Robust Deniable Authentication Protocol

Deniable authentication protocol is a new technique of modern cryptography. The protocol not only enables an intended receiver to identify the source of a received message, but also prevents a third party from identifying the source of the message. Recently, Shao et al. pointed out that Wang et al.’s deniable authentication protocol based on ElGamal cryptosystem is insecure to a person-in-the-middle attack; that is, in the whole process, the receiver cannot be aware of the existence of this adversary as well as the modification of the messages. Furthermore, they also presented a modification of Wang et al.’s protocol to overcome the security flaw. However, this paper demonstrates that Shao et al.’s improved protocol is still susceptible to a malicious receiver’s impersonation attack. To mitigate this security breach, we propose a robust deniable authentication protocol based on ElGamal cryptography.