ^ key[pos++]));
if(pos == 8) pos = 0; //returns to first position in key
这将使用BufferedReader从文件中读取下一个字符，将其与键中的下一个字符进行xors并将其附加到StringBuilder。
以下是整个代码：
import java.awt.BorderLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
public class Encryptor implements Runnable {
/**
* @param args
*/
public static void main(String[] args) {
try {
SwingUtilities.invokeAndWait(new Encryptor());
} catch(Exception e) {
e.printStackTrace();
}
}
JFrame frame;
JButton bCancel, bEncrypt;
JTextArea statusArea;
JScrollPane statusScroll;
JProgressBar progressBar;
String fileContents, fileType, fileName;
EncryptSwingWorker encryptWorker;
char[] key = {
26372, 15219, 53931, 50406, 26072, 23469, 25002, 37812};
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch(Exception e) {}
frame = new JFrame();
statusArea = new JTextArea();
statusArea.setEditable(false);
statusScroll = new JScrollPane(statusArea);
progressBar = new JProgressBar();
progressBar.setValue(0);
bCancel = new JButton("Cancel");
bCancel.setEnabled(false);
bCancel.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
int option = JOptionPane.showOptionDialog(frame,
"Are you sure you want to cancel?",
"Warning", JOptionPane.YES_NO_OPTION,
JOptionPane.QUESTION_MESSAGE, null,
null, null
);
if(option == 0) {
encryptWorker.cancel(true);
statusArea.append("Encryption cancelled\n");
progressBar.setValue(0);
progressBar.setIndeterminate(false);
bCancel.setEnabled(false);
bEncrypt.setEnabled(true);
}
}
});
bEncrypt = new JButton("Encrypt file...");
bEncrypt.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
encryptWorker = Encryptor.this.new EncryptSwingWorker();
encryptWorker.execute();
}
});
JPanel top = new JPanel(new BorderLayout());
top.add(bEncrypt, BorderLayout.CENTER);
top.add(bCancel, BorderLayout.EAST);
frame.getContentPane().add(top, BorderLayout.NORTH);
frame.getContentPane().add(statusScroll, BorderLayout.CENTER);
frame.getContentPane().add(progressBar, BorderLayout.SOUTH);
frame.setSize(200, 150);
frame.setResizable(false);
frame.setTitle("sEncryptor");
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setIconImage(Toolkit.getDefaultToolkit().getImage("encryptor.png"));
}
void encrypt() throws IOException {
JFileChooser fc = new JFileChooser();
int returnVal = fc.showOpenDialog(frame);
if(returnVal == JFileChooser.APPROVE_OPTION) {
if(fc.getSelectedFile() == null) {
JOptionPane.showOptionDialog(frame,
"You did not select a file",
"File Open Error",
JOptionPane.DEFAULT_OPTION,
JOptionPane.WARNING_MESSAGE, null,
null, null
);
encrypt();
return;
}
bCancel.setEnabled(true);
bEncrypt.setEnabled(false);
fileName = fc.getSelectedFile().getPath();
statusArea.append("Calculating size...\n");
progressBar.setIndeterminate(true);
int size = (int)(new File(fileName).length() / 32);
progressBar.setIndeterminate(false);
progressBar.setMaximum(size);
BufferedReader bR = new BufferedReader(new FileReader(fc.getSelectedFile()));
StringBuilder builder = new StringBuilder();
statusArea.append("Encrypting...\n");
int pos = 0;
for(double d = 0; bR.ready(); d += 0.03125) {
if(encryptWorker.isCancelled()) return;
progressBar.setValue((int)d);
builder.append((char)(bR.read() ^ key[pos++]));
if(pos == 8) pos = 0;
}
progressBar.setValue(0);
progressBar.setIndeterminate(true);
fileContents = builder.toString();
bR.close();
statusArea.append("Encryption finished\n");
progressBar.setIndeterminate(false);
}
}
void save(String file) throws IOException {
statusArea.append("Saving...\n");
progressBar.setIndeterminate(true);
BufferedWriter bW = new BufferedWriter(new FileWriter(file));
bW.write(fileContents);
bW.close();
progressBar.setIndeterminate(false);
statusArea.append("Done!\n");
}
void saveAs() throws IOException {
JFileChooser fc = new JFileChooser();
int returnVal = fc.showSaveDialog(frame);
if(returnVal == JFileChooser.APPROVE_OPTION) {
if(fc.getSelectedFile() == null) {
JOptionPane.showOptionDialog(frame,
"You did not select a file",
"File Open Error",
JOptionPane.DEFAULT_OPTION,
JOptionPane.WARNING_MESSAGE, null,
null, null
);
saveAs();
return;
}
save(fc.getSelectedFile().getPath());
}
}
class EncryptSwingWorker extends SwingWorker<Void, Void> {
@Override
protected Void doInBackground() throws Exception {
encrypt();
if(EncryptSwingWorker.this.isCancelled()) return null;
bCancel.setEnabled(false);
while(true) {
Object[] options = {"Override", "Save As...", "Cancel"};
int option = JOptionPane.showOptionDialog(frame,
"Override existing file?",
"Save", JOptionPane.YES_NO_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE, null,
options, options[0]
);
if(option == 0)
try {
save(fileName);
} catch(IOException e1) {
e1.printStackTrace();
}
else if(option == 1)
try {
saveAs();
} catch(IOException e1) {
e1.printStackTrace();
}
else {
int option1 = JOptionPane.showOptionDialog(frame,
"The encryption will be lost if you continue\n" +
"Are you sure you want to cancel?",
"Warning", JOptionPane.YES_NO_OPTION,
JOptionPane.QUESTION_MESSAGE, null,
null, null
);
if(option1 == 1) continue;
break;
}
break;
}
fileContents = "";
bEncrypt.setEnabled(true);
return null;
}
}
}
我的代码中是否缺少某些内容，或者整个文件的xored是否会导致问题？
答案 0 :(得分：3)
知道了。问题在于文件编码，一如既往:)。从不永远，取决于默认编码 - 它最终会适得其反。
由于Reader和Writer类是针对纯文本输入/输出的，因此它会搞砸。在这种情况下，Writer不知道如何处理它获得的各种整数并最终失败。修复Writer后，您还必须修复Reader，因为加密数据可能不仅仅是有效字符...
最佳解决方案是忽略字符，使用字节和FileInputStream，FileOutputStream（必要时由Buffered兄弟包裹），因为这些是处理二进制数据。这样，您最终会完全读/写您想要读/写的数据。试着自己一起破解它，这是一个很好的教训。如果你遇到困难，请查看here。
最简单解决方案是只更改两行。请注意，它将再次仅适用于文本文件！说真的，不要把随机数字和可打印的字符混在一起。
BufferedReader bR = new BufferedReader(new FileReader(fc.getSelectedFile()));
到
BufferedReader bR = new BufferedReader(new InputStreamReader(new FileInputStream(fc.getSelectedFile()), "UTF-8"));
和
BufferedWriter bW = new BufferedWriter(new FileWriter(file));
到
BufferedWriter bW = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "UTF-8"));