CISSP: Certified Information Systems Security Professional

Federated identity management uses two main trust models: cross-certification and the trusted third party (TTP) model. In cross-certification each organization must individually review and trust every other member, which creates an unmanageable web of pairwise trust relationships once you scale to dozens of participants. The trusted third party (bridge/broker) model has every organization establish trust with a single central authority instead of with each other, so it scales cleanly across large federations. Therefore, for a network among dozens of organizations, the trusted third party is the major component used. IDaaS (A) is a delivery/hosting option and ABAC (B) is an access-control model, neither of which is the FIM trust-establishment component in question.