Thread: Xoring text with binary file

Hi,

Why can't we xor text with binary file?

When I xor it back half of them are not the same, garbage characters.

Code:

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

string XOR(string value,string key);
void OpenKeyFile();

string value ("The quick brown fox jumps over the lazy dog");
const char * key_file = "C:\\Windows\\System32\\appinfo.dll";
int length_of_command = 200;
char secret_key[520] = "";

int main()
{
    OpenKeyFile();

    string key(secret_key);

    cout<<"Plain text: "<<value<<"\n\n";
    value=XOR(value,key);
    cout<<"Cipher text: "<<value<<"\n\n";
    value=XOR(value,key);
    cout<<"Decrypted text: \n"<<value<<endl;

    return 0;
}

void OpenKeyFile()
{
    fstream ifs(key_file, fstream::in | fstream::binary);
    char a;
    if(!ifs.is_open())
    {
        cout << "Couldnt open input file "<<key_file<<endl;
        return;
    }

    //
    ifs.seekp(0);
    // write to ifs
    ifs.read(secret_key, length_of_command);
    // cout << vIn << endl;
    ifs.close();

}

string XOR(string value,string key)
{
    string retval(value);

    short unsigned int klen=key.length();
    short unsigned int vlen=value.length();
    short unsigned int k=0;
    short unsigned int v=0;

    for(v;v<vlen;v++)
    {
        cout << value[v] << " - " << key[k] << "\n";
        retval[v]=value[v]^key[k];
        k++;
    }

    return retval;
}

string key(secret_key);
This will only copy up to the first \0.

Ah, of course, I should use a vector I guess. Thank you.