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

//Text file called pwlist.txt
//Duncan,WANIS
//James,OOIWDFV

void main(){
    map<string,string> pws;

    ifstream pf("pwlist.txt");
    for(string pw, user, line; pf.good() && getline(pf,line);pws.insert(pair<string,string>(user,pw)))
    {
        stringstream strm(line);
        getline(strm,user,',');
        getline(strm,pw,',');
    };
    pf.close();

    string username, password;
    cout<<"Please enter username:\n";
    cin>>username;
    cout<<"Please enter password:\n";
    cin>>password;

    for( unsigned int i = 0; i < password.size(); ++i )
    {
        //A little bit encrpyted just to spice things up
        password[i] = 'A'+(password[i]^username[i%username.size()])%26;
    }

    if ( pws.find(username) != pws.end() && pws.find(username)->second == password )
    {
        cout<<"Correct Login Well Done!\n";
    }
    else
        cout<<"Incorrect please do not try again!\n";

    //Now to see if we can create a cracker.
    //The encrypted password is what needs to be modified we want another password that will colide
    //Assume we know the first pw char is W and real pw is R and the username is Duncan
    //R^D = 82^68 = 22
    //22%26 = 22
    //22+'A' = 'W'
    //So we need something else that creates W
    //So we need something so that x%26 = 22
    //x could be 22+26*anything lets try 48
    //So what ^ with 'D' = 48 well 116 does
    //116 = 't' therefore t would work instead of 'R'
    //And sure enough that came out correct so we have a collision.

    //We can work out all possible passwords from the password list as follows.
    //Remember max char is 128 128/26 = ~4.9
    //Assume passwords are in the range 32-126 ie special chars, chars, numerical

    username = "James";
    string encryptedpw = pws.find(username)->second;

    for( unsigned int i = 0; i < encryptedpw.size(); ++i )
    {
        int beforemod = encryptedpw[i]-'A';
        cout<<"Character "<<i<<" is one of: ";
        for( ; beforemod < 128; beforemod+=26 )
        {
            char possible = (char)beforemod^username[i%username.size()];
            if ( possible > 31 && possible < 127 ){
                cout<<possible<<", ";
            }
        }
        cout<<endl;
    }
    //From this response it is clear that it would still take a small amount of work to
    //calculate the original. Although ultimatly it doesn't matter as we have now a list
    //of valid passwords.

    //Pause until we are done
    cin>>username;
}