  Wave-based cryptography, at the vanguard of advancing technologies in
advanced information science, is essential for establishing a diverse array of
secure cryptographic platforms. The realization of these platforms hinges on
the intelligent application of multiplexing techniques, seamlessly combined
with appropriate metasurface technology. Nevertheless, existing multi-channel
encryption technologies based on metasurfaces face challenges related to
information leakage during partial channel decoding processes. In this paper,
we present a reprogrammable metasurface for polarization modulation. This
metasurface not only allows for the arbitrary customization of linearly
polarized reflected waves but also enables real-time amplitude modulation.
Here, relying on polarization amplitude control, a fully secure communication
protocol is developed precisely in the terahertz (THZ) spectrum to achieve
real-time information encryption based on polarization modulation metasurfaces
where access to information is highly restricted. The proposed metasurface
employs the double random phase encryption (DRPE) algorithm for information
encryption. It transmits the encrypted data through different polarization
channels using two graphene nanoribbons, exclusively controlled by external
biasing conditions. Various encryption scenarios have been outlined to fortify
information protection against potential eavesdroppers. The simulated results
show that this unique technology for hiding images by manipulating the
polarization of the reflected wave provides new opportunities for various
applications, including encryption, THz communications, THz secure data
storage, and imaging.
