A new outsourcing conditional proxy re-encryption suitable for mobile cloud environment

The mobile cloud is a highly heterogenous and constantly evolving network of numerous portable devices utilizing the powerful back-end cloud infrastructure to overcome their severe deficiency in computing resource and offer various services such as data sharing. Inherently, in mobile cloud, the risk of user privacy invasion by the cloud operator is high. The conditional proxy re-encryption (CPRE) is a useful concept for secure group data sharing via cloud while preserving the privacy of the shared data from any unintended third parties including the cloud operator. Unfortunately, the state-of-art CPRE is not particularly designed for mobile cloud environment and therefore imposes heavy burdens to the weak mobile cloud clients. This paper introduces a new CPRE scheme, namely the CPRE for mobile cloud, which utilizes the back-end cloud to the extreme extent so that the overhead of terminals is drastically reduced. Specifically, our scheme outsources a significant amount of computation overhead caused by the following functions at terminals: (a) re-encryption key generation, (b) condition value change, and (c) decryption, to the cloud. The proposed scheme also allows users to verify the correctness of outsourced computation under refereed delegation of computation model. Our simulation results show CPRE for mobile cloud that outperforms its existing alternatives.