Design and Formal Verification of DZMBE+

In this paper, a new broadcast encryption scheme is presented based on threshold secret sharing and secure multiparty computation. This scheme is maintained to be dynamic in that a broadcaster can broadcast a message to any of the dynamic groups of users in the system and it is also fair in the sense that no cheater is able to gain an unfair advantage over other users. Another important feature of our scheme is collusion resistance. Using secure multiparty computation, a traitor needs k cooperators in order to create a decryption machine. The broadcaster can choose the value of k as he decides to make a trade-off between communication complexity and collusion resistance. Comparison with other Broadcast Encryption schemes indicates enhanced performance and complexity on the part of the proposed scheme (in terms of message encryption and decryption, key storage requirements, and ciphertext size) relative to similar schemes. In addition, the scheme is modeled using applied pi calculus and its security is verified by means of an automated verification tool, i.e., ProVerif.