Question

A company that wants to send data over the Internet has asked you to write a program that will encrypt it so that it may be transmitted more securely. All the data is transmitted as four-digit integers. Your application should read a four-digit integer entered by the user and encrypt it as follows: Replace each digit with the result of adding 7 to the digit and getting the remainder after dividing the new value by 10. Then swap the first digit with the third, and swap the second digit with the fourth. Then print the encrypted integer. Write a separate application that inputs an encrypted four-digit integer and decrypts it (by reversing the encryption scheme) to form the original number.

Java version!

Answer 1

`Hey,

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import java.util.Scanner;
public class Test{

public static int encrypt( int n)
{
   // obtain digits of number
   int a = n / 1000;
   int b = (n % 1000) / 100;
   int c = (n % 100) / 10;
   int d = n % 10;
   // Replace each digit with the result of adding 7 to the digit and getting
   // the remainder after dividing the new value by 10.
   a = (a + 7) % 10;
   b = (b + 7) % 10;
   c = (c + 7) % 10;
   d = (d + 7) % 10;
   return (c * 1000 + d * 100 + a * 10 + b); // swap a-c and b-d; generate result number
}

public static int decrypt( int n)
{
   // obtain digits of number
   int a = n / 1000;
   int b = (n % 1000) / 100;
   int c = (n % 100) / 10;
   int d = n % 10;
   // Replace each digit with the result of substract 7 to the digit and getting
   // the remainder after dividing the new value by 10.
   a = (a + 3) % 10;
   b = (b + 3) % 10;
   c = (c + 3) % 10;
   d = (d + 3) % 10;
   return (c * 1000 + d * 100 + a * 10 + b);
}

public static void main(String []args){
Scanner sc=new Scanner(System.in);
    int n;
   System.out.println("Enter four-digit number: ");
   n=sc.nextInt();
   System.out.println("Encrypted number is: "+encrypt(n));
   System.out.println("Number after encrypt-decrypt cycle is: "+decrypt(encrypt(n)));
}
}

Kindly revert for any queries

Thanks.