Cloud computing is evolved from the development of parallel computing, distributed computing and grid computing. It's been one amongst the foremost hot analysis topics. Trust and security are the highest considerations of cloud computing users. These are terribly important in the rising field of cloud computing. Owing to several new problems surfaced from cloud computing promise of elasticity and availability, the existing techniques used for the privacy and security might not completely resolve cloud computing security issues. A number of new constraints embodied are definition of data ownership, virtualization, multi-tenancy, elasticity and cross-geographical server environments.