Cloud Computing is an information technology type which is used to access information and sharing of data on remote site. By using cloud computing one has not to worry about load of local data storage to store his data. Security And authentication of data is must while using this kind of services. Various factors are presents there which can affect security of data. This paper provide an idea about security and authentication operation .This paper explain some encryption scheme as well as RSA and how to improve security of a data using Symmetric Tokens. This paper proposes a multilevel authentication technique that helps us to enhance the security of data storage in the cloud computing systems. We provide combined approach DES and AES using RSA to protect clients' authentication data such as user name and password.