Identity-based authenticated broadcast encryption and distributed authenticated encryption

Since its introduction, broadcast encryption has attracted many useful applications. In this paper, we propose two identity-based schemes for authenticated broadcasting and distributed message authentication. The first scheme supports multiple broadcasters and allows each broadcaster to dynamically broadcast messages into an arbitrary group of receivers determined by the broadcaster. The receivers can obtain the broadcasted message using the identity of the broadcaster and his own secret decryption key; hence it ensures both confidentiality and authenticity of the message. The second scheme allows users (receivers) to send messages back to the broadcaster where the authentication of messages is done with the identity of the user. We also provide security proofs for our schemes under the random oracle model.