Question

How to write a program in order to find the key?

Given a ciphertext message that was generated using the XOR cipher and a bit string found in the plaintext, find the key that can be used to map the plaintext to the ciphertext. The key size is 32 bits.

Answer 1

using java program:

import java.io.*;
import javax.swing.JOptionPane;
  
   public class XOR
   {
  
        public static void main(String[] args)
        {
          
            String str = (JOptionPane.showInputDialog("Input Plaintext:"));
           
          
         String str1 = (JOptionPane.showInputDialog("Input ciphertext:"));
            int Length=str1.length();
                
           
            //prints key
            String key = key(str,Length);
            System.out.println("key:" + key);
  
          
        }
  
        public static String key(String str, int Length)
        {
            String key = "";
            for(int i = 0; i < str.length(); i++)
            {
                int c = str.charAt(i);
               
                if (Character.isUpperCase(c))
                {
                    //26 letters of the alphabet so mod by 26
                    c = c + (Length % 26);
                    if (c > 'Z')
                    c = c - 26;
                }
                else if (Character.isLowerCase(c))
                {
                    c = c + (Length % 26);
                    if (c > 'z')
                    c = c - 26;
                }
                key += (char) c;
            }
        return key;
        }
         
   }