C++ Encrypting a File\'s Data (You may only use the headers #include<algorithm>

Question

C++ Encrypting a File's Data (You may only use the headers #include<algorithm> #include<fstream> and #include<string>)

4) Required function: void encrypt_file(const std::string& filename, const std:string& password) You realized that someone else might see through your idea to "unzip" a file and determine it is not secure enough to transmit these files, so you thought encryption might be a better way to secure your pictures. To do some basic encryption, you have decided to take a password as an encryption key and then repeatedly XOR the file data with the password and write out this data as a new file. To accomplish this, we have to understand first how XOR works. The bitwise operation in C++ is computed using the A operator works on all primitive types. The XOR operation behaves as follows: Table 1: Truth table for XOR (source: http://www.cplusplus.com/doc/boolean/) aba b 011 00 1 !) A "bitwise" operator takes two variables and evaluates a logical operator on respective bits of the variables. Consider the following code:

Explanation / Answer

#include <iostream>
#include <fstream>
using namespace std;

void encrypt_file(const std::string& filename, const std::string password){

streampos size;
char * memblock;
string in;
string out;

in = filename;
out = filename + "-encrypted";

ifstream file (in.c_str(), ios::in|ios::binary);
ofstream ofile (out.c_str(), ios::out|ios::binary);

if (file)
{
    file.seekg (0, ios::end);
    size = file.tellg();
    memblock = new char [size];
    file.seekg (0, ios::beg);
    file.read (memblock, size);
    file.close();
   
   
    int j = 0;
    for (int i = 0; i<size; i = i++){
       memblock[i] = memblock[i] ^ password[j];
       j = (j + 1) % password.size();
       
    }
    for (int i = 0; i<size; i = i++){
        ofile.write(&memblock[i],1);
    }
       
    ofile.close();  

    delete[] memblock;
   }
}

int main () {
string filename;

cout << "Enter file name :" << endl;
cin >> filename;
encrypt_file(filename, "cse250cse250cse2");
}

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