FIM provides a way to connect the identity management system when user information is stored in the third-party identity provider (IdP). With FIM, the user only provides authentication information to the IdP, which in turn already has a trusted relationship with the service.
As illustrated in the following diagram, when a user logs in to access a service, the service provider (SP) gets credentials from the IdP, rather than getting them directly from the user:
SSO allows the use of a single sign-on, with which the user can access multiple services. Here, an SP could target an environment where you want to log in—for example, a Customer Relationship Management (CRM) application or your cloud application. An IdP could be a corporate AD. Federation allows something similar to an SSO without a password, as the federation server knows users to access information.
There are various techniques available to implement FIM and SSO. Let's look at some of the popular...