In this paper, the authors propose a decentralized access control mechanism using ABE (Attribute Based Encryption) and ABS (Attribute Based Signature) algorithm for anonymous authentication of data. Only valid user can perform decryption of data. This mechanism prevent replay attack and support creation, modification and reading data stored in a cloud. The proposed scheme is decentralized, robust and user privacy is the key requirement so that other users do not know the identity of the user. It should be ensured that users must not have the ability to access data even if they possess matching set of attributes. This method makes use of key policy attribute based encryption for security purpose.