Date Added: Dec 2010
Cloud computing offers an appealing business model and it is tempting for companies to delegate their IT services to the cloud. Yet, a company might find it risky to do so for sensible services and to depend entirely on a single provider, which can be vulnerable and constitute a clearly identified target for attackers. The authors explore in this paper a replication approach where copies of the same IT service are placed on several (Cumulus) clouds that are not only independent but actually unaware of each other. Replica consistency is ensured using CBFT, a new BFT protocol designed for wide area networks.