(Enforcing Privacy with Cryptography) The explosive growth of Internet communications and data storage on Internet-connected computers has greatly increased privacy concerns. The field of cryptography is concerned with coding data to make it difficult (and hopefully—with the most advanced schemes—impossible) for unauthorized users to read. In this exercise you’ll investigate a simple scheme for encrypting and decrypting data. A company that wants to send data over the In- ternet has asked you to write a program that will encrypt it so that it may be transmitted more se- curely. 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

Question

What will be an ideal response?

Answer 1

```
// Encrypt a number.
#include
using namespace std;

int main()
{
int number; // original number

// enter four-digit number to be encrypted
cout << "Enter a four-digit number: ";
cin >> number;

// encrypt (digit numbers are counted from left)
int digit1 = ( number / 1000 + 7 ) % 10;
int digit2 = ( number % 1000 / 100 + 7 ) % 10;
int digit3 = ( number % 100 / 10 + 7 ) % 10;
int digit4 = ( number % 10 + 7 ) % 10;

int encryptedNumber =
digit1 * 10 + digit2 + digit3 * 1000 + digit4 * 100;

cout << "Encrypted number is " << encryptedNumber << endl;
} // end main
```