In this book, I have introduced a novel two-factor data security protection mechanism for cloud storage system, in which a data sender is allowed to encrypt the data with knowledge of the individuality of a receiver only, while the receiver is necessary to use both his/her secret key and a security device to gain right to use to the data. Our solution not only enhances the confidentiality of the data but also offers the reliability of the device so that once the device is revoked; the corresponding cipher text will be restructured repeatedly by the cloud server lacking any notice of the data possessor. Furthermore, we accessible the security proof and efficiency analysis for our system. BIBLIOGRAPHY [1] A. Akavia, S. Goldwasser, and V. Vaikuntanathan, "Simultaneous hardcore bits and cryptography against memory attacks," in Proc. 6th Theory Cryptography Conf., 2009, pp. 474-495. [2] S. S. Al-Riyami and K. G. Paterson, "Certificateless public key cryptography," in Proc. 9th Int. Conf. Theory Appl. Cryptol., 2003, pp. 452-473.