Covert Authentication at the Physical Layer

The open nature of wireless communication makes it facing variable interferences, the one by malicious attackers can be more harmful since they can choose worthful messages to interfere for benefit maximization. Such targeted messages generally require comprehensive protection by variable security mechanisms, which improve security in some sense as well as the risk of being selective attacked. One is the authentication mechanism that guarantees authenticity but suffers from length detection since the common authentication is conducted by appending digital signature bits to message. Due to this disadvantage, in this paper, we consider embedding the digital signature into the message at the physical layer, which is difficult to be sensed by attackers. Unlike the previous radio frequency (RF) watermark technique that adds low-power authentication tag symbols to base message symbols, while performing obvious constellation characteristics that still can be detected, to make the authentication tag non-perceptible to attackers, we propose to use Trellis coded modulation (TCM) in the embedding process to prevent constellation characteristics based detection. The accuracy of such an authentication scheme and its effect on the based messages are demonstrated by simulations. Simulation results show that the proposed method can greatly provide covert authentication while satisfying good authentication accuracy.