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17 pages, 19160 KB

Open AccessArticle

A Complementary Approach for Securing and Anti-Counterfeiting of Valuable Documents Based on Encryption of Computer-Generated Hologram

by Zakaria E. Ahmed, Rania M. Abdelazeem, Yasser A. Attia, Tawfik A. Khattab, Claas Falldorf, Ralf B. Bergmann and Mostafa Agour

Sensors 2025, 25(8), 2410; https://doi.org/10.3390/s25082410 - 10 Apr 2025

Cited by 4 | Viewed by 2034

Abstract

We present a novel approach for securing valuable documents using a complementary approach based on the encryption of computer-generated holograms (CGHs). The proposed approach utilizes the well-known iterative Fourier transform algorithm (IFTA) to generate a phase-only CGH for valuable digital and/or physical documents. [...] Read more.

We present a novel approach for securing valuable documents using a complementary approach based on the encryption of computer-generated holograms (CGHs). The proposed approach utilizes the well-known iterative Fourier transform algorithm (IFTA) to generate a phase-only CGH for valuable digital and/or physical documents. The generated CGH is then secured by binary phase randomization, which is implemented using the symmetric encryption technique, exclusive OR (XOR). The reconstruction process for the calculated secured CGHs varied slightly depending on whether the documents were digital or physical. For digital documents, reconstruction was performed using a symmetric decryption key followed by an inverse Fourier transform (IFFT). On the other hand, the reconstruction of the physical document involved two additional processes: printing and scanning. To evaluate the quality of the digital reconstruction, the speckle signal-to-noise ratio (SSNR) was estimated for both printed grayscale and binary CGHs. The security analysis of the XOR-encrypted CGH was quantitatively evaluated to ensure the level of protection against various cryptographic attacks such as plaintext and brute-force attacks. The results revealed that the combination of phase CGHs and the XOR encryption/decryption provides robust cryptographic protection for valuable documents, benefiting document security and anti-counterfeiting. Full article

(This article belongs to the Section Sensing and Imaging)

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16 pages, 15800 KB

Open AccessArticle

Advancement of the DRPE Encryption Algorithm for Phase CGHs by Random Pixel Shuffling

by Alfonso Blesa and Francisco J. Serón

Appl. Sci. 2025, 15(8), 4120; https://doi.org/10.3390/app15084120 - 9 Apr 2025

Cited by 1 | Viewed by 946

Abstract

This work presents an optical encryption process for various types of information related to 3D worlds (scenes) or 2D images, utilizing Computer-Generated Holograms (CGHs). It also introduces a modification to the Dual Random Phase Encoding (DRPE) encryption algorithm by incorporating pixel shuffling. This [...] Read more.

This work presents an optical encryption process for various types of information related to 3D worlds (scenes) or 2D images, utilizing Computer-Generated Holograms (CGHs). It also introduces a modification to the Dual Random Phase Encoding (DRPE) encryption algorithm by incorporating pixel shuffling. This proposal enables the use of either a single key for both pixel shuffling and phase mask definition or two independent keys. The latter option is particularly advantageous in applications that require the involvement of two independent agents to retrieve the original plaintext. The dimension of the CGHs determines the size of the keys based on the random generation of values by cryptographically secure algorithms, so the use of arithmetic encryption is proposed for data compression. However, this proposal allows the use of other algorithms described in the literature to generate the shuffle and phase matrices. The complete workflow is described starting from the synthesis of a 3D scene, defined by a mesh of triangles with shape and appearance modeling, or 2D images of any level of geometric or visual complexity using computer graphics; its storage in a CGH, the encryption and decryption process, and finally, the results obtained in the laboratory and by simulation are shown. The similarity between different encryption levels is measured by the Pearson Coefficient to evaluate the results obtained. Full article

(This article belongs to the Special Issue Digital Holography: Advancements, Applications, and Challenges)

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13 pages, 6315 KB

Open AccessArticle

Watermarking and Encryption for Holographic Communication

by Zehao He, Kexuan Liu and Liangcai Cao

Photonics 2022, 9(10), 675; https://doi.org/10.3390/photonics9100675 - 21 Sep 2022

Cited by 7 | Viewed by 3024

Abstract

Holographic communication is a three-dimensional (3D) video communication technology based on computer-generated holograms (CGHs) which has the potential to give users a more realistic visual perception. As this is an emerging field, the encrypted encoding and decoding methods in holographic communication have not [...] Read more.

Holographic communication is a three-dimensional (3D) video communication technology based on computer-generated holograms (CGHs) which has the potential to give users a more realistic visual perception. As this is an emerging field, the encrypted encoding and decoding methods in holographic communication have not been widely studied. In this work, a watermarking and encryption method for holographic communication is proposed. A watermark is inserted into the original image using the discrete cosine transform before the calculation of the CGH, while a secret key is employed to produce the encrypted CGH during the holographic calculation. Through the proposed watermarking and encryption method, the signal of holographic communication is difficult to decrypt. Even if the signal is decrypted, the source of the leak is easy to trace due to the existence of the watermark. The watermarking and encryption method can provide a practical solution for the privacy protection and copyright protection of 3D video communication. Full article

(This article belongs to the Special Issue Advances and Application of Imaging on Digital Holography)

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11 pages, 7175 KB

Open AccessCommunication

Holographic Encryption Applications Using Composite Orbital Angular Momentum Beams

by Nian Zhang, Baoxing Xiong, Xiang Zhang and Xiao Yuan

Photonics 2022, 9(9), 605; https://doi.org/10.3390/photonics9090605 - 26 Aug 2022

Cited by 10 | Viewed by 3555

Abstract

Optical orbital angular momentum (OAM) holography has been developed and implemented as a vital method for optical encryption. However, OAM holography can only be encoded and decoded with an OAM beam, which limits the level of optical encryption. Here, composite OAM beams are [...] Read more.

Optical orbital angular momentum (OAM) holography has been developed and implemented as a vital method for optical encryption. However, OAM holography can only be encoded and decoded with an OAM beam, which limits the level of optical encryption. Here, composite OAM beams are introduced using a computer-generated hologram (CGH) for holographic encryption. The target image is encoded with composite helical mode indices, and the OAM holographic image can only be reconstructed under a specific illuminating composite OAM beam. The experimental results are consistent with the theoretical design and numerical simulations, verifying that composite OAM beams can provide a higher security level for optical holographic encryption. The proposed method can be used to enhance anti-counterfeiting applications, secure communication systems, and imaging systems. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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12 pages, 3633 KB

Open AccessArticle

Reducing Defocused-Information Crosstalk to Multi-View Holography by Using Multichannel Encryption of Random Phase Distribution

by Chih-Hao Chuang, Chien-Yu Chen, Hsuan-Ting Chang, Hoang-Yan Lin and Chuan-Feng Kuo

Appl. Sci. 2022, 12(3), 1413; https://doi.org/10.3390/app12031413 - 28 Jan 2022

Cited by 5 | Viewed by 3014

Abstract

A new optical encryption algorithm, called the random-phase encryption algorithm, is proposed in this study. When this algorithm was applied in constructing computer-generated holograms, the out-of-focus image crosstalk was effectively reduced, and the image quality was greatly enhanced. In this study, the researchers [...] Read more.

A new optical encryption algorithm, called the random-phase encryption algorithm, is proposed in this study. When this algorithm was applied in constructing computer-generated holograms, the out-of-focus image crosstalk was effectively reduced, and the image quality was greatly enhanced. In this study, the researchers encrypted each multi-depth or multi-view random phase sub-image with the phase-locked key to generate multi-channel encryption phase information. During the reconstruction, the switch of the phase-locked key of the sub-image was found to achieve different image reconstruction effects with different views or depths. This algorithm proved to substantially reduce the out-of-focus image crosstalk and to enhance the reconstruction quality of the original computer holography without concerning the mutual interference among the information of each view for multi-view and multi-depth holograms. Full article

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21 pages, 10792 KB

Open AccessArticle

Adaptive Digital Hologram Binarization Method Based on Local Thresholding, Block Division and Error Diffusion

by Pavel A. Cheremkhin, Ekaterina A. Kurbatova, Nikolay N. Evtikhiev, Vitaly V. Krasnov, Vladislav G. Rodin and Rostislav S. Starikov

J. Imaging 2022, 8(2), 15; https://doi.org/10.3390/jimaging8020015 - 18 Jan 2022

Cited by 20 | Viewed by 5062

Abstract

High-speed optical reconstruction of 3D-scenes can be achieved using digital holography with binary digital micromirror devices (DMD) or a ferroelectric spatial light modulator (fSLM). There are many algorithms for binarizing digital holograms. The most common are methods based on global and local thresholding [...] Read more.

High-speed optical reconstruction of 3D-scenes can be achieved using digital holography with binary digital micromirror devices (DMD) or a ferroelectric spatial light modulator (fSLM). There are many algorithms for binarizing digital holograms. The most common are methods based on global and local thresholding and error diffusion techniques. In addition, hologram binarization is used in optical encryption, data compression, beam shaping, 3D-displays, nanofabrication, materials characterization, etc. This paper proposes an adaptive binarization method based on a combination of local threshold processing, hologram division into blocks, and error diffusion procedure (the LDE method). The method is applied for binarization of optically recorded and computer-generated digital holograms of flat objects and three-dimensional scenes. The quality of reconstructed images was compared with different methods of error diffusion and thresholding. Image reconstruction quality was up to 22% higher by various metrics than that one for standard binarization methods. The optical hologram reconstruction using DMD confirms the results of the numerical simulations. Full article

(This article belongs to the Special Issue New and Specialized Methods of Image Compression)

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15 pages, 9509 KB

Open AccessArticle

Optical Encryption Based on Computer Generated Holograms in Photopolymer

by Taihui Wu, Jianshe Ma, Chengchen Wang, Haibei Wang, Liangcai Cao and Ping Su

Polymers 2021, 13(9), 1358; https://doi.org/10.3390/polym13091358 - 21 Apr 2021

Cited by 7 | Viewed by 3418

Abstract

An optical encryption method based on computer generated holograms printing of photopolymer is presented. Fraunhofer diffraction is performed based on the Gerchberg-Saxton algorithm, and a hologram of the Advanced Encryption Standard encrypted Quick Response code is generated to record the ciphertext. The holograms [...] Read more.

An optical encryption method based on computer generated holograms printing of photopolymer is presented. Fraunhofer diffraction is performed based on the Gerchberg-Saxton algorithm, and a hologram of the Advanced Encryption Standard encrypted Quick Response code is generated to record the ciphertext. The holograms of the key and the three-dimensional image are generated by the angular spectrum diffraction algorithm. The experimental results show that large-size encrypted Quick Response (QR) code and miniature keys can be printed in photopolymers, which has good application prospects in optical encryption. This method has the advantages of high-density storage, high speed, large fault tolerance, and anti-peeping. Full article

(This article belongs to the Section Polymer Applications)

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Graphical abstract

12 pages, 8253 KB

Open AccessArticle

A Content Hiding Method for Digital Hologram Using Multiple Fresnel Diffraction

by Young-Ho Seo, Yoon-Hyuk Lee and Dong-Wook Kim

Appl. Sci. 2020, 10(14), 4897; https://doi.org/10.3390/app10144897 - 16 Jul 2020

Cited by 2 | Viewed by 2679

Abstract

A digital hologram (DH) is so highly valued that it needs to be protected from exposure to an unpermitted person, which could be done by a content encryption. We propose an encryption scheme for digital holograms, whose goal is to hide their information [...] Read more.

A digital hologram (DH) is so highly valued that it needs to be protected from exposure to an unpermitted person, which could be done by a content encryption. We propose an encryption scheme for digital holograms, whose goal is to hide their information with maximal visual distortion and minimal ration of the encrypted data. It uses the characteristics of the Fresnel transform and signal processing techniques. As the diffraction distance increases the region containing the object information relative to the whole diffraction plane becomes smaller. Therefore our scheme diffracts a given digital hologram twice: the first transform for reconstructing the image contained by the hologram and the second transform for concentrating the energy of the object into a small region. Then only the energy-concentrated region is encrypted to reduce the amount of data to be encrypted. Experimental results show that when the diffraction distance of the second transform is about 20 m, the encryption ratio is only 0.0058% of the hologram data, which is enough to hide the object information unrecognizably. Full article

(This article belongs to the Section Optics and Lasers)

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17 pages, 4236 KB

Open AccessArticle

Angle Multiplexing Optical Image Encryption in the Fresnel Transform Domain Using Phase-Only Computer-Generated Hologram

by Hsuan T. Chang, Yao-Ting Wang and Chien-Yu Chen

Photonics 2020, 7(1), 1; https://doi.org/10.3390/photonics7010001 - 18 Dec 2019

Cited by 20 | Viewed by 4689

Abstract

We propose an angle multiplexing method for optics-based image encryption using a phase-only computer-generated hologram (POCGH) in the tilted Fresnel transform (TFrT) domain. Modified Gerchberg-Saxton algorithms, based on the three types of rotation manipulation in both the hologram and reconstruction planes, are used [...] Read more.

We propose an angle multiplexing method for optics-based image encryption using a phase-only computer-generated hologram (POCGH) in the tilted Fresnel transform (TFrT) domain. Modified Gerchberg-Saxton algorithms, based on the three types of rotation manipulation in both the hologram and reconstruction planes, are used with their corresponding TFrT parameters to extract the phase-only functions (POFs) of the target images. All the extracted POFs are then phase-modulated and summed to obtain the final POCGH, which is capable of multiplexing and avoiding overlap in the reconstructed images. The computer simulation results show that the images corresponding to the various rotation manipulations at the hologram and image reconstruction planes can be successfully restored with high correlation coefficients. Due to the encrypted nature of the multiplexed images, a higher system security level can be achieved, as the images can only be correctly displayed when all the required parameters in the TFrT are available. The angle sensitivity on the image quality for each manipulation is also investigated. Full article

(This article belongs to the Section Optical Communication and Network)

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14 pages, 8212 KB

Open AccessArticle

An Adaptive and Secure Holographic Image Watermarking Scheme

by Chuying Yu, Xiaowei Li, Xinan Chen and Jianzhong Li

Entropy 2019, 21(5), 460; https://doi.org/10.3390/e21050460 - 2 May 2019

Cited by 14 | Viewed by 3962

Abstract

A novel adaptive secure holographic image watermarking method in the sharp frequency localized contourlet transform (SFLCT) domain is presented. Based upon the sine logistic modulation map and the logistic map, we develop an encrypted binary computer-generated hologram technique to fabricate a hologram of [...] Read more.

A novel adaptive secure holographic image watermarking method in the sharp frequency localized contourlet transform (SFLCT) domain is presented. Based upon the sine logistic modulation map and the logistic map, we develop an encrypted binary computer-generated hologram technique to fabricate a hologram of a watermark first. Owing to the enormous key space of the encrypted hologram, the security of the image watermarking system is increased. Then the hologram watermark is embedded into the SFLCT coefficients with Schur decomposition. To obtain better imperceptibility and robustness, the entropy and the edge entropy are utilized to select the suitable watermark embedding positions adaptively. Compared with other watermarking schemes, the suggested method provides a better performance with respect to both imperceptibility and robustness. Experiments show that our watermarking scheme for images is not only is secure and invisible, but also has a stronger robustness against different kinds of attack. Full article

(This article belongs to the Special Issue Entropy Based Data Hiding)

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