Password Generator in C++ using Qt

By ROHAN DAS

I've made a Password Generator using C++ in Qt, which will generate a password between length 5-50 characters. The logics are written in C++, but the UI is made using Qt.

A password is a string of characters that is used for the verification of the identity of users.

What is a good password?

1. A good password should have a decent length; it shouldn't be too long or too short.
2. It should consist alphabets(both lowercase and uppercase), numbers and special characters.
3. It shouldn't be easily guessed.

Steps to create a Password Generator in Qt:

Step 1: Install Qt in your machine.

Step 2: Create a Widget Application in it.

Step 3: Now, in mainwindow.ui we have to add 2 labels, 1 textEdit, 1 textBrowser and 1 pushButton. The textEdit is used to take input from the user and the textBrowser is used to show the generated password.

Step 4: Now, we have to write the necessary logic to generate password in void MainWindow::on_genPas_clicked(){} inside the mainwindow.cpp . But before that we have to include the necessary libraries for this work. The necessary libraries are:

#include "QMessageBox"
#include "iostream"
#include "string"
#include "QPixmap"
#include "QFile"
#include "QTextStream"

Step 5: Now let's talk about the main logics. 

//passLen is a QString(similar to the String in C++) Object which stores the String entered in the QLineEdit under the label 'Enter Length'
QString passLen=ui->inpTxt->text();

bool converted; //It is a Boolean Variable which stores either true or false

int len=passLen.toInt(&converted);  //len is an Integer variable whcich stores the integer converted version of the object passLen
//An interesting thing here, if all the characters of the Qstring passLen is integer then the boolean variable 'converted' is set to 1; otherwise it is set to 0

If the entered string is fully convertible to in then we go to step 6.

Step 6: Then we generate a random password using the following code.

//First we declare an empty QString Object
            QString password="";

            //With the help of these objects we'll create our password
            QString alphabet_lower="abcdefghijklmnopqrstuvwxyz";
            QString alphabet_upper="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            QString symbols="!@#$%&";
            QString number="0123456789";

            //Ineger objects
            int key,count_alpha_lwr=0,count_alpha_uppr=0,count_symbols=0,count_number=0;

            int c=0;
            while(c<len){
                int k=rand()%4+1;   //Generates a Random Number between 1 to 4

                if(c==0){
                    k%=3;
                    if(k==0)
                        ++k;
                }
                switch(k){
                    case 1:/*This block will help to add lowercase alphabets in the password*/{
                        if((count_alpha_lwr==2)&&(count_number==0||count_alpha_uppr==0||count_alpha_uppr==1||count_symbols==0))
                            break;
                        int key=rand()%26;
                        password=password+alphabet_lower[key];
                        count_alpha_lwr++;
                        c++;
                        break;
                }

                case 2:/*This block will help to add uppercase alphabets in the password*/{
                        if((count_alpha_uppr==2)&&(count_number==0||count_alpha_lwr==0||count_alpha_lwr==1||count_symbols==0))
                            break;
                        key=rand()%26;
                        password=password+alphabet_upper[key];
                        count_alpha_uppr++;
                        c++;
                        break;
                }
                case 3:/*This block will help to add digits in the password*/{
                        if((count_number==1)&&(count_alpha_lwr==0||count_alpha_lwr==1||count_alpha_uppr==1||count_alpha_uppr==0||count_symbols==0))
                            break;
                        key=rand()%10;
                        password=password+number[key];
                        count_number++;
                        c++;
                        break;
                }
                case 4:/*This block will help to symbols in the password*/{
                        if((count_symbols==1)&&(count_alpha_lwr==0||count_alpha_lwr==0||count_alpha_lwr==1||count_alpha_uppr==0||count_alpha_uppr==1||count_number==0))
                            break;
                        key=rand()%6;
                        password=password+symbols[key];
                        count_symbols++;
                        c++;
                        break;
                }
                }
            }

Step 7: After the password is successfully created we show a messageBox on the screen and show the generated password in the textBrowser using the following code:

//After the password creation is complete, this QMesaageBox will show the password
            QMessageBox::information(this,"Your Password is Ready","Thanks for using");
            QFile file("E:\\Internships\\1. C++ - Codespeedy Technology\\Projects\\Project 1\\passwordGenerator\\password.txt");
            if(!file.open(QFile::WriteOnly|QFile::Text)){
                QMessageBox::warning(this,"No file","No file like this");
            }
            QTextStream out(&file);
            QString text=password;
            out<<text;
            file.flush();
            file.close();

            QFile disp("E:\\Internships\\1. C++ - Codespeedy Technology\\Projects\\Project 1\\passwordGenerator\\password.txt");
            if(!disp.open(QIODevice::ReadOnly))
                QMessageBox::information(0,"No file like this","No file like this");
            QTextStream dsp(&disp);
            ui->textBrowser->setText(dsp.readAll());

Here we created a file to store the last password generated.

Step 8: Build and Run the following code.