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Taking password as input in C++
  • Difficulty Level : Hard
  • Last Updated : 18 Jan, 2021

There are two methods in which input can be taken in a more secure way:

  • Do not display any content.
  • Display a special character such as an asterisk instead of actual content.

In this method, input content will be invisible. This can be implemented in two ways:

using <windows.h>:

Program 1:

Below is the program where console mode is set to enable, echo input, and reset the console mode:

C++



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// C++ program to take the input
// invisibly
#include <iostream>
#include <windows.h>
using namespace std;
  
// Function take password and
// reset to console mode
std::string takePasswdFromUser()
{
    HANDLE hStdInput
        = GetStdHandle(STD_INPUT_HANDLE);
    DWORD mode = 0;
  
    // Create a restore point Mode
    // is know 503
    GetConsoleMode(hStdInput, &mode);
  
    // Enable echo input
    // set to 499
    SetConsoleMode(
        hStdInput,
        mode & (~ENABLE_ECHO_INPUT));
  
    // Take input
    string ipt;
    getline(cin, ipt);
  
    // Otherwise next cout will print
    // into the same line
    cout << endl;
  
    // Restore the mode
    SetConsoleMode(hStdInput, mode);
  
    return ipt;
}
  
// Driver Code
int main()
{
    string input;
    cout << "@root>>> ";
  
    // Function Call
    input = takePasswdFromUser();
  
    // Print the input
    cout << input << endl;
}

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Output:

using <conio.h>: 

For this getch() is used. This function takes a character input from user without buffer and doesn’t wait for the user to press “return” key.

Program 2:

Below is the C++ program to demonstrate the use of getch() in conio.h:

C++

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// C++ program to demonstrate the
// use of getch()
#include <conio.h>
#include <iostream>
using namespace std;
  
// Function using getch()
std::string takePasswdFromUser()
{
    string ipt = "";
    char ipt_ch;
    while (true) {
        ipt_ch = getch();
  
        // Check whether user enters
        // a special non-printable
        // character
        if (ipt_ch < 32) {
            cout << endl;
            return ipt;
        }
        ipt.push_back(ipt_ch);
    }
}
  
// Driver Code
int main()
{
    string input;
    cout << "@root>>> ";
  
    // Funciton call
    input = takePasswdFromUser();
    cout << input << endl;
}

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Output:



Drawback: The user can’t clear the response made earlier. When backspace is pressed, the input is returned.

Program 3:

Below is the C++ program to demonstrate the solution to the above drawback:

C++

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// C++ program to demonstrate the
// solution of above drawback
#include <conio.h>
#include <iostream>
using namespace std;
  
// Enumerator
enum TT_Input {
  
    // ASCII code of backspace is 8
    BACKSPACE = 8,
    RETURN = 32
};
  
// Function accepting password
std::string takePasswdFromUser()
{
    string ipt = "";
    char ipt_ch;
    while (true) {
        ipt_ch = getch();
  
        if (ipt_ch < TT_Input::RETURN
            && ipt_ch != TT_Input::BACKSPACE) {
            cout << endl;
            return ipt;
        }
  
        // Check whether the user
        // pressed backspace
        if (ipt_ch == TT_Input::BACKSPACE) {
  
            // Check if ipt is empty or not
            if (ipt.length() == 0)
                continue;
            else {
  
                // Removes last character
                ipt.pop_back();
  
                continue;
            }
        }
        ipt.push_back(ipt_ch);
    }
}
  
// Driver Code
int main()
{
    string input;
    cout << "@root>>> ";
  
    // Function call
    input = takePasswdFromUser();
    cout << input << endl;
}

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Hiding the password by a special character(*):

The idea is to use the library <conio.h> here to hide password with asterisk(*). Below is the C++ program using conio.h to hide the password using *:

Program 4:

C++

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// C++ program to hide the password
// using *(asterik)
#include <conio.h>
#include <iostream>
using namespace std;
  
// Enumerator
enum IN {
  
    // 13 is ASCII for carriage
    // return
    IN_BACK = 8,
    IN_RET = 13
  
};
  
// Function that accepts the password
std::string takePasswdFromUser(
    char sp = '*')
{
    // Stores the password
    string passwd = "";
    char ch_ipt;
  
    // Until condition is true
    while (true) {
  
        ch_ipt = getch();
  
        // if the ch_ipt
        if (ch_ipt == IN::IN_RET) {
            cout << endl;
            return passwd;
        }
        else if (ch_ipt == IN::IN_BACK
                 && passwd.length() != 0) {
            passwd.pop_back();
  
            // Cout statement is very
            // important as it will erase
            // previously printed character
            cout << "\b \b";
  
            continue;
        }
  
        // Without using this, program
        // will crash as \b can't be
        // print in beginning of line
        else if (ch_ipt == IN::IN_BACK
                 && passwd.length() == 0) {
            continue;
        }
  
        passwd.push_back(ch_ipt);
        cout << sp;
    }
}
  
// Driver Code
int main()
{
    string input;
    cout << "@root>>> ";
  
    // Function call
    input = takePasswdFromUser();
    cout << input << endl;
}

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