Cloud revocation authority using identity based encryption

Identity-based encryption (IBE) is a public key cryptosystem and eliminates the demands of public key infras structure (PKI) and certificate admiration in conventional public key settings .Due to the absence of PKI, the revocation problem is a critical issue in IBEs settings .Several revocable IBE schemes have been proposed regarding this issue. Quite recently, by embedding an outsourcing computation technique into IBE, Li et al. proposed a revocable IBE scheme with a key -update cloud service provider (KU-CSP). However, their scheme has two shortcomings. One is that the computation and communication costs are higher than previous revocable IBE schemes. The other shortcoming is lac k of scalability in the sense that the KU -CSP must keep a secret value for each user. In the article, we propose e a new revocable IBE scheme with a cloud revocation authority (CRA) to solve the two shortcomings, namely, the performance is significantly imp roved and the CRA holds only a system s secret for all the users. For security analysis is , we demonstrate that the proposed scheme is semantically secure under the decisional bilinear Diffie- Hellman (DBDH) assumption. Finally, we extend the proposed revocable IBE scheme to present a CRA -aided authentication scheme with period-limited privileges for managing a large number of various cloud services. We proposed a new revocable IBE scheme with a cloud revocation authority (CRA), in which the revocation procedure is performed by the CRA to alleviate the load of the PKG. This outsourcing computation technique with other authorities has been employed in Li et al.’s revocable IBE scheme with KU -CSP. Their scheme requires higher computational and communicational costs than previously proposed IBE schemes. For the time key update procedure, the KU-CSP in Li et al.’s scheme must keep a secret value for each user so that it is lack of scalability. In our revocable IBE scheme with CRA, the CRA holds only a master time key to perform the time key update procedures for all the users without affecting security