The CONTRAIL approach to cloud federations.

The CONTRAIL project proposes a framework for Cloud Federations, that provides users with a single point of access to Cloud resources and relieves them from managing the credentials for access to individual Cloud service providers. The Federation services dynamically broker access to Cloud resources, ensures that the best available resource is selected, and that diverse resources are accessed consistently. This paper presents the CONTRAIL approach to federated identity management, focusing on authentication and authorization. In particular, we present "usage control" extensions to standard authorization frameworks to dynamically address changes in authorization decisions.