Secure Identity-based Threshold Broadcast Encryption in the Standard Model

The general threshold broadcast encryption is not suitable for the networks with the constraints of computation and energy. In this paper, two constructions of the proper threshold broadcast encryption to these networks are proposed. In the proposed schemes, any user can dynamically join the system as a possible recipient, and the sender can dynamically choose the set of recipients S and the threshold value t. The new schemes achieve constant size private keys and O(n-t)-size ciphertexts. In addition, these schemes achieve full security in the standard model. Finally, we also show that they are provable security under n+1-Weak Decision Bilinear Diffie-Hellman Exponent (n+1wDBDHE) assumption and the static assumptions respectively.