Efficient Multi-receiver Certificate-Based Proxy Re-encryption Scheme for Secure Cloud Data Sharing

Sharing data through clouds has never been more economical and easier than now. To guarantee the confidentiality of the data stored in the cloud storages, the data owners should encrypt their sensitive data before uploading them to the clouds. But, traditional encryption paradigm makes it difficult for flexibly sharing encrypted data between different users. The paradigm of proxy re-encryption (PRE), which can securely delegate the decryption right from one user to another, offers an effective solution to the encrypted data sharing in the clouds. To share the encrypted data with multiple users efficiently and securely, we extend certificate-based PRE into the multi-receiver setting and put forward the notion of multi-receiver certificate-based PRE (MR-CBPRE). By using MR-CBPRE, a data owner can securely distribute his encrypted data to a group of users though public clouds in an efficient manner. We first formalize the syntax and security definition of MR-CBPRE, and then design a concrete MR-CBPRE scheme. In the random oracle model, the proposed scheme is proven to be chosen-ciphertext secure. To demonstrate the merits of our scheme, we analyze its performance by comparing it with the previous certificate-based PRE schemes which consist of only single receiver. As far as we know, it is the first certificate-based PRE scheme in the multi-receiver setting to date.