Anonymous Certificate-Based Broadcast Encryption With Personalized Messages

Broadcast encryption with personalized messages (BEPM) is a newly proposed cryptographic primitive, which supports a broadcaster to deliver the common encrypted broadcast message to a group of authorized users. It also supports a broadcaster to deliver the personalized messages to the individual authorized users simultaneously. However, none of the existing BEPM schemes consider the anonymity of authorized users, which is a crucial security requirement for many BEPM application scenarios. Besides, the previous studies on BEPM only achieve security against chosen-plaintext attack adversaries. Certificate-based cryptosystem gives a viable way to construct more secure and efficient BEPM schemes. We propose the new concept of anonymous certificate-based broadcast encryption with personalized messages (ANON-CBBE-PM). Subsequently, we illustrate the formal definition and the security model of ANON-CBBE-PM. Furthermore, we present an ANON-CBBE-PM scheme, which solves key escrow problem in identity-based cryptosystem and certificate management problem in traditional public key cryptosystem. Compared with the existing BEPM schemes, the proposed scheme not only protects the privacy of authorized users, but also has advantage in performance. To be more specific, the lengths of the user secret key and the system public parameters, as well as the cost for decryption are constant. For those BEPM applications with a multitude of users whose computing ability is limited, the proposed scheme is more practical. In addition, our scheme simultaneously achieves anonymity and confidentiality under adaptive chosen-ciphertext attack in the standard model.