Effect of random phase mask on input plane in photorefractive authentic memory with two-wave encryption method

Akifumi Mita; Atsushi Okamoto; Hisatoshi Funakoshi

doi:10.1117/12.528717

17 June 2004 Effect of random phase mask on input plane in photorefractive authentic memory with two-wave encryption method

Akifumi Mita, Atsushi Okamoto, Hisatoshi Funakoshi

Author Affiliations +

Proceedings Volume 5362, Advanced Optical and Quantum Memories and Computing; (2004) https://doi.org/10.1117/12.528717
Event: Integrated Optoelectronic Devices 2004, 2004, San Jose, CA, United States

Abstract

We have proposed an all-optical authentic memory with the two-wave encryption method. In the recording process, the image data are encrypted to a white noise by the random phase masks added on the input beam with the image data and the reference beam. Only reading beam with the phase-conjugated distribution of the reference beam can decrypt the encrypted data. If the encrypted data are read out with an incorrect phase distribution, the output data are transformed into a white noise. Moreover, during read out, reconstructions of the encrypted data interfere destructively resulting in zero intensity. Therefore our memory has a merit that we can detect unlawful accesses easily by measuring the output beam intensity. In our encryption method, the random phase mask on the input plane plays important roles in transforming the input image into a white noise and prohibiting to decrypt a white noise to the input image by the blind deconvolution method. Without this mask, when unauthorized users observe the output beam by using CCD in the readout with the plane wave, the completely same intensity distribution as that of Fourier transform of the input image is obtained. Therefore the encrypted image will be decrypted easily by using the blind deconvolution method. However in using this mask, even if unauthorized users observe the output beam using the same method, the encrypted image cannot be decrypted because the observed intensity distribution is dispersed at random by this mask. Thus it can be said the robustness is increased by this mask. In this report, we compare two correlation coefficients, which represents the degree of a white noise of the output image, between the output image and the input image in using this mask or not. We show that the robustness of this encryption method is increased as the correlation coefficient is improved from 0.3 to 0.1 by using this mask.

Citation Download Citation

Akifumi Mita, Atsushi Okamoto, and Hisatoshi Funakoshi "Effect of random phase mask on input plane in photorefractive authentic memory with two-wave encryption method", Proc. SPIE 5362, Advanced Optical and Quantum Memories and Computing, (17 June 2004); https://doi.org/10.1117/12.528717

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