A cryptographic system includes: a) a light source for generating an excitation light signal; b) a spatial light modulator for encoding the excitation light signal with data; c) a wavelength dispersive element for transforming the excitation light signal into a spectral encoded light signal characterized by relative peak intensities at specific wavelengths; d) an optical detector for generating an information output signal in response to receiving an optical input signal, wherein the information output signal represents spectral and intensity characteristics of the optical input signal; and e) a processor for validating the information output signal if differences between representations of the optical input signal, and representations of the spectral encoded light signal are within predetermined limits.