One time password (OTP) generator for Qt

Works with both TOTP and HOTP with variable length.

Installation

First clone this repository (or add it as a submodule if you use git):

• Standalone: git clone https://github.com/RikudouSage/QtOneTimePassword.git otp
• Submodule: git submodule add https://github.com/RikudouSage/QtOneTimePassword.git otp

The last argument is the target directory, otp in this case, it can be anything.

Then you add it to either your qmake .pro file or the your CMakeLists.txt (replace otp if you've cloned the repo in a different dir):

qmake:

SOURCES += otp/onetimepasswordgenerator.cpp
HEADERS += otp/onetimepasswordgenerator.h

cmake - add the files to your add_executable instruction:

add_executable(your-app-name
  otp/onetimepasswordgenerator.cpp otp/onetimepasswordgenerator.h
  main.cpp
)

Usage

The usage is pretty straightforward, but anyway here's an example:

#include <QCoreApplication>
#include <QDebug>

#include "otp/onetimepasswordgenerator.h"

QByteArray decodeBase32(const QString &input); // assume you have this function defined somewhere

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);

    const auto secret = app.arguments().at(1); // take the base32 encoded string from the first argument as a secret

    OneTimePasswordGenerator totp;
    qDebug() << totp.generateHOTP(secret, 10, 6); // create a HOTP, the counter is set to 10, the digits count is set to 6
    qDebug() << totp.generateTOTP(secret, 6); // create a TOTP, the digits count is set to 6
    
    // using directly with base32 decoded raw bytes
    qDebug() << totp.generateHOTP(decodeBase32(secret), 10, 6);
    qDebug() << totp.generateTOTP(decodeBase32(secret), 6);

    return 0;
}

The string accepting functions are also invokable from QML:

// main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>

#include "otp/onetimepasswordgenerator.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));

    // register the generator as a qml type within com.vendor
    qmlRegisterType<OneTimePasswordGenerator>("com.vendor", 1, 0, "OneTimePasswordGenerator");

    engine.load(url);

    return app.exec();
}

// main.qml
import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15

// import the registered C++ objects
import com.vendor 1.0

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("TOTP generator")

    property string totp
    property string hotp

    // initialize an OneTimePasswordGenerator and give it an id by which it can be accessed
    OneTimePasswordGenerator {
        id: otpGenerator
    }

    Column {
        width: parent.width
        spacing: 10
        TextField {
            id: totpSecret
            placeholderText: "Input the secret"
            width: parent.width
            onTextChanged: {
                // here you call the methods of the C++ OneTimePasswordGenerator
                hotp = otpGenerator.generateHOTP(text, hotpCounter.text || 0, 6);
                totp = otpGenerator.generateTOTP(text, 6);
            }
        }
        TextField {
            id: hotpCounter
            placeholderText: "Input the counter value (only for HOTP)"
            width: parent.width
            inputMethodHints: Qt.ImhDigitsOnly
        }

        Text {
            text: "TOTP: " + totp
        }
        Text {
            text: "HOTP: " + hotp
        }

        Button {
            text: qsTr("Regenerate")
            onClicked: {
                totpSecret.textChanged();
            }
        }
    }
}