Single Sign-On, or SSO, is a method for digital authentication that allows users to use one set of login credentials, such as a username and password, to access multiple applications. This simplifies the user's management of their identity and credentials, making it easier for them to access the services they need without having to remember multiple passwords.

SSO authentication is not a new concept; it has been used in various forms for several years. However, with the rapid growth of mobile applications and the increasing need for seamless integration across multiple services, the importance and relevance of SSO have grown significantly.

The primary purpose of SSO is to link all of a user's applications to a single authentication source. This means that once a user is authenticated by this central source, they can access all of their applications without needing to log in again.

The Need for SSO in Mobile Applications 

  1. Enhanced User Experience

By implementing SSO, mobile applications can streamline the login process, making it quicker and easier for users to access their services. This not only improves the user experience but also increases the likelihood of users returning to the application, contributing to higher user retention rates.

In addition to simplifying the login process, SSO also reduces the risk of users forgetting their passwords and being locked out of their accounts. This, in turn, can reduce the number of support requests related to password recovery, saving both the user and the application provider time and effort.

  1. Improved Security

By reducing the number of passwords that a user needs to remember, SSO decreases the likelihood of users resorting to insecure practices, such as using weak passwords or reusing the same password across multiple applications.

SSO providers usually implement robust security measures, such as multi-factor authentication and anomaly detection, to ensure that the user's credentials are secure. This adds an additional layer of security to the mobile applications that use SSO, helping to protect both the user's data and the integrity of the application itself.

  1. Seamless Integration Across Services

Another significant benefit of SSO for mobile applications is its ability to provide seamless integration across multiple services. With SSO, users can switch between different applications or services without the need to authenticate each time, creating a more unified and efficient user experience.

This is particularly beneficial for businesses that offer multiple services or applications to their users. With SSO, they can provide their users with a seamless experience across all of their offerings, enhancing user satisfaction and loyalty.

Furthermore, SSO can also facilitate inter-application communication and data sharing. This means that data can be shared securely between different applications, allowing for more personalized and context-relevant services.

How SSO Works in Mobile Applications 

  1. Authentication Process

The process begins when a user attempts to access an application that uses SSO. The application then redirects the user to the SSO provider's authentication page.

The user enters their credentials, and the SSO provider verifies them. If the credentials are valid, the SSO provider sends a token back to the application. This token serves as proof that the user has been authenticated.

Once the application receives this token, it allows the user to access its services. The user can then access any other applications that use the same SSO provider without needing to re-authenticate, as long as their session is still active.

  1. Token-Based Authentication

When a user authenticates with an SSO provider, they receive a token, not a password. This token is then used to authenticate the user with all of their applications.

Tokens are secure, unique identifiers that are issued for a specific user and a specific session. They are typically encrypted and can include additional information, such as the user's identity and the time the token was issued.

Because tokens are unique to each session, they provide a secure way of authenticating users without the need for them to enter their credentials each time they access an application. This makes them an ideal solution for SSO in mobile applications.

  1. Role of Identity Providers (IdP)

Identity Providers, or IdPs, play a crucial role in SSO for mobile applications. An IdP is a service that creates, maintains, and manages identity information for principals and provides principal authentication to other services within a federation.

In the context of SSO, the IdP is responsible for verifying the user's credentials and issuing the authentication token. The IdP also maintains the user's session, allowing them to access multiple applications without needing to re-authenticate.

By centralizing the authentication process, IdPs not only simplify the user's experience but also improve the security and integrity of the authentication process. This makes them a critical component of any SSO solution for mobile applications.

Example of an SSO Implementation

To implement SSO in a mobile application, developers can use OAuth 2.0, a widely-adopted protocol for authorization. OAuth 2.0 allows users to grant a mobile app access to their information stored in another service without exposing their credentials. For instance, a mobile app can enable users to log in using their Google or Facebook account credentials.

To achieve this, developers might use specific libraries and SDKs provided by the platform (e.g., Google Sign-In for Android, Facebook SDK for iOS) or general-purpose libraries like AppAuth for both Android and iOS. These libraries manage the complex aspects of OAuth 2.0, such as handling tokens and securely managing user sessions.

Below is a simplified overview of implementing Google Sign-In for an Android mobile application using OAuth 2.0. The specifics can vary depending on the app’s requirements and the chosen technology stack. 

  1. Setting up the Development Environment

Include the Google Sign-In dependency in the app's build.gradle file (in the dependencies section): 

implementation 'com.google.android.gms:play-services-auth:xx.x.x'.

Then, use the Google API Console to obtain the OAuth 2.0 client ID.

  1. Integrating the Sign-In Button

Include the Google Sign-In button in the app’s layout XML. In the activity code, initialize GoogleSignInOptions with the DEFAULT_SIGN_IN parameter and the client ID. 

<RelativeLayout

    xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent">

    <!-- Other UI elements -->

    <com.google.android.gms.common.SignInButton

        android:id="@+id/sign_in_button"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_centerInParent="true"/>

</RelativeLayout>

Create a GoogleSignInClient object using the method: 

GoogleSignIn.getClient(this, googleSignInOptions)

  1. Handling Sign-In Intent

When the sign-in button is clicked, trigger an intent to display the Google sign-in form using this method:

startActivityForResult(googleSignInClient.getSignInIntent(), RC_SIGN_IN)

Override onActivityResult to handle the sign-in result. If the result is successful, use GoogleSignIn.getSignedInAccountFromIntent to get the GoogleSignInAccount object.

  1. Retrieving the Auth Token and Maintaining User Session

Use GoogleSignInAccount.getIdToken() to retrieve the OAuth 2.0 token. Then, send this token to the server to create a session or validate the user.

Upon successful authentication, store the user’s account information securely (preferably using encrypted shared preferences or a secure server). Check for an existing user session in the onCreate method of the main activity. If a session exists, bypass the login screen and direct the user to the main content of the app.

Conclusion

In conclusion, Single Sign-On (SSO) for mobile applications allows users to access multiple applications with a single set of credentials, SSO simplifies the login process, enhances user experience, and significantly boosts security. It mitigates common issues like password fatigue and insecure password practices, while also facilitating seamless inter-app communication and data sharing.

We showed a simple example of how to integrate SSO into a mobile application using OAuth 2.0 and Google Sign-In for Android. This shows how easy it can be to provide a more unified and efficient authentication experience for modern mobile applications.