A company that want 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 transmitted as four digit intergers. Your application should read a four digit integer enterd 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 diving the new value by 10.Tjen swap the first digit with the third, and swap the second digit with the fourth. Then print the encrpted interger. Write a separate application that inputs an encrypted four digit interger and decrypts it (by reversing the encryption scheme) to form the original number

A java code was used to write a program that will encrypt and secure a company data that is transmitted over the Internet.

The Java code is shown below

Explanation:

Solution:

CODE IN JAVA:

Encryption.java file:

import java.util.Scanner;

public class Encryption {

  public static String encrypt(String number) {

      int arr[] = new int[4];

      for(int i=0;i<4;i++) {

          char ch = number.charAt(i);

          arr[i] = Character.getNumericValue(ch);

      }

      for(int i=0;i<4;i++) {

          int temp = arr[i] ;

          temp += 7 ;

          temp = temp % 10 ;

          arr[i] = temp ;

      }

      int temp = arr[0];

      arr[0] = arr[2];

      arr[2]= temp ;

      temp = arr[1];

      arr[1] =arr[3];

      arr[3] = temp ;

      int newNumber = 0 ;

      for(int i=0;i<4;i++)

          newNumber = newNumber * 10 + arr[i];

      String output = Integer.toString(newNumber);

      if(arr[0]==0)

          output = "0"+output;

      return output;

  }

  public static String decrypt(String number) {

      int arr[] = new int[4];

      for(int i=0;i<4;i++) {

          char ch = number.charAt(i);

          arr[i] = Character.getNumericValue(ch);

      }

      int temp = arr[0];

      arr[0]=arr[2];

      arr[2]=temp;

      temp = arr[1];

      arr[1]=arr[3];

      arr[3]=temp;

      for(int i=0;i<4;i++) {

          int digit = arr[i];

          switch(digit) {

              case 0:

                  arr[i] = 3;

                  break;

              case 1:

                  arr[i] = 4;

                  break;

              case 2:

                  arr[i] = 5;

                  break;

              case 3:

                  arr[i] = 6;

                  break;

              case 4:

                  arr[i] = 7;

                  break;

              case 5:

                  arr[i] = 8;

                  break;

              case 6:

                  arr[i] = 9;

                  break;

              case 7:

                  arr[i] = 0;

                  break;

              case 8:

                  arr[i] = 1;

                  break;

              case 9:

                  arr[i] = 2;

                  break;

          }

      }

     int newNumber = 0 ;

      for(int i=0;i<4;i++)

          newNumber = newNumber * 10 + arr[i];

      String output = Integer.toString(newNumber);

      if(arr[0]==0)

          output = "0"+output;

      return output;    

  }

  public static void main(String[] args) {

      Scanner sc = new Scanner(System.in);

      System.out.print("Enter a 4 digit integer:");

      String number = sc.nextLine();

      String encryptedNumber = encrypt(number);

      System.out.println("The decrypted number is:"+encryptedNumber);

      System.out.println("The original number is:"+decrypt(encryptedNumber));  

  }  

}

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