Sammendrag
Cloud federation brings together different service providers and their offered services, so that many Cloud variants can be tailored to match different sets of customer requirements. To mitigate security risks and convince hesitant customers, security must be an integrated part of the federated Cloud concept. This paper surveys the state of the art in Cloud computing security, identifies unsolved issues related to federated Clouds, discusses possible approaches to deal with the threats and points out directions for further work.