Question

Write a program that encrypts and decrypts a string of characters. Use a char array for this, not the string class. The maximum length of a string input to the program will be 200 characters. The input may contain blanks and other whitespace. Your program must request a c-string from the user and encrypt it as described below. If the user enters a single asterisk as the only thing on a line, the program should stop. Otherwise, encrypt the string, then display the encrypted version. Decrypt it using the inverse of the algorithm below and display the result. This should be the original string. Then go back and request another string.

Answer 1

Answer:

C++ code for encryption is given below

Explanation:

#include <iostream>

using namespace std;

//functions to encrypt and decrypt

void encrypt(char str[]);

void decrypt(char str[]);

int main(){

char str[200];

bool done = false;

while(!done){

cout << "Enter a string (enter * to stop): ";

cin.getline(str, 200);

if(str[0] == '*' && str[1] == '\0')

done = true;

else{

encrypt(str);

cout << "Encrypted: " << str << endl;

decrypt(str);

cout << "Decrypted: " << str << endl;

}

cout << endl;

}

}

void encrypt(char str[]){

int i = 1;

for(int j = 0; str[j] != '\0'; j++){

str[j] += i;

i++;

if(i == 11)

i = 1;

}

}

void decrypt(char str[]){

int i = 1;

for(int j = 0; str[j] != '\0'; j++){

str[j] -= i;

i++;

if(i == 11)

i = 1;

}

}