Question

我是Java的新手，我试图创建一个vigenere密码。这是凯撒的一种转变，只有一个字母不止一个字，而且它重复了，所以密码会更难破解。我只完成了程序的加密部分，但是当我意识到它运行不正常时我停了下来。我的意思是，它在某种程度上是有效的，我认为，当我输入更长的字符串时，程序决定对我失败。它告诉我

主题“主要”

中的例外情况

java.lang.ArrayIndexOutOfBoundsException: 26
at Cipher.encrypt(Cipher.java:30)
at Cipher.main(Cipher.java:51)

嗯，我知道有一些“标准”方法可以在Java上创建vigenere密码，但我还没有学到一些他们正在使用的东西，所以我想知道你发现这个程序有什么问题。非常感谢！！！

import java.util.Scanner;


public class Cipher 
{

public static void encrypt (char[]alpha,String p, String key)

{
String cipher=("");


for (int i=0; i<p.length(); i++)


{ 


char c = p.charAt(i);


 int j=-1;


 int k=i%key.length();


 int l=-1;

        do // this one finds the letter character c corresponds to in the alphabet
        {
            j=j+1;
        }while(c!=alpha[j]);

        do// this one finds the letter that the key (or the letter used in the key) corresponds to in the alphabet
        {
            l=l+1;
        }while(key.charAt(k)!=alpha[l]);

         if (j+l>26)//if, say, the key is z and the character is z, then they would minus the shift by 26 so it stays inside the alphabet
        {
            c=alpha[j+l-26];
        }
        else
        {
            c=alpha[j+l];
        }

            cipher=cipher+c;
        }
        System.out.println(cipher.toUpperCase());
}
public static void main(String[] args) 
{
    char[] alpha = "abcdefghijklmnopqrstuvwxyz".toCharArray();
    Scanner scan = new Scanner(System.in);  
    System.out.println("Please enter a key for your vigenere cipher");
    String key= scan.nextLine().toLowerCase().replaceAll("[\\W]", "");
    System.out.println("Your key is "+key.toUpperCase());
    System.out.println("Would you like to encrypt or decrypt a message?");
    String ans=scan.nextLine();
    if (ans.equalsIgnoreCase("encrypt"))
    {
    System.out.println("Please enter your plaintext");
    String p= scan.nextLine().toLowerCase().replaceAll("[\\W]", "");
    System.out.println("Your plaintext is "+p);
    encrypt(alpha,p,key);
    }
    else
    {
    }
    }

}

}

Answer 1

这是我放在一起的Vigenere密码。

我使用了GUI，但您可以将TranslateTextListener类的密码和解密方法与控制台输入和输出一起使用。

以下是代码：

package com.ggl.testing;

import java.awt.Component;
import java.awt.Container;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class VigenèreCipher implements Runnable {

    private static final Insets normalInsets = new Insets(10, 10, 0, 10);
    private static final Insets finalInsets = new Insets(10, 10, 10, 10);

    private JTextArea originalTextArea;
    private JTextArea keyTextArea;
    private JTextArea cipherTextArea;
    private JTextArea uncipheredTextArea;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new VigenèreCipher());
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("Vigenère Cipher");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(createCipherPanel());

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel createCipherPanel() {
        JPanel panel = new JPanel();
        panel.setLayout(new GridBagLayout());

        int gridy = 0;

        JLabel originalTextLabel = new JLabel("Original Text:");
        addComponent(panel, originalTextLabel, 0, gridy, 1, 1, normalInsets,
                GridBagConstraints.LINE_START, GridBagConstraints.HORIZONTAL);

        originalTextArea = new JTextArea(5, 30);
        originalTextArea.setLineWrap(true);
        originalTextArea.setWrapStyleWord(true);
        JScrollPane originalTextScrollPane = new JScrollPane(originalTextArea);
        addComponent(panel, originalTextScrollPane, 1, gridy++, 1, 1,
                normalInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        JLabel keyTextLabel = new JLabel("Key Text:");
        addComponent(panel, keyTextLabel, 0, gridy, 1, 1, normalInsets,
                GridBagConstraints.LINE_START, GridBagConstraints.HORIZONTAL);

        keyTextArea = new JTextArea(5, 30);
        keyTextArea.setLineWrap(true);
        keyTextArea.setWrapStyleWord(true);
        JScrollPane keyTextScrollPane = new JScrollPane(keyTextArea);
        addComponent(panel, keyTextScrollPane, 1, gridy++, 1, 1, normalInsets,
                GridBagConstraints.LINE_START, GridBagConstraints.HORIZONTAL);

        JLabel cipherTextLabel = new JLabel("Cipher Text:");
        addComponent(panel, cipherTextLabel, 0, gridy, 1, 1, finalInsets,
                GridBagConstraints.LINE_START, GridBagConstraints.HORIZONTAL);

        cipherTextArea = new JTextArea(5, 30);
        cipherTextArea.setLineWrap(true);
        JScrollPane cipherTextScrollPane = new JScrollPane(cipherTextArea);
        addComponent(panel, cipherTextScrollPane, 1, gridy++, 1, 1,
                finalInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        JLabel uncipheredTextLabel = new JLabel("Unciphered Text:");
        addComponent(panel, uncipheredTextLabel, 0, gridy, 1, 1, finalInsets,
                GridBagConstraints.LINE_START, GridBagConstraints.HORIZONTAL);

        uncipheredTextArea = new JTextArea(5, 30);
        uncipheredTextArea.setLineWrap(true);
        uncipheredTextArea.setWrapStyleWord(true);
        JScrollPane uncipheredTextScrollPane = new JScrollPane(
                uncipheredTextArea);
        addComponent(panel, uncipheredTextScrollPane, 1, gridy++, 1, 1,
                finalInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        JButton submitButton = new JButton("Translate text");
        submitButton.addActionListener(new TranslateTextListener());
        addComponent(panel, submitButton, 0, gridy++, 2, 1, finalInsets,
                GridBagConstraints.CENTER, GridBagConstraints.NONE);

        return panel;
    }

    private void addComponent(Container container, Component component,
            int gridx, int gridy, int gridwidth, int gridheight, Insets insets,
            int anchor, int fill) {
        GridBagConstraints gbc = new GridBagConstraints(gridx, gridy,
                gridwidth, gridheight, 1.0D, 1.0D, anchor, fill, insets, 0, 0);
        container.add(component, gbc);
    }

    public class TranslateTextListener implements ActionListener {

        private char[] cipherAlphabet;

        private int lowerLimit;
        private int upperLimit;

        public TranslateTextListener() {
            this.lowerLimit = 32;
            this.upperLimit = 126;
            this.cipherAlphabet = new char[upperLimit - lowerLimit + 1];
            // Grab all the ASCII characters between space and ~, inclusive
            for (int i = lowerLimit; i <= upperLimit; i++) {
                cipherAlphabet[i - lowerLimit] = (char) i;
            }
        }

        @Override
        public void actionPerformed(ActionEvent event) {
            String text = originalTextArea.getText().trim();
            String key = keyTextArea.getText().trim();
            String cipher = cipherTextArea.getText().trim();
            String uncipher = "";

            if (!text.equals("") && !key.equals("")) {
                cipher = cipher(text, key);
            }

            if (!key.equals("") && !cipher.equals("")) {
                uncipher = uncipher(cipher, key);
            }

            cipherTextArea.setText(cipher);
            uncipheredTextArea.setText(uncipher);
        }

        private String cipher(String text, String key) {
            StringBuilder builder = new StringBuilder(text.length());
            int keyIndex = 0;
            for (int i = 0; i < text.length(); i++) {
                char c = text.charAt(i);
                int pos = (int) c;
                if (pos < lowerLimit || pos > upperLimit) {
                    builder.append(c);
                } else {
                    char k = key.charAt(keyIndex);
                    pos = getCharacterPosition(c);
                    int pos2 = getCharacterPosition(k);
                    int sum = (pos + pos2) % cipherAlphabet.length;
                    builder.append(getCharacter(sum));
                    keyIndex = ++keyIndex % key.length();
                }
            }
            return builder.toString();
        }

        private String uncipher(String cipher, String key) {
            StringBuilder builder = new StringBuilder(cipher.length());
            int keyIndex = 0;
            for (int i = 0; i < cipher.length(); i++) {
                char c = cipher.charAt(i);
                int pos = (int) c;
                if (pos < lowerLimit || pos > upperLimit) {
                    builder.append(c);
                } else {
                    char k = key.charAt(keyIndex);
                    pos = getCharacterPosition(c);
                    int pos2 = getCharacterPosition(k);
                    int sum = pos - pos2;
                    while (sum < 0) {
                        sum += cipherAlphabet.length;
                    }
                    sum = sum % cipherAlphabet.length;
                    builder.append(getCharacter(sum));
                    keyIndex = ++keyIndex % key.length();
                }
            }
            return builder.toString();
        }

        private int getCharacterPosition(char c) {
            for (int i = 0; i < cipherAlphabet.length; i++) {
                if (c == cipherAlphabet[i]) {
                    return i;
                }
            }

            return -1;
        }

        private char getCharacter(int index) {
            if (index >= 0 && index < cipherAlphabet.length) {
                return cipherAlphabet[index];
            } else {
                return '?';
            }
        }

    }
}

Answer 2

尝试不同的方法？这是我的，它只是创建一个新的变量，它将保存加密的消息，并根据ASCII值存储更改的字符。我仍然需要添加空格，到目前为止它只加密没有任何空格的消息，但它可以是我想要的。

public class vigenere {
public static void main(String[] args) {
    String encryptedMessage = "";
    String extended = "";
    int temp, counter;

    String plain_text = JOptionPane.showInputDialog("Enter the text you wish to encrypt: ");
    String keyword = JOptionPane.showInputDialog("Enter the keyword: ");

    counter = plain_text.length() / keyword.length() + 3;

    for (int i = 0; i < counter; i++){
        extended += keyword;
    }

    for (int j = 0; j < plain_text.length(); j++) {


            if (plain_text.charAt(j) + ((extended.charAt(j) - 97)) > 122) {
                temp = (int)(plain_text.charAt(j) + (extended.charAt(j) -123 ));
                encryptedMessage += (char)temp;
            } else {
                temp = (int)(plain_text.charAt(j) + (extended.charAt(j) - 97 ));
                encryptedMessage += (char)temp;
            }
        }
    }
    JOptionPane.showMessageDialog(null, encryptedMessage);
}

}

＆＃34;计数器＆＃34;是多少次我们必须延长关键字以匹配明文的长度，我把+3放在最后确定但我认为+1就足够了。另外，我对此非常陌生，因此这段代码基本可以得到xD

Answer 3

alpha中有26个字符，因此有效索引为0-25。

您检查是否j+l > 26，并根据需要进行转移，但您应该检查是否j+l > 25。

更好的是，不要使用if进行测试并处理不同的情况，只需无条件地执行此操作：

c = alpha[(j + l) % 26];

此外，不是在字母表中搜索字符，而是使用减法：

j = c - 'a';

我将这些全部放在一起：

static String encrypt(String message, String key) {
  StringBuilder buf = new StringBuilder(message.length());
  for (int idx = 0; idx < message.length(); ++idx) {
    char p = message.charAt(idx);
    int j = p - 'a';
    char k = key.charAt(i % key.length());
    int l = k - 'a';
    char c = (char) ('a' + ((j + l) % 26));
    buf.append(c);
  }
  return buf.toString();
}

Vigenere Cipher（Java）

3 个答案: