Decentralized access control scheme for secure data storage in clouds, which supports anonymous authentication. In the proposed scheme, the cloud verifies the authenticity of the being without knowing the identity of the user before storing data. Our schema also has the additional feature of access control in which only valid users are able to decrypt the stored information. The scheme avoids repetitive attacks and supports the creation, modification and reading of data stored in the cloud. We also handle revocation of users. In addition, our authentication and access control scheme is decentralized and robust, unlike other access control schemes designed for clouds that are centralized.