Experimental set-up The set-up consists of the spatial DOP modulator interfaced separately with the high-dimensional PNN and the encryption–decryption system. These two blocks make a different use of scattering media and digital neural networks and are described hereafter in dedicated subsections. The DOP modulator is composed of a phase-only liquid-crystal-on-silicon SLM (Hamamatsu X13138, 1,280 × 1,024 pixels, 12.5 μm
