Cloud computing is a highly scalable distributing computing platform in which resources are offered as services. The security of data in cloud is one of the important issues which act as an obstacle in the implementation of cloud computing. This paper is proposing an efficient cloud security model in which the model is providing the multi-level encryption mechanism over the data to be uploaded at the cloud as well as role-based authentication for the users. The model is including four parties: Data owner, Private Cloud, Admin and User. The encryption mechanism is using the RSA algorithm first and further re-encrypts the data with MD5 to enhance the security of the data. The Message authentication Code is being generated before uploading the encrypted data which will be used after downloading of the data. The Message Authentication Code of downloaded data will be decrypted first by user and then send to Data owner for data integrity check. After that the user can decrypt the downloaded data if he gets confirmation from Data owner. The model is using the best possible multiple techniques in a single approach.