XOR and File I/O Problems...

[Junior89]

Hey guys, Im writing a login type program that requires a certain drive to have a certain file on it in order to allow you to enter a username and password. The drive part is done but the password part isn't working. I wrote one program to setup the username and password, XOR them together and save it ina file.

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
     char username[20];
     char password[20];
     cout<<"Set Username: ";
     cin.getline(username, 20);
     cout<<"Set Password: ";
     cin.getline(password, 20);
     char encrypted[20];
     for(int i=0; i<20; i++)
     {
           encrypted[i]=username[i]^password[i];
     }
     ofstream fout("L:/Login/Log-On.txt");
     fout<<encrypted;
     fout.close();
     return 0;
}

Then in the Lgoin pro gram it asks you for you username and password, then XOR's them together the EXACT same way it does in the setup program. Then it STRCMP()'s them together to check. Problem is it never works. I had the program cout<< the different XOR's out (the one from the file and the one from the login program) so i could compare them. They're different, dunno why though. Any ideas? Thanks!

[7stud]

Then in the Lgoin pro gram it asks you for you username and password, then XOR's them together the EXACT same way it does in the setup program.

Prove it.

[swoopy]

> ofstream fout("L:/Login/Log-On.txt");
You should open the file in binary mode:

     ofstream fout("L:/Login/Log-On.txt", ios::binary);

> fout<<encrypted;
You should use write() or put() to output the encypted value:

fout.write(encrypted, strlen(username));

[Junior89]

Prove it.

Ok. They use the exact same process to encode the data in both programs, like i said.

...
for(int i=0; i<20; i++)
{
     encrypt[i]=username[i]^password[i];
}
...

Im not gonna write the same thing twice. I think the problem is that it doesn't save certain characters to the file correctly so when the second program loads the characters from the txt file it loads em different.

[major_small]

a few fundamental problems here:

1. never assume the username OR password have a certain number of characters
2. NEVER assume they both have the SAME AMOUNT of characters
3. you should probably let the user enter less than 20 characters

I don't know about any of the other people on this board, but I don't think I would appreciate anything requiring me to add to my username or password. for example, my username is Major_Small, not Major_Small123456789, and my password is password, not passwordwithextrachr.

[Salem]

Consider
Username: Fred
Password: Fred
What is your encrypted text?