Image encryption system based on a nonlinear joint transform correlator for the simultaneous authentication of two users

We propose a new encryption system based on a nonlinear joint transform correlator (JTC) using the information of two biometrics (one digital fingerprint for each user) as security keys of the encryption system. In order to perform the decryption and authentication in a proper way, it is necessary to have the two digital fingerprints from the respective users whose simultaneous authentication is pursued. The proposed security system is developed in the Fourier domain. The nonlinearity of the JTC along with the five security keys given by the three random phase masks and the two digital fingerprints of the two users allow an increase of the system security against brute force and plaintext attacks. The feasibility and validity of this proposal is demonstrated using digital fingerprints as biometrics in numerical experiments.Peer ReviewedPostprint (published version

Effects of using an encrypted image corrupted by noise and occlusion in a security system based on joint transform correlator and Gyrator transform

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Image quality and security through nonlinear joint transform encryption

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Nonlinear encryption for multiple images based on a joint transform correlator and the Gyrator transform

A novel nonlinear encryption–decryption system based on a joint transform correlator (JTC) and the Gyrator transform (GT) for the simultaneous encryption and decryption of multiple images in grayscale is proposed. This security system features a high level of security for the single real-valued encrypted image and a high image quality for the multiple decrypted images. The multispectral or color images are considered as a special case, taking each color component as a grayscale image. All multiple grayscale images (original images) to encrypt are encoded in phase and placed in the input plane of the JTC at the same time without overlapping. We introduce two random-phase masks (RPMs) keys for each image to encrypt at the input plane of the JTC-based encryption system. The total number of the RPM keys is given by the double of the total number of the grayscale images to be encrypted. The use of several RPMs as keys improves the security of the encrypted image. The joint Gyrator power distribution (JGPD) is the intensity of the GT of the input plane of the JTC. We obtain only a single real-valued encrypted image with a high level of security for all the multiple grayscale images to encrypt by introducing two new suitable nonlinear modifications on the JGPD. The security keys are given by the RPMs and the rotation angle of the GT. The decryption system is implemented by two successive GTs applied to the encrypted image and the security keys given by the RPMs and considering the rotation angle of the GT. We can simultaneously retrieve the various information of the original images at the output plane of the decryption system when all the security keys are correct. Another result due to the appropriate definition of the two nonlinear operations applied on the JGPD is the retrieval of the multiple decrypted images with a high image quality. The numerical simulations are computed with the purpose of demonstrating the validity and performance of the novel encryption–decryption system.This research has been funded by the Universidad de La Guajira (Riohacha), the Universidad Popular del Cesar (Valledupar) and the Universitat Politècnica de Catalunya · BarcelonaTech, SGR 2021 SGR 00388 and the Agencia Estatal de Investigación, Spanish Government (PID2020- 114582RB-I00/AEI/10.13039/501100011033).Peer ReviewedPostprint (published version

Double image encryption system using a nonlinear joint transform correlator in the Fourier domain

In this work, we present a new nonlinear joint transform correlator (JTC) architecture in the Fourier domain (FD) for the encryption and decryption of two simultaneous images. The main features of the proposed system are its increased level of security, the obtention of a single real-valued encrypted signal that contains the ciphered information of the two primary images and, additionally, a high image quality for the two final decrypted signals. The two images to be encrypted can be either related to each other, or independent signals. The encryption system is based on the double random phase encoding (DRPE), which is implemented by using a nonlinear JTC in the FD. The input plane of the JTC has four non-overlapping data distributions placed side-by-side with no blank spaces between them. The four data distributions are phase-only functions defined by the two images to encrypt and four random phase masks (RPMs). The joint power spectrum (JPS) is produced by the intensity of the Fourier transform (FT) of the input plane of the JTC. One of the main novelties of the proposal consists of the determination of the appropriate two nonlinear operations that modify the JPS distribution with a twofold purpose: to obtain a single real-valued encrypted image with a high level of security and to improve the quality of the decrypted images. The security keys of the encryption system are represented by the four RPMs, which are all necessary for a satisfactory decryption. The decryption system is implemented using a 4f-processor where the encrypted image and the security keys given by the four RPMs are introduced in the proper plane of the processor. The double image encryption system based on a nonlinear JTC in the FD increases the security of the system because there is a larger key space, and we can simultaneously validate two independent information signals (original images to encrypt) in comparison to previous similar proposals. The feasibility and performance of the proposed double image encryption and decryption system based on a nonlinear JTC are validated through computational simulations. Finally, we additionally comment on the proposed security system resistance against different attacks based on brute force, plaintext and deep learning.This research has been funded by the Universidad de La Guajira (Riohacha), the Universidad Popular del Cesar (Valledupar) and the Universitat Politècnica de Catalunya · BarcelonaTech.Peer ReviewedPostprint (published version

Occlusion and noise tests on the encrypted image produced by a security system based on a joint transform correlator and the Fresnel transform

In this work, the occlusion and noise test on the encrypted image produced by a joint transform correlator-based encryption system in the Fresnel domain (FrD) are computed and presented, in order to check the performance of this security system with respect to the image quality resulting in the decryption process for the retrieved image. The encryption system based on a joint transform correlator (JTC) in the FrD was proposed by us, with the purpose of using a lensless optical setup. We test the performance of this security system when the encrypted image is affected by common sources of degradation such as noise (additive and multiplicative) or partial occlusion. Finally, we evaluate the performance and robustness of the security system in the FrD by using the metric of the root mean square error (RMSE) between the image to encrypt and the decrypted image when the encrypted image is degraded by noise or modified by occlusion.This research has been funded by the Universidad de La Guajira, Colombia, and the Spanish Ministerio de Ciencia e Innovación and Fondos FEDER (Project DPI2013-43220-R).Peer ReviewedPostprint (published version

Nonlinear joint transform correlator architectures for images encryption, decryption and authentication systems

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Static and dynamic amplitude modulation of light in a twisted nematic liquid crystal display

A SLM has been experimentally characterized in terms of amplitude modulation versus the gray level distribution (input signal) electronically addressed to the pixelated display in two conditions: input constant with time, and time variant input with increasing frame rate. The SLM considered in this work was a twisted nematic liquid crystal display manufactured by CRL (XGA2 model) that operates on the transmitted light. The influence of some technical speci cations such as gamma correction, brightness and contrast of this SLM have been considered as well.Postprint (published version

Theory for three dimensional dynamic simulation of towed cable-body systems

SIGLEAvailable from British Library Document Supply Centre- DSC:DX76165 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Influence of a perturbation in the Gyrator domain for a joint transform correlator-based encryption system

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