Identity federation is a key factor for a user to access multiple service providers seamlessly. Many protocols that federate between the providers have been proposed. Such protocols are operated under the same rules of identity management between the federated providers. Moreover, cross-protocol federation that uses different protocols for federation between the providers has also been proposed. However, the providers cannot federate all user information even though they do so using the cross-protocol federation because they do not confirm whether the federated providers obey the same rules or not. A federation bridge that converts and regulates the interaction messages between the providers is described herein. With it, the provider can federate based on the rules that a user and the providers determine.