Polarization encryption system using commercial LCDs for additive manufacturing

Polarization encryption has long been shown to allow simultaneous encryption of 2D images, but with scarce practical implementations or commercial applications to date. Nevertheless, a possible vector for its use in market products may be additive manufacturing (AM). As more complex and diversified technologies use AM in their production chains, intellectual property (IP) protection of shared data is becoming increasingly crucial. Many AM techniques rely on optical systems, therefore, it is essential to analyze the prospects of safeguarding AM processes using advances in optical secrecy. This work demonstrates the use of polarization encoding by employing liquid crystals for physical layer security. We examine the encoding of the information in a signal’s polarization state and show that linear transformations of polarization can be used to encrypt and decrypt data. We further demonstrate the use of off-the-shelf liquid crystal displays (LCD) in a low-cost commercial resin 3D printer to build a "polarization decryptor". The proposed system does not require any software modification and in hardware only the replacement of the printer’s LCD masking screen. This technique provides a promising methodology to secure part of the supply chain for AM operations.