алгоритм RSA

package myrsa;
 
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.JTextField;
 
 
public class MyRsa extends JFrame {
    
    /** initialization variable for two distinct prime numbers */
    private final static int P = 7;
    private final static int Q = 17;
    /** initialization variable for module */
    private int n = 0;
    /** initialization variable for result Euler's totient function */
    private int f = 0;
    /** initialization variable for public exponent */
    private int e = 5;
    /** initialization variable for secret exponent */
    private int d = 0;
    /** initialization array for the source characters */
    private char sourceCharacters[];
    /** initialization array for the encrypted characters like code*/
    private int encryptedIntCharacters[];
    /** initialization array for the encrypted characters */
    private char encryptedCharacters[];
    /** initialization array for the decrypted characters */
    private char decryptedCharacters[];
    
    private JLabel l1;
    private JLabel l2;
    private JLabel l3;
    private JTextField tf1;
    private JTextField tf2;
    private JTextField tf3;
    private JButton encrypt;
    private JButton decrypt;
 
    /** 
     * Construct
     */
    public MyRsa() {
        //compute module
        n = P * Q; 
        //compute Euler's totient function
        f = (P - 1) * (Q - 1); 
        //compute secret exponent
        d = computeD();
    }
    
    private void initComponents() {
        this.setTitle("RSA");
        this.setSize(350, 200);
        this.setVisible(true);
        this.setResizable(false);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setLayout(null);
        
        l1 = new JLabel("Source message: ");
        l1.setBounds(10, 10, 120, 20);
        this.add(l1);
        l2 = new JLabel("Encrypted message: ");
        l2.setBounds(10, 50, 120, 20);
        this.add(l2);
        l3 = new JLabel("Decrypted message: ");
        l3.setBounds(10, 90, 120, 20);
        this.add(l3);
        
        encrypt = new JButton("encrypt");
        encrypt.setBounds(70, 130, 100, 20);
        encrypt.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String sourceMessage = tf1.getText();
                sourceCharacters = sourceMessage.toCharArray();
                encryptMessage();
            }
        });
        this.add(encrypt);
        decrypt = new JButton("decrypt");
        decrypt.setBounds(190, 130, 100, 20);
        decrypt.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
              decryptMessage();
            }
        });
        this.add(decrypt);
        
        tf1 = new JTextField();
        tf1.setBounds(135, 10, 200, 20);
        this.add(tf1);
        tf2 = new JTextField();
        tf2.setBounds(135, 50, 200, 20);
        this.add(tf2);
        tf3 = new JTextField();
        tf3.setBounds(135, 90, 200, 20);
        this.add(tf3);
    }
    
    /**
     * Method for compute secret exponent
     * @return secret exponent
     */
    private int computeD() {
        for (int d = 1; ; d++) {
            if ( (d * e) % f == 1 ) {
                return d;
            } 
        }
    }
    
    /**
     * Method for encrypting messages
     * @param msg incoming message
     */
    public void encryptMessage() {
        System.out.println("n: " + n);
        encryptedIntCharacters = new int[sourceCharacters.length];
        encryptedCharacters = new char[sourceCharacters.length];
        int enc = 0;
        for (int i = 0; i < sourceCharacters.length; i++) {
            enc = (int) sourceCharacters[i];
            System.out.println("d: " + d);
            System.out.println("code: " + enc);
            double a = java.lang.Math.pow(enc,e);
            System.out.println("enc ^ e: " + a);
            encryptedIntCharacters[i] = (int)a % n;
            System.out.println("c :" + encryptedIntCharacters[i]);
            encryptedCharacters[i] = Character.toChars(encryptedIntCharacters[i])[0];
        }
        StringBuffer encString = new StringBuffer();
        for (int i = 0; i < encryptedCharacters.length; i++) {
            encString.append(encryptedCharacters[i]);
        }
        tf2.setText(encString.toString());
    }
    
    public void decryptMessage() {
        decryptedCharacters = new char[encryptedCharacters.length];
        System.out.println("n: " + n);
        System.out.println("d: " + d);
        int dec = 0;
        for (int i = 0; i < decryptedCharacters.length; i++) {
            double a = java.lang.Math.pow(encryptedIntCharacters[i], d);
            System.out.println(a);
            dec = (int)a % n;
            System.out.println("dec: " + dec);
            decryptedCharacters[i] = Character.toChars(dec)[0];
        }
        StringBuffer decString = new StringBuffer();
        for (int i = 0; i < decryptedCharacters.length; i++) {
            decString.append(decryptedCharacters[i]);
        }
        tf3.setText(decString.toString());
    }
 
    /** 
     * Method main
     * @param args array of options
     */
    public static void main(String[] args) {
        System.out.println(Character.toChars(19));
       MyRsa rsa = new MyRsa();
       rsa.initComponents();
    }
}