Cloud storage enables users to remotely store their data and enjoy the on-demand high quality cloud applications without the burden of local hardware and software management. Though the benefits are clear, such a service is also relinquishing users’ physical possession of their outsourced data, which inevitably poses new security risks towards the correctness of the data in cloud. In order to address this new problem and further achieve a secure and dependable cloud storage service, key management and key sharing plays the main role in the data sharing concept of cloud computing. Aggregate key cryptosystem is a concept in which key is generated by means of various attributes of data in various cipher text classes and its associated keys. Aggregate key consist of various derivations of identity and attribute based classes of respective data owner of cloud. Irrespective of traditional cryptographic key generation and derivations, this technique possesses complex, unique and robust cryptographic key aggregate cryptosystem which is optimal for secure cloud and privacy preserving key generation process.