Question

Part 1 – Data Encryption

Data Encryption is the process of transforming data, using a cipher, to make it unreadable to anyone except those possessing special knowledge. In this problem you will implement a simple encryption technique on data that comprises of non-negative integers that have at least six digits with no leading zeroes. In order to encrypt the number the following functions are to be implemented:
void input(int *num); int add4(int num); int shift(int num); void printOutput(int encryptNum, int originalNum);
The function input is used to read a positive integer having at least six digits and store it in the variable num. All leading zeroes in the input are neglected and are not counted as valid digits. The function will continue requesting for a number until a valid input is provided by the user. A sample run of the function is shown below with data entered by the user displayed using bold font.

Please enter an integer greater than 99999: 2348<enter> Incorrect input.

Please enter an integer greater than 99999: 012345<enter> Incorrect input.

Please enter an integer greater than 99999: 102345<enter> The number entered is 102345

The functions add4 and shift are used to encrypt the number. First, modify the value of each digit of num by adding 4 to the digit. The function add4 modifies the value of each digit of num by adding 4 to each digit,and returns the modified number. Due to addition,if the value of any digit is greater than 9 then subtract 10 from the number so that each digit ranges between 0 and 9. For example, if num is 345678 then add4 should return 789012. Note that the number of digits of the modified number returned by add4 can be less than the number of digits in num. For example, if num is 665325, then add4 returns 009769, which is really 9769.
The input (num) of the function shift is the modified number(output of the function add4). The function shift shifts the position of each digit to the left by one place. The most significant digit becomes the least significant digit.

For example,if the input (num)is 567890 then the output of the function shift is 678905. The modified value is returned by shift and is the final encrypted number. Similar to add4 function, the number of digits returned by shift can be less than the number of digits in num (input to function shift). For example, if num is 107982, then the encrypted number is 79821. The function printOutput prints the original number (originalNum) and the encrypted number (encryptNum). Refer to the examples below for the output format. You are allowed to use the math.h functions in your solution. Remember to add -lm to your gcc command line. Shown below are example runs of the program with data entered by the user displayed using bold font. Given the same user input, your output should match the output exactly, including all punctuation. Any variation from this will result in loss of marks.
• Example 1: Please enter an integer greater than 99999: 4569012<enter> The number entered is 4569012 Original number: 4569012 Encrypted number: 9034568
• Example 2: Please enter an integer greater than 99999: 563918<enter> The number entered is 563918 Original number: 563918 Encrypted number: 73529
• Example 3: Please enter an integer greater than 99999: 70912<enter> Incorrect input. Please enter an integer greater than 99999: 093679<enter> Incorrect input. Please enter an integer greater than 99999: 0877893<enter> The number entered is 877893 Original number: 877893 Encrypted number: 112372
Note: The encrypted number can have less than 6 digits (as shown in Example 2). It is up to the decryption technique to handle this (not part of this problem). In the case of Example 3, 0877893 is a valid input as it has 6 digits without any leading zero (877893)

Develop the code in C programming please

Answer 1

The required code is as follows:

#include <stdio.h>
#include <math.h>

void input(int *num) //function to input the number using its pointer
{
   printf("Please enter an integer greater than 99999: ");
   scanf("%d",num);
   if(*num<=99999)
   {
       printf("Incorrect input. ");
       input(num);
   }
   else
   {
       printf("The number entered is %d ",*num);
   }
}
int add4(int num) //function to add 4 to every digit of the number
{
   int c=1,a=0,r;
   while(num!=0) //we extract every digit from the number, add 4, make it single digit and store it in a
   {
       r=(num%10)+4;
       if(r>=10)
           r=r-10;
       a=a+r*c;
       num=num/10;
       c=c*10;
   }
   return a; //we return a to the main function
}
int shift(int num) //function to shift each digit of number to the left by one place
{
   int copy=num,r,c=1;
   while(copy!=0) //we use this loop to find the most significant bit and its place value(c)
   {
       r=copy%10;
       copy=copy/10;
       c=c*10;
   }
   num=num-(r*c/10); //we delete the most significant bit
   num=num*10+r; //we make it the least significant bit and shift the other digits to the left
   return num; //we return num to the main function
}
void printOutput(int encryptNum, int originalNum)
{
   printf("Original number : %d Encrypted number : %d ",originalNum,encryptNum);
}
int main(void) {
   int num;
   input(&num);
   printOutput(shift(add4(num)),num);
   return 0;
}

Screenshot of output: