Internet of Things security still remains a major concern. In the literature, the security approaches are subject to various limitations. For example, fingerprinting based on intrinsic properties is hampered by physical environmental phenomena and wireless channel’s dynamic. In this paper, a new security technique for message authentication in IoT is proposed. This proposed technique, based on Polarization Shift Keying, consists in using the polarization of the radio wave emitted by a device as a means of transmitting, in parallel with the main message, authentication data for this main message. Basically, this means cryptographically controlled modification of the polarization of the emitter outgoing wave. This is a kind of second modulation of the wave where the different used polarizations denote the symbols of this second modulation. Then, a security gateway is able to retrieve these symbols and recover the authentication code. This creates a secure communication link between the two terminals at the physical layer. The Polarization Shift Keying mechanism should not alter the original waveform and its primary modulation enough to increase the bit error rate. In this work, Polarization Shift Keying using two polarizations (Binary-PoSK) is experimented, along with different primary modulations. The results show that this technique could be a way of achieving secure communications in Internet of Things where devices are resource-constrained.