Attribute-Based Proxy Re-encryption with Dynamic Membership

Cloud computing has been developed rapidly in recent years, and offers novel concepts and innovations in computer use. The applications of cloud computing are that people can put their data on cloud and also can designate a proxy to help them to execute a number of tasks in certain situations. The proxy re-encryption which is a cryptographic primitive has been proposed to solve this problem. In the proxy re-encryption system, when a user (e.g., Alice) wants to send a cipher text that is encrypted by her public key and stored in the cloud to another user (e.g., Bob), she can designate a proxy to transform the cipher text into a different cipher text that can be decrypted by Bob´s private key. Recently, Fan et al. Proposed an attribute-based encryption scheme with dynamic membership. However, we found that their scheme may be flawed. In this paper we will modify Fan et al.´s scheme to fix the flaw. Based on our modified scheme and the proxy re-encryption, we also propose an attribute-based proxy re-encryption under bilinear pairing. Furthermore, the proposed scheme has rich access policies and dynamic membership.