RSA/src/MainWindow.java

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.math.BigInteger;

public class MainWindow extends JDialog implements ChangeListener, ActionListener {
    private JPanel contentPane;
    private JTextArea publicKeyTextArea;
    private JTextArea privateKeyTextArea;
    private JTextField plainNumber;
    private JTextField encryptedNumber2;
    private JButton cryptButton;
    private JButton decryptButton;
    private JButton generateKeysButton;
    private JTextField encryptedNumber;
    private JTextField decryptedNumber;
    private JSlider keylength;
    private JLabel keylengthLabel;
    private JTextArea moduleTextArea;
    private JButton moveNumberButton;
    private JButton buttonOK;
    private RSA rsa;

    public MainWindow() {
        setContentPane(contentPane);
        setModal(true);
        getRootPane().setDefaultButton(buttonOK);
        generateKeysButton.addActionListener(this);
        cryptButton.addActionListener(this);
        decryptButton.addActionListener(this);
        keylength.setMinimum(8);
        keylength.setMaximum(50);
        keylength.setMajorTickSpacing(10);
        keylength.setMinorTickSpacing(5);
        keylength.setValue(32);
        keylength.setPaintTicks(true);
        keylength.setPaintLabels(true);
        keylength.addChangeListener(this);
        keylengthLabel.setText(String.valueOf(keylength.getValue()));
        moveNumberButton.addActionListener(this);
    }

    public void stateChanged(ChangeEvent e){
        JSlider source = (JSlider)e.getSource();
        if (source == this.keylength) {
            int value = source.getValue();
            this.keylengthLabel.setText(String.valueOf(value));
        }
    }

    public void actionPerformed(ActionEvent e) {
        JButton source = (JButton) e.getSource();
        if (source == this.cryptButton) {
            try {
                BigInteger message = new BigInteger(this.plainNumber.getText());
                BigInteger key = new BigInteger(this.publicKeyTextArea.getText());
                BigInteger module = new BigInteger(this.moduleTextArea.getText());
                String encrypted = RSA.cipher(message, key, module).toString();
                this.encryptedNumber.setText(encrypted);
            } catch (NumberFormatException ex) {
                JOptionPane.showMessageDialog(this, "Invalid value(s), check your input and try again!", "RSA Test", JOptionPane.ERROR_MESSAGE);
            }

        } else if (source == this.decryptButton) {
            try {
                BigInteger encryNumber = new BigInteger(this.encryptedNumber2.getText());
                BigInteger key = new BigInteger(this.privateKeyTextArea.getText());
                BigInteger module = new BigInteger(this.moduleTextArea.getText());
                String decrypted = RSA.cipher(encryNumber, key, module).toString();
                this.decryptedNumber.setText(decrypted);
            } catch (NumberFormatException ex) {
                JOptionPane.showMessageDialog(this, "Invalid value(s), check your input and try again!", "RSA Test", JOptionPane.ERROR_MESSAGE);
            }

        } else if (source == this.generateKeysButton) {
            this.rsa = new RSA(this.keylength.getValue());
            this.rsa.createKeys();
            this.publicKeyTextArea.setText(this.rsa.getPublicKey()+"");
            this.privateKeyTextArea.setText(this.rsa.getPrivateKey()+"");
            this.moduleTextArea.setText(this.rsa.getRSAModule()+"");
        } else if (source == this.moveNumberButton) {
            this.encryptedNumber2.setText(this.encryptedNumber.getText());
        }
    }

    public static void main(String[] args) {
        MainWindow dialog = new MainWindow();
        dialog.pack();
        dialog.setVisible(true);
        dialog.setSize(800, 600);
        System.exit(0);
    }
}