Question

It’s been a long time since I’ve touched C++ and I’ve never been quite fluent in the language, so forgive my ignorance.

I’ve written the following little program to mess around with XOR encryption:

#include <iostream>
#include <iomanip>
#include "string.h"

using std::cout;
using std::endl;
using std::hex;
using std::string;

string cipher(string msg, char key);

int main(void)
{
    string msg = "Now is the winter of our discontent, made glorious summer by this sun of York.";
    char key = 's';  // ASCII 115

    string ctext = cipher(msg, key);

    cout << "Plaintext:  " << msg << endl;
    cout << "Ciphertext (hex):  ";
    for (int i = 0; i < ctext.size(); i++)
        cout << hex << ctext[i];

    return 0;
}

string cipher(string msg, char key)
/*
    Symmetric XOR cipher
*/
{
    for(int i = 0; i < msg.size(); i++)
        msg[i] ^= key;

    return msg;
}

This code outputs the following:

Plaintext:  Now is the winter of our discontent, made glorious summer by this sun of York.
Ciphertext (hex):  =SSSSSS_SSSS
SSSS*]

Why can I not get the hex values to output? What am I doing wrong?

Also, any general advice is appreciated.

Answer 1

Hex applies to integers. A char is streamed as a character regardless of what the base is set in the stream. If you want the ACSII code of the character to be printed in hex, use

 cout << hex << static_cast<int>(ctext[i]);