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26 September 2013 Optical asymmetric cryptosystem using polarized light
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We propose an asymmetric image encryption and decryption scheme based on phase-truncated Fourier transform and polarization encoding. An image bonded with a random phase mask is Fourier transformed and the obtained spectrum is amplitude- and phase-truncated. The phase-truncated value is encrypted using the polarized light in which two independent optical plane waves are used. The first plane wave illuminates the input image and is encoded into a given state of polarization. The second plane wave illuminates an intensity key image and is encoded into another state of polarization. Thus obtained two waves are mixed to obtain first level of encryption. The resultant is then passed through a linear polarizer (pixilated polarizer), to obtain the second level of encryption. For decryption, encrypted image is passed through the pixilated polarizer rotated at appropriate angles. Finally, decrypted image is obtained by computing inverse Fourier transform of retrieved phase-truncated value bonded with amplitude-truncated value. The proposed method offers flexibility in the encryption key design. We also checked immunity against special attack if polarization keys are unknown. Due to amplitude- and phase-truncation process the designed keys are asymmetric in nature. Results of numerical simulation are presented in support of the encryption scheme.
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Sudheesh K. Rajput and Naveen K Nishchal "Optical asymmetric cryptosystem using polarized light", Proc. SPIE 8855, Optics and Photonics for Information Processing VII, 885503 (26 September 2013);


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