Today's people are moving towards the internet services through cloud computing to acquire their required service, but they have less confidence about cloud computing because all the tasks are handled by the service provider. Cloud system provides features to the owner to store their data on some remote locations and allow only authorized users to access their data according to their access capability. Data security becomes particularly serious in the cloud computing environment because data are scattered in different machines and storage devices including servers, PCs, and various mobile devices such as smart phones. To make the cloud computing be adopted by enterprise, the security concerns of users should be rectified first to make cloud environment trustworthy. The trustworthy environment is the basic prerequisite to win the confidence of users to adopt this technology. However, there are various security concerns that need to be taken care of regarding the trust maintenance between various parties, authorized access of confidential data, data storage privacy, and integrity.