Optical encryption in the axial domain using beams with arbitrary polarization

•Input polarization affects the performance of encryption in the focal area.•The energy of the longitudinal component influences photon counting encryption.•The most suitable polarization for encryption in the longitudinal domain is proposed.

Recently, a cryptosystem based on the analysis of light in the focal area of a high numerical aperture system has been proposed. A key element in the design of this device is the selection of the polarization of the input beam. In this paper we analyze how polarization influences the performance of the encoded message. In order to avoid attacks and enhance security, the system is assumed to work in photon-counting illumination conditions.