International Journal of Computer Science and Mobile Computing (IJCSMC)
Cloud computing can provide infinite computing resources on demand due to its high scalability in nature, which eliminates the needs for Cloud service providers to plan far ahead on hardware provisioning. Security is the biggest challenge to promote cloud computing currently. Trust has proved to be one of the most important and effective alternative means to construct security in distributed systems. Multi located data storage and services in the Cloud make privacy issues even worse. In order to efficiently and safely construct entities trust relationship in cloud and cross-clouds environment, identity management services are crucial in cloud computing infrastructures to authenticate users and to support flexible access control to services, based on user identity properties (also called attributes) and past interaction histories.