Two-factor authentication with Google Authenticator - manually type key instead of scanning QR code

key = secret

The key should be the same as the secret you generated. Just test it by opening google authenticator and manually adding it as the key.

Check out the docs at the link below: https://support.google.com/accounts/answer/1066447?co=GENIE.Platform%3DiOS&hl=en

The Google Authenticator Setup QR code is generated based on a few things, one of these is the "secret key", so depending on the codebase you are using to build it into your site the "secret key" is normally generated first and that key is then used to generate the QR code.

If you look at this node.js module you can see what I am talking about

// generate base32 secret
var secret = GA.encode('base 32 encoded user secret') || GA.secret();

// get QRCode in SVG format
var qrCode = GA.qrCode('akanass', 'otp.js', secret);

https://github.com/njl07/otp.js/#qrcode-generation

Here is another example site where you can manually generate the QR code, You can provide a Label, User, Key and URL, and that will then generate the QR code.

https://dan.hersam.com/tools/gen-qr-code.html

Let me know what codebase you are trying to use to implement this into your site then I can help you track down where the secret key is generated

And View

@model _2FAGoogleAuthenticator.ViewModel.LoginModel

@{
    ViewBag.Title = "Login";
}

<h2>Login</h2>

@* Here we will add 2 form, 1 for Login and another one for 2FA token verification form *@
@if (ViewBag.Status == null || !ViewBag.Status)
{
    <!--Show login form here, Viewbag.Status is used for check is already veirfied from our database or not-->
    <div>@ViewBag.Message</div>
    <div>
        @using (Html.BeginForm())
        {
            <div class="form-group">
                <label for="Username">Username : </label>
                @Html.TextBoxFor(a => a.Username, new { @class = "form-control"})
            </div>
            <div class="form-group">
                <label for="Password">Password : </label>
                @Html.TextBoxFor(a => a.Password, new { @class="form-control", type="password"})
            </div>
            <input type="submit" value="Login" class="btn btn-default" />
        }
    </div>
}
else
{
    <!--Show 2FA verification form here-->
    <div>@ViewBag.Message</div>
    <div>
        <img src="@ViewBag.BarcodeImageUrl"/>
    </div>
    <div>
        **Manual Setup Code : @ViewBag.SetupCode**
    </div>
    <div>
        @using (Html.BeginForm("Verify2FA","Home", FormMethod.Post))
        {
            <input type="text" name="passcode" />
            <input type="submit" class="btn btn-success" /> 
        }
    </div>
}

public class HomeController : Controller
    {
        private const string key = "key"; // any 10-12 char string for use as private key in google authenticator
        public ActionResult Login()
        {
            return View();
        }

        [HttpPost]
        public ActionResult Login(LoginModel login)
        {
            string message = "";
            bool status = false;

            //check username and password form our database here
            //for demo I am going to use Admin as Username and Password1 as Password static value
            if (login.Username == "sanket" && login.Password == "123")
            {
                status = true; // show 2FA form
                message = "2FA Verification";
                Session["Username"] = login.Username;

                //2FA Setup
                TwoFactorAuthenticator tfa = new TwoFactorAuthenticator();
                string UserUniqueKey = login.Username + key; //as Its a demo, I have done this way. But you should use any encrypted value here which will be unique value per user 
                Session["UserUniqueKey"] = UserUniqueKey;
                var setupInfo = tfa.GenerateSetupCode("Sanket Security", login.Username, UserUniqueKey, 300, 300);
                ViewBag.BarcodeImageUrl = setupInfo.QrCodeSetupImageUrl;
                ViewBag.SetupCode = setupInfo.ManualEntryKey;
            }
            else
            {
                message = "Invalid credential";
            }
            ViewBag.Message = message;
            ViewBag.Status = status;
            return View();
        }

        public ActionResult MyProfile()
        {
            if (Session["Username"] == null || Session["IsValid2FA"] == null || !(bool)Session["IsValid2FA"])
            {
                return RedirectToAction("Login");
            }
            ViewBag.Message = "Welcome " + Session["Username"].ToString();
            return View();
        }
        public ActionResult Verify2FA()
        {
            var token = Request["passcode"];
            TwoFactorAuthenticator tfa = new TwoFactorAuthenticator();
            string UserUniqueKey = Session["UserUniqueKey"].ToString();
            bool isValid = tfa.ValidateTwoFactorPIN(UserUniqueKey, token);
            if (isValid)
            {
                Session["IsValid2FA"] = true;
                return RedirectToAction("MyProfile", "Home");
                token=string.Empty;
            }
            return RedirectToAction("Login", "Home");
        }
    }
}