Identity-based broadcast encryption with recipient privacy

In many broadcast systems, it is important to protect both distributed content and the identities of authorized recipients. But many systems fail to protect the privacy of their users. In this paper, we propose the first identity-based broadcast encryption scheme with recipient privacy, enables the efficient encryption of messages to multiple recipients without revealing the identities of authorized recipients. In our scheme, the size of private keys is constant, the public key and ciphertexts are of size linear in the maximal size m of the set of authorized recipients, which is smaller than the number of possible users in the system. Finally we prove the security of our scheme by using the GDDHE framework.