Form Authentication for Mobile Applications

    November 21, 2003

In this example we will authenticate mobile web users for our application using Forms Authentication.

Other forms of authentication for mobile web applications are
– Windows Authentication
– Passport Authentication


When the user requests for a mobile web page from the application and if the user is not authenticated, the user is directed to the login page specified in the configuration settings. The user is prompted to enter the login and password. After the user is authenticated and authorized to access the page, the user is sent to the requested page (or the default page of the web site, if none is specifically requested). The user is now free to access the web site and navigate through the web site without being re-prompted for the login information.

When the user is done with the processing, he/she can Signout from the Application.
You can also specify a time-out period for the duration of time after which the validity of the login expires.

Since mobile pages may or may not support cookies, we enable cookieless operation.

Program Details

Step 1: Create the project:

Create a Visual C# Mobile Web Application in Visual Studio.Net.

Step 2: Create the login Mobile Web Page

Add a new Mobile Web Form to the project and name the page Login.aspx
Add the controls as shown in figure 1 below

Figure 1: Login.aspx

Change the following properties for controls added on the mobile web page:

Double click on the Command Control to start adding code to event handler for the onClick Event

Add the following code to the OnClick event handler of the Command control

if(FormsAuthentication.Authenticate(txtLogin.Text, txtPwd.Text))
FormsAuthentication.SetAuthCookie(txtLogin.Text, false);
lblError.Text = "Please check your credentials";

This is the code where the actual authentication occurs. If the user cannot be authenticated in the system, then we display and error message and prevent the user from proceeding in the site.

If the user is authenticated successfully, the user is directed to the requested page.

Add the following line of code to the top of the mobile web page.
using System.Web.Security;

Step 3: Create the other pages in the web site

We can now create the rest of the web site. Since this example is used to demonstrate forms authentication, our site will only contain two mobile web pages. Open the default web form that was created in the project “MobileWebForm1.aspx” and add a label control, a link control and a Command control. Change the properties of the control as shown in the table below

Rename the mobile web page “default.aspx”

Add the following code to the OnClick event handler of the Command control


Now add another Mobile Web Page in the project. Add a label and a link control on the mobile web form on this web page and set the following properties :

Step 4: Modify the configuration Settings

This is the main part where we specify that we opt for Forms Authentication

Add the following changes to the web.config file included in the project:

Delete the section for authentication in the existing file and add the following instead:

<authentication mode="Forms" >
<forms loginUrl="login.aspx" name=".COOKIEDEMO" timeout="60" path="/">
<credentials passwordFormat="SHA1">
<user name="user1"
password=" 5BAA61E4C9B93F3F0682250B6CF8331B7EE68FD8"/>
<user name="user2"
password=" 5BAA61E4C9B93F3F0682250B6CF8331B7EE68FD8"/>
<deny users="?" />

This section specifies the use of forms authentication and provides the passwords for the users using format “SHA1”. In this example the password for both the users is set to “password”. The trick in deriving the encoded value of password is making use of the function: FormsAuthentication.HashPasswordForStoringInConfigFile

We have also indicated in the <authorization> section that anonymous users must be denied access to all files in this application.

Replace the existing section for the SessionState with the following

<sessionState cookieless="true"/ >

Step 5: Build and Run the program and see the results

When you initially request for the mobile web page belonging to this application, you are not authenticated and hence, directed to the login page.

Figure 2: In the initial request, the user is not authenticated and therefore, directed to the Login Web page

Enter the following credentials:
Login: user1
Password: password

Note that the password text is not displayed to the user.

Click on the Login button and you will be sent to the requested web site if the correct credentials are entered.

Figure 3: User is authenticated successfully and redirected to the requested page.

After this the user will have access to the other web pages in the web site and won’t be prompted for login unless the Logout button is clicked or the validity of the login expires.

If the user clicks on the Logout button, he/she is logged out and redirected to the login page.

Figure 4: Incorrect Credentials – Note the error message


Security is a major concern for all applications, especially for Mobile Web Applications. We saw the use of FormsAuthentication in this example. Forms Authentication does not depend on IIS. You can build on this simple example and fortify your web site against invalid access.

*Originally published at CSharpCorner

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Dipal Choksi is a Bachelor of Engineering (Computer Science). She has industry experience in team-effort projects and also as an individual contributor. She has worked on Visual Basic, Visual C++, Java, Directory Services, ASP projects