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Code Sample: Standard Mode Phone Verification

Published: May 20, 2013

Updated: June 24, 2015

This code sample shows you how to use the APIs in the Azure Multi-Factor Authentication SDK to add standard mode voice call verification to your application. Standard mode is a telephone call that the user responds to by pressing the # key.

This example uses the C# .NET 2.0 Multi-Factor Authentication SDK in a basic ASP.NET application with C# server-side logic, but the process is very similar for simple implementations in other languages. Because the SDK includes source files, not executable files, you can build the files and reference them or include them directly in your application.

The Azure Multi-Factor Authentication SDK is available in C#, Java, VB, Perl, and PHP. For more information about downloading the SDK, see Using the Multi-Factor Authentication SDK.

securitySecurity Note
When implementing Multi-Factor Authentication, use the additional factors as secondary or tertiary verification to supplement your primary authentication method. These methods are not designed to be used as primary authentication methods.

This sample code for a very simple web demo application uses a telephone call with a # key response to complete the user's authentication. This telephone call factor is known in Multi-Factor Authentication as standard mode.

The client-side code does not include any Multi-Factor Authentication-specific elements. Because the additional authentication factors are independent of the primary authentication, you can add them without changing the existing sign-on interface. The APIs in the Multi-Factor SDK let you customize the user experience, but you might not need to change anything at all.

The server-side code adds standard-mode authentication in Step 2. It creates a PfAuthParams object with the parameters that are required for standard-mode verification: username, telephone number, and mode, and the path to the client certificate (CertFilePath), which is required in each call. For a demonstration of all parameters in PfAuthParams, see the Example file in the SDK.

Next, the code passes the PfAuthParams object to the pf_authenticate() function. The return value indicates the success or failure of the authentication. The out parameters, callStatus and errorID, contain additional call result information. The call result codes are documented in the call results file in the SDK.

This minimal implementation can be written in a just a few lines. However, in production code, you would include more sophisticated error handling, additional database code, and an enhanced user experience.

The following is web client code for a demo page.

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Multi-Factor Authentication Demo</title>
    <h1>Azure Multi-Factor Authentication Demo</h1>
    <form id="form1" runat="server">

    <div style="width:auto; float:left">
        Username:&nbsp;<br />
        Password:&nbsp;<br />

        <asp:TextBox id="username" runat="server" width="100px"/><br />
        <asp:Textbox id="password" runat="server" width="100px" TextMode="password" /><br />

    <asp:Button id="btnSubmit" runat="server" Text="Log in" onClick="btnSubmit_Click"/>

    <p><asp:Label ID="lblResult" runat="server"></asp:Label></p>


In the following server-side code, Multi-Factor Authentication is configured and run in Step 2. Standard mode (MODE_STANDARD) is a telephone call to which the user responds by pressing the # key.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
    protected void Page_Load(object sender, EventArgs e)

    protected void btnSubmit_Click(object sender, EventArgs e)
        // Step 1: Validate the username and password
        if (username.Text != "Contoso" || password.Text != "password")
            lblResult.ForeColor = System.Drawing.Color.Red;
            lblResult.Text = "Username or password incorrect.";
            // Step 2: Perform multi-factor authentication

            // Add call details from the user database.
            PfAuthParams pfAuthParams = new PfAuthParams();
            pfAuthParams.Username = username.Text;
            pfAuthParams.Phone = "9134884271";
            pfAuthParams.Mode = pf_auth.MODE_STANDARD;
            // Specify a client certificate 
            // NOTE: This file contains the private key for the client
            // certificate. It must be stored with appropriate file 
            // permissions.
            pfAuthParams.CertFilePath = "c:\\cert_key.p12";

            // Perform phone-based authentication
            int callStatus;
            int errorId;

            if(pf_auth.pf_authenticate(pfAuthParams, out callStatus, out errorId))
                lblResult.ForeColor = System.Drawing.Color.Green;
                lblResult.Text = "Multi-Factor Authentication succeeded.";
                lblResult.ForeColor = System.Drawing.Color.Red;
                lblResult.Text = " Multi-Factor Authentication failed.";


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