Considering the limitations of the IoT security solutions proposed in the literature, e.g., fingerprinting based on intrinsic properties is hampered by physical environmental phenomena and wireless channel's dynamic, a new security technique for message authentication in IoT is proposed in this paper. This 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. After promising results with linear polarizations, this paper presents a proof-of-concept on the use of circular polarizations to perform Polarization Shift Keying.