What are the various ways of authentication techniques in ASP.NET? Dot Net Interview Questions

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Selecting an authentication provider is as simple as making an entry in the web.config file for the application. 

You can use one of these entries to select the corresponding built in authentication provider:

 <authentication mode=”windows”>

 <authentication mode=”passport”>

 <authentication mode=”forms”>

 Custom authentication where you might install an ISAPI filter in IIS that compares incoming requests to list of source IP addresses, and considers requests to be authenticated if they come from an acceptable address. In that case, you would set the authentication mode to none to prevent any of the .net authentication providers from being triggered.

Windows authentication and IIS

If you select windows authentication for your ASP.NET application, you also have to configure authentication within IIS. This is because IIS provides Windows authentication. IIS gives you a choice for four different authentication methods:

Anonymous, basic digest and windows integrated

If you select anonymous authentication, IIS doesn’t perform any authentication, Any one is allowed to access the ASP.NET application. If you select basic authentication, users must provide a windows username and passwordto connect. How ever this information is sent over the network in clear text, which makes

basic authentication very much insecure over the internet.

If you select digest authentication, users must still provide a windows user name and password to connect. However the password is hashed before it is sent across the network. Digest authentication requires that all users be running Internet Explorer 5 or later and that windows accounts to stored in active directory. If you select windows integrated authentication, passwords never cross the network.Users must still have a username and password, but the application uses either the Kerberos or challenge/response protocols authenticate the user. Windows-integrated authentication requires that all users be running internet explorer 3.01 or later Kerberos is a network authentication protocol. It is designed to provide strong authentication for client/server applications by using secret-key cryptography. Kerberos is a solution to network security

problems. It provides the tools of authentication and strong cryptography over the network to help to secure information in systems across entire enterprise.

Passport authentication

Passport authentication lets you to use Microsoft’s passport service to authenticate users of your application. If your users have signed up with passport, and you configure the authentication mode of the application to the passport authentication, all authentication duties are off-loaded to the passport servers. Passport uses an encrypted cookie mechanism to indicate authenticated users. If users have already signed into passport when they visit your site, they’ll be considered authenticated by ASP.NET. Otherwise they’ll be redirected to the passport servers to login. When they are successfully log in, they’ll be redirected back to your site.

To use passport authentication you have to download the Passport Software Development Kit (SDK) and install it on your server. The SDK can be found at http://msdn.microsoft.com/library/default.asp url=/downloads/list/websrvpass.aps.It includes full details of implementing passport authentication in your own applications.

Forms authentication

Forms authentication provides you with a way to handle authentication using your own custom logic with in an ASP.NET application. The following applies if you choose forms authentication.

When a user requests a page for the application, ASP.NET checks for the presence of a special session cookie. If the cookie is present, ASP.NET assumes the user is authenticated and processes the request.

If the cookie isn’t present, ASP.NET redirects the user to a web form you provide. You can carry out whatever authentication, checks you like in your form. When the user is authenticated, you indicate this to ASP.NET by setting a property, which creates the special cookie to handle subsequent requests.