Abstract: A new efficient identity-based group key distribution scheme that can dynamically determine the key distribution user-set is constructed. In the proposed scheme, each user obtains his decryption key based on his identity information from the key distribution center, and the bilinear mapping on Elliptic Curve is utilized to construct the broadcast encryption algorithm and decryption algorithm. The broadcast center only needs to broadcast a controlling header of less constant transmission size (three group elements), and the authorized users can recover the session key correctly from the broadcasting information. Both fully collusion-free security and dynamic joining for users are also implemented.

Key words: Group Communication, Broadcast Encryption, Bilinear Mapping, Public Key Infrastructure (PKI)