Abstract: Cloud offers resources to the users like hardware, software and allows users to access services from anywhere in the world at anytime through internet. Cloud also provides huge amount of space for the user to store their valuable data. Cloud users expect services from cloud service providers (CSP) in most of the time, so cloud providers should be always active. If a cloud service provider is failed due to some problem, then users canít access his/her data from cloud. This results in shifting the attention of the users from single cloud to multi-clouds. Even-though the cloud has many advantages, cloud users are still feeling insecure to use cloud. Security of the outsourced data to cloud is a major concern. This survey provides an in-sight on various multi-cloud security schemes which addresses some of the important security issues of cloud like integrity, confidentiality, service availability. The survey also provides the comparison of the schemes with respect to the issues they addressed.

Keywords: DNA Encryption, Trusted Third Party, CPDP, CSP, MCDB, VPC.