Islamic Azad University
Cloud computing is an expression which is used by IT server companies to exchange computing needs as an asymmetrical service of relation for the final receivers of these services. All the models of the cloud computing depend on the resource sharing on the network due to regarding access integrity economic scale. Generally, in most technologies related to the IT, the most important challenge is security. It is particularly more emphasized in cloud computing as the inaccessible control of the final user data cause that the user needs more assure to use and accept this technology. In this paper, a lot of efforts are done from service providers (servers), scientific association and so on in facilitating security issues.