Applet implementation to code Caesar’s substitution cipher

March 16th, 2011 | Author: Haider al-Khateeb

In cryptography, Caesar cipher is one of the simplest encryption techniques. It is a substitution cipher in which each letter in the plaintext is replaced by a letter after a fixed number of positions down the alphabet. However, this applet shifts each character (letter, number of symbol) after a number of positions down the ASCII table. Caesar’s cipher is categorised as a symmetric encryption and the secret key in this case is the number of shifts!

To encrypt, select the encode mode, number of shifts and click Run.

You may encode a message multiple times.

To Decrypt, select the decode mode and reverse your steps.

Cannot run Applet!
You do not have Java 2 JDK, Standard Edition v 1.5.0_05 support for APPLET!!

IMPORTANT NOTICE: please note that I did not sign this applet so you may not be able to copy/paste text between the applet and your computer. To read more about this issue I posted another blog called: Creating an executable jar file for an applet.
If you like this piece of software, download the applet to your computer from here (executable jar file). Running the software on your system will solve the copy/paste problem. To successfully execute jar files on your system, you -of course- need to have the Java Runtime Environment (JRE) installed. If you still can not run the jar file, use the ‘Open with’ option and select javax.exe (javax.exe is located inside the bin directory of your JRE folder e.g. C:\Program Files\Java\jre6\bin).

Further, here is the source code I developed for this applet for you to check and compile if you are interested.

/*
 * CaesarCode.java
 *
 * By Haider al-Khateeb (http://blog.creativeitp.com)
 * Created on Mar 14, 2011.
 */
 
package CaesarCodePackage;
 
import javax.swing.JOptionPane;
 
public class CaesarCode extends javax.swing.JApplet {
 
    private String inputText;
	private char [] inputTextChr;
	private int [] inputTextInt;
	private char [] outputTextChr;
	private String intArray = "";
	private String cipher = "";
	private String plain = "";
 
	public static String newLine = System.getProperty("line.separator");
 
             public void inputText(String inputText)
	{
		this.inputText = inputText;
	}
 
	public String getinputText()
	{
		return inputText;
	}
 
	public void convertToChar()
        {
		inputTextChr = inputText.toCharArray();
	}
 
	public void convertCharToInt()
        {
		inputTextInt = new int[inputTextChr.length];
		for (int i=0;i<inputTextChr.length;i++)
                    {
			int inputTextInt2 = (int) inputTextChr[i];
			inputTextInt[i] = inputTextInt2;
                    }
	}
 
 
	public String getIntArray(){
		for (int i=0;i<inputTextInt.length;i++)
                    {
			intArray += inputTextInt[i] + ", ";
                    }
		return intArray;
	}
 
	public String encrypt(int shift)
        {
		for (int i=0;i<inputTextInt.length;i++)
                        {
 
			if ((inputTextInt[i]+shift)> 126)
			{
				inputTextInt[i] =((shift-(126-inputTextInt[i]))+31);
			}
 
			else {	inputTextInt[i] += shift;
			}
 
			}
		outputTextChr = new char[inputTextInt.length];
		for (int i=0;i<outputTextChr.length;i++){
			char outputTextChr2 = (char) inputTextInt[i];
			outputTextChr[i] = outputTextChr2;
                        }
		for (int i=0;i<outputTextChr.length;i++){
			cipher += outputTextChr[i];
			}
		return cipher;
	}
 
	public String decrypt(int shift){
		for (int i=0;i<inputTextInt.length;i++)
                {
			if ((inputTextInt[i]-shift)< 32)
			{
				inputTextInt[i] =(127-(shift-(inputTextInt[i]-32)));
			}
 
			else { inputTextInt[i] -= shift; }
			}
		outputTextChr = new char[inputTextInt.length];
		for (int i=0;i<outputTextChr.length;i++){
			char outputTextChr2 = (char) inputTextInt[i];
			outputTextChr[i] = outputTextChr2;
                    }
		for (int i=0;i<outputTextChr.length;i++){
			plain += outputTextChr[i];
			}
		return plain;
	}
 
 
    /** Initializes the applet CaesarCode */
    public void init() {
        try {
            java.awt.EventQueue.invokeAndWait(new Runnable() {
                public void run() {
                    initComponents();
                }
            });
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
 
    /** This method is called from within the init() method to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
    private void initComponents() {
 
        jPanel1 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();
        jComboBox1 = new javax.swing.JComboBox();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jScrollPane2 = new javax.swing.JScrollPane();
        jList1 = new javax.swing.JList();
        jButton1 = new javax.swing.JButton();
        jButton2 = new javax.swing.JButton();
        jButton3 = new javax.swing.JButton();
        jButton4 = new javax.swing.JButton();
        jButton5 = new javax.swing.JButton();
 
        jPanel1.setBackground(new java.awt.Color(102, 204, 255));
        jPanel1.setBorder(javax.swing.BorderFactory.createEtchedBorder(new java.awt.Color(102, 255, 255), null));
 
        jLabel1.setText("Input your message in the following box");
 
        jTextArea1.setColumns(20);
        jTextArea1.setLineWrap(true);
        jTextArea1.setRows(5);
        jTextArea1.setWrapStyleWord(true);
        jScrollPane1.setViewportView(jTextArea1);
 
        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Encode", "Decode" }));
 
        jLabel2.setText("Select mode");
 
        jLabel3.setHorizontalAlignment(javax.swing.SwingConstants.RIGHT);
        jLabel3.setText("Number of shifts");
 
        jList1.setModel(new javax.swing.AbstractListModel() {
            String[] strings = { "01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "40", "41", "42", "43", "44", "45", "46", "47", "48", "49", "50" };
            public int getSize() { return strings.length; }
            public Object getElementAt(int i) { return strings[i]; }
        });
        jList1.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
        jList1.setVisibleRowCount(3);
        jScrollPane2.setViewportView(jList1);
 
        jButton1.setText("Run");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });
 
        jButton2.setText("Help?");
        jButton2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton2ActionPerformed(evt);
            }
        });
 
        jButton3.setText("Copy");
        jButton3.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton3ActionPerformed(evt);
            }
        });
 
        jButton4.setText("Paste");
        jButton4.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton4ActionPerformed(evt);
            }
        });
 
        jButton5.setText("Select All");
        jButton5.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton5ActionPerformed(evt);
            }
        });
 
        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(19, 19, 19)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addComponent(jButton2)
                        .addGap(57, 57, 57)
                        .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 58, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(29, 29, 29))
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, 348, Short.MAX_VALUE)
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                        .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(8, 8, 8))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(12, 12, 12)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                            .addGroup(jPanel1Layout.createSequentialGroup()
                                .addComponent(jButton3)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(jButton4)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(jButton5))
                            .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 278, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                                .addGap(74, 74, 74)
                                .addComponent(jLabel3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                .addGap(45, 45, 45)
                                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                    .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 71, javax.swing.GroupLayout.PREFERRED_SIZE))))
                        .addGap(58, 58, 58)))
                .addGap(27, 27, 27))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jLabel3))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jButton2)
                    .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(16, 16, 16)
                .addComponent(jLabel1)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jButton3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jButton4, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jButton5, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 188, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jButton1)
                .addContainerGap())
        );
 
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
    }// </editor-fold>//GEN-END:initComponents
 
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton1ActionPerformed
        // TODO add your handling code here:
          if (jList1.getSelectedIndex() > -1)
             {
		CaesarCode msg = new CaesarCode();
		msg.inputText(jTextArea1.getText());
		msg.convertToChar(); //convert plain text string to char data type
		msg.convertCharToInt(); // convert char to their equivalent integer (decimal number) in the ASCCI table
		//msg.getIntArray(); // show decimal numbers of the inputText
		int shift = 1 + jList1.getSelectedIndex();
			  if (jComboBox1.getSelectedItem() == "Encode")
			  {
                                jTextArea1.setText(msg.encrypt(shift));
                                //  msg.encrypt(shift) = encrypt and output cipher
			  }
			   else
			  {
				jTextArea1.setText(msg.decrypt(shift));
                                  //  msg.encrypt(shift) = decrypt and output cipher
			  }
		}
		else
                {
                    JOptionPane.showMessageDialog(null, "Please select a number of shifts first!");
		 }
    }//GEN-LAST:event_jButton1ActionPerformed
 
    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton2ActionPerformed
        // TODO add your handling code here:
        JOptionPane.showMessageDialog(null, "To encrypt, select the encode mode, the number of shifts and click ‘Run’." + newLine +
                                            "You may encode the same message multiple times." + newLine +
                                            "To Decrypt, select the decode mode and reverse your encryption steps." + newLine + newLine +
                                            "By Haider al-Khateeb (http://blog.creativeitp.com)");
    }//GEN-LAST:event_jButton2ActionPerformed
 
    private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton3ActionPerformed
        // TODO add your handling code here:
        jTextArea1.copy();
    }//GEN-LAST:event_jButton3ActionPerformed
 
    private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton4ActionPerformed
        // TODO add your handling code here:
        jTextArea1.paste();
    }//GEN-LAST:event_jButton4ActionPerformed
 
    private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton5ActionPerformed
        // TODO add your handling code here:
        jTextArea1.selectAll();
    }//GEN-LAST:event_jButton5ActionPerformed
 
 
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JButton jButton4;
    private javax.swing.JButton jButton5;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JList jList1;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JTextArea jTextArea1;
    // End of variables declaration//GEN-END:variables
 
}

Posted in Cryptography, Java |

Tags: Substitution Cipher, Symmetric Encryption

One Response to “Applet implementation to code Caesar’s substitution cipher”

DIVYA:

March 19, 2011 at 5:20 AM

super amazing ..

Reply

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Applet implementation to code Caesar’s substitution cipher

One Response to “Applet implementation to code Caesar’s substitution cipher”

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