The use of cloud computing has increased rapidly in many organizations. Cloud computing provides many benefits in terms of low cost and accessibility of data. Ensuring the security of cloud computing is a major factor in the cloud computing environment, as users often store sensitive information with cloud storage providers but these providers may be untrusted. Dealing with \"Single cloud\" providers is predicted to become less popular with customers due to risks of service availability failure and the possibility of malicious insiders in the single cloud. A movement towards \"Multi-clouds\", or in other words, \"Inter-clouds\" or \"Cloud-of-clouds\" has emerged recently. The increasing popularity of cloud storage services has lead companies that handle critical data to think about using these services for their storage needs.