Security of the conventional Fourier-based double-random-phase encryption (DRPE) technique is prone to impulse attacks, as the Fourier transform (FT) of a delta function results in a unity function. To negate such an attack, the phase factors of the lenses are modified by multiplying these with random-phase functions. Owing to this modification of the FT as a result of the randomized lens phase function, a modified FT (MFT~(LR)) gives the random output for a delta function input. Employing MFT~(LR) in the DRPE technique enhances the security features and makes the encryption system safer from the impulse attack. Numerical and experimental results are given for the validation of the proposed technique.
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