Efficient public-key authenticated deniable encryption schemes

The notion of deniable encryption (DE) was introduced to achieve secret communications in situations of coercion or bribery. Generally, it allows a user to open the same ciphertext into multiple different messages. After the initial constructions, numerous DE schemes have been proposed to improve efficiency. Whereas, all existing DE schemes under the fully deniable framework are still inefficient due to the huge communication and computation overhead. Furthermore, these DE schemes also do not provide the functionality of authentication of users (include senders and receivers), which is a necessary functionality for various application scenarios. For instance, in the setting of electronic voting, if the voting center cannot correctly verify the identities and eligibility of voters, double voting and voter impersonation cannot be prevented. This will affect the final result of the voting and destroy the fairness of the election. Moreover, due to the existence of trust problems, voters also need to confirm whether the voting center is a genuine and legal institution. In this paper, we first formalize the syntax and security notions of public-key authenticated deniable encryption, and then propose two concrete constructions under the fully deniable framework. We also prove that our DE constructions are provably secure in the random oracle model. When comparing with available DE schemes, the proposed DE ones not only provide the desired functionality of mutual authentication, but also enjoy high efficiency. Therefore, they are more suitable for practical applications.