An Attribute-Based Anonymous Broadcast Encryption Scheme with Adaptive Security in the Standard Model

In broadcast encryption schemes, a distribution center broadcasts an encrypted message to a subset $S$ chosen from a universe of receivers and only the intended users are able to decrypt the message. Most broadcast encryption schemes do not provide anonymity and the identities of target receivers are sent in plaintext. However, in several applications, the authorized users\u27 identities has the same sensitivity as the message itself. YRL, is an anonymous attribute-based broadcast encryption scheme with linear computation, communication and storage overheads in the number of attributes. In this paper, we first propose an attack on the YRL scheme and show that unfortunately the unauthorized receivers can also decrypt the broadcasted message. Next, we propose the Improved-YRL scheme and prove that it achieves anonymity and semantic security under adaptive corruptions in the chosen ciphertext setting. The proof is provided using the dual system encryption technique and is based on three complexity assumptions in composite order bilinear maps. The Improved-YRL scheme is a step forward in solving the long-standing problem of secure and low overhead anonymous broadcast encryption