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Optical Image encryption based on apertured FrMT in the Diffraction domain

Abstract : This thesis focuses on the study of introducing the aperture into FrMT in diffraction domain (FrMT) and its application in optical image encryption system. The feasibility of the proposed encryption schemes is verified by a series of numerical simulations. The main work is as follows:Firstly, an optical image encryption scheme based on the fractional Mellin transform with a hard aperture has been proposed. The apertured fractional Mellin transform (apertured FrMT) can be performed through the log-polar transform and the apertured fractional Fourier transform in diffraction domain. The side-lengths of the hard aperture serve as a key to improve the security and further increase the key space of the encryption system. This hard aperture is not only used to control the amount of light passing the lens by adjusting its size, but also reduces the leakage of light, which will, to some extent, enhance the robustness against direct attacks.Secondly, the Gaussian aperture, as a soft aperture for balancing between hard aperture and no aperture, is introduced into the apertured FrMT. With the Gaussian apertured FrMT in diffraction domain, a reality-preserving transform is proposed and used for image encryption. In this encryption scheme, for gray image, the Arnold transform and the bitwise XOR operation are also adopted to encrypt the image in order to enhance the security.Finally, the encryption algorithm based on Gaussian apertured reality-preserving FrMT (GARPFrMT) used for color image is proposed. Besides, nonlinear GARPFrMT, color space rotation, together with 3D scrambling and bitwise XOR operation make the proposed color image encryption algorithm have good performance.The simulation results have shown that the proposed encryption schemes are capable of resisting different common attacks and robust against noise and occlusion attacks.
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Submitted on : Tuesday, April 7, 2020 - 12:07:13 PM
Last modification on : Wednesday, April 8, 2020 - 1:43:52 AM

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  • HAL Id : tel-02534903, version 1

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Mengmeng Wang. Optical Image encryption based on apertured FrMT in the Diffraction domain. Cryptography and Security [cs.CR]. Université de Poitiers; Nanchang University (Nanchang, Jiangxi, China), 2019. English. ⟨NNT : 2019POIT2326⟩. ⟨tel-02534903⟩

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