Identity federation vs identity delegation

In the world of digital identity management, two terms that often come up are identity federation and identity delegation. While both concepts are crucial in ensuring secure and seamless access to resources across different systems, they represent distinct approaches to managing authentication and authorization.

In this article, we’ll explore what these terms mean, how they differ, and when to use them.

What is identity federation?

Identity federation (or federated identity—it’s the same thing) refers to the process of linking different systems together so that users can access these systems using a single set of credentials. Essentially, identity federation allows a user from one organization (or domain) to access applications or resources in another organization (or domain) without needing to create a new identity or login separately.

This is typically achieved through Single Sign-On (SSO) protocols like SAML (Security Assertion Markup Language), OAuth, or OpenID Connect. These protocols enable the exchange of identity information securely between federated identity providers (IdPs) and service providers (SPs), ensuring that users can authenticate once and gain access to multiple systems.

How identity federation works

1. First, users authenticate themselves with their identity provider. For example, if a user wants to access an app that uses Okta as the identity provider, they will be redirected to Okta to authenticate using their credentials (unless they are already logged in).
2. After successful authentication, an identity assertion (or token) is generated and sent to the app the user is trying to access.
3. The user can access applications or services in other federated domains (i.e., other apps) without needing to re-authenticate.

For example, a user with a Google account might be able to use that same account to log in to a third-party service like an online calendar app, leveraging Google's identity system as the federation model.

Benefits of identity federation

• Single Sign-On: Users can access multiple services without remembering different credentials.
• Reduced management overhead: Organizations do not have to manage user credentials across every service they partner with.
• Enhanced user experience: It streamlines the login process and reduces friction for users.

What is identity delegation?

Identity delegation, on the other hand, refers to the practice where one system (the delegator) allows another system (the delegate) to act on its behalf, typically in relation to authorization. In identity delegation, the delegator allows the delegate to access its resources or perform actions on its behalf based on a set of predefined permissions.

The most common example of identity delegation is OAuth—particularly OAuth 2.0. With OAuth, a user can grant a third-party application limited access to their resources (for example, their calendar or social media feed) without sharing their login credentials. Instead, they authenticate once and then delegate specific access to the third-party application, ensuring both security and control over the scope of access granted.

How identity delegation works

1. The user is asked to grant a third-party application access to specific resources. For example, if you use Todoist and want your to-dos to appear in your Google Calendar, Todoist will ask you to tell Google that you allow them to create new events on your behalf. To do so, they will redirect you to the delegator system (in this case, Google).
2. The user logs into the delegator system (e.g., Google, Facebook). After login, the delegator system presents the user with a list of permissions the delegate system asks for. In our example, Google will tell you that Todoist wants to be granted the permission to create new events in your calendar, and you have to say whether you agree or not.
3. Upon consent, the system issues an access token to the third-party application, allowing it to act on behalf of the user for a specific resource or operation.
4. The third-party app uses the token to access the delegated resource.

Benefits of identity delegation

• Granular control: Users can specify exactly what access the third-party application has (e.g., read-only vs. full access).
• Security: Delegation ensures that users’ credentials are not shared with third-party services, reducing the risk of credential theft.
• Flexible permissions: Delegation enables dynamic, fine-grained permissions, making it ideal for situations where a user needs to allow temporary or limited access.

Key Differences: identity federation vs. identity delegation

While both identity federation and identity delegation revolve around user authentication and access control, their purposes and mechanisms differ.

When to use each approach

Identity federation is ideal when:

• You need users to access multiple, independent applications or services without the need to log in repeatedly.
• You want a centralized identity management system where users authenticate once and access resources across multiple domains or organizations.
• Your organization is working with multiple partners or clients, and you want to streamline access control.

Identity delegation is ideal when:

• You need to allow third-party applications to access specific resources on a user's behalf without sharing sensitive credentials.
• Your application interacts with APIs and needs to securely request permission for accessing user data (like in social media, cloud storage, etc.).
• You want fine-grained control over what a third-party can do, specifying exactly what actions or data the third-party can access.

Can I use both identity federation and identity delegation?

Definitely yes. Identity federation and identity delegation serve different purposes and are typically used in complementary ways, depending on your use case.

You might use identity federation to authenticate a user and then delegate their identity (or permissions) to access other services on their behalf. For example, a user from a third-party organization (like an external IdP) logs into your system via SSO (identity federation), and once authenticated grants an application permission to access specific resources or perform actions on their behalf without having to re-authenticate or provide additional credentials (identity delegation).

In summary, these two can work together as long as they serve different purposes—federation for authentication and delegation for permissions to act on behalf of the user.

Conclusion

Identity federation and identity delegation serve different but equally important roles in modern identity management. Identity federation enables users to authenticate once and then access multiple services across separate systems, reducing the friction of repeated sign-ins. Meanwhile, identity delegation, typically implemented via OAuth 2.0, empowers external applications to act on a user’s behalf without ever revealing the user’s credentials.

Understanding the nuances of identity federation and identity delegation puts engineering teams in a stronger position to build robust, scalable systems that meet the evolving demands of modern, multi-domain environments.