0Abstract: Cloud computing delivers IT resources as a Service over Internet. The advantage of cloud computing is everlasting but it brings more issues including security. Ensuring the security of cloud computing is a foremost factor in the cloud computing environment, as users often store sensitive data with cloud storage providers but these providers may be untrusted. Cloud storage providers may be single cloud or multi-cloud. But it is found that the research into the use of multi-clouds providers to maintain security has received less attention from the research community than the use of single clouds. In this paper, we have created a framework to supply a secure cloud database that will guarantee to prevent security risks facing the cloud computing community. This framework applied multi-clouds and the date constraint validation to reduce the risk of data intrusion and the loss of service availability in the cloud and ensure data integrity. We present a virtual storage cloud system called DepSky which consists of combination of different clouds to build a cloud of cloud. Keywords : Cloud computing, cloud storage, data integrity, data intrusion, multi-clouds, service availability single cloud.
