IB Encryption ON Cloud Data Outsourcing computing by user Revocation

Abstract

Identity-Predicated Encryption (IBE) which simplifies the public key and certificate management at Public Key Infrastructure (PKI) is a consequential alternative to public key encryption. However, one of the main efficiency drawbacks of IBE is the overhead computation at Private Key Engenderer (PKG) during utilizer revocation. Efficient revocation has been well studied in traditional PKI setting, but the cumbersome management of certificates is precisely the encumbrance that IBE strives to alleviate. In this paper, aiming at tackling the critical issue of identity revocation, we introduce outsourcing computation into IBE for the first time and propose a revocable IBE scheme in the server-availed setting. Our scheme offloads most of the key generation cognate operations during key-issuing and key-update processes to a Key Update Cloud Accommodation Provider, leaving only a constant number of simple operations for PKG and users to perform locally. This goal is achieved by utilizing a novel collusion-resistant technique: we employ a hybrid private key for each utilizer, in which an AND gate is involved to connect and bound the identity component and the time component. Furthermore, we propose another construction which is provable secure under the recently formulized Refereed Delegation of Computation model. Conclusively, we provide extensive experimental results to demonstrate the efficiency of our proposed construction.