Question

1. A company that wants to send data over the Internet will use an encryption program to ensure data security. All data will be transmitted as four-digit integers. The application should read a four-digit integer entered by the user and encrypt it as follows:  Replace each digit with the remainder of the new value divided by 10 by adding 6 to the digit. Then replace the number in the first digit with the third, and the number in the second digit with the fourth. Print the encrypted integer on the screen.  Write a separate application where an encrypted four-digit integer is entered and decrypted (reversing the encryption scheme) and finds the original number.

Note: code should be written in Java Language.

Answer 1

import java.util.*;

public class Main
{
        public static void main(String[] args) {
            Scanner sc= new Scanner(System.in);
                System.out.println("Enter a 4-digit number");
                int n= sc.nextInt();    //input of the number
                int ar[]=new int[4];   //array to store all digits
                int i=3;       //counter variable
                
                while(n>0)     //loop to store each digit in the array
                {
                    ar[i]=n%10;
                    n/=10;
                    i--;
                }
                for( i=0;i<4;i++)    //loop to calculate the original digit of the number
                {
                    ar[i]= (ar[i]+6)%10;
                }
                
                int temp=ar[2];   //swapping 1st and 3rd digit
                ar[2]=ar[0];
                ar[0]=temp;
                
                temp=ar[3];      //swapping 2nd and 4th digit
                ar[3]=ar[1];
                ar[1]=temp;
                
                System.out.println("The original number is :");
                for( i=0;i<4;i++)                  //loop to ptint original digits of the number.
                System.out.print(ar[i]);   
        }
}