Optical Encryption Method Research Articles

Design and Simulation of Physical Layer Security for Next Generation Intelligent Optical Networks

With the latest technological advancements and attractive features of next generation intelligent optical networks such as high bandwidth, low power consumption, and low transmission loss, etc., they have been considered as most viable solution to satisfy promptly growing bandwidth demands. However, main optical network components bring forth a set of security challenges and reliability issues, accompanied by new vulnerabilities within the network. This paper proposes a new design for an optical encryption and decryption method for enhancing optical network security using p–i–n photodiode which generates Pseudo Random Binary Sequence (PRBS) as a shot noise fluctuations and wavelength converter based design using Semiconductor Optical Amplifier based XOR gate which utilizes Cross-Phase Modulation. The system performance based on Bit Error Rate and Q factor are analyzed at different data rates for different link lengths up to 100 km using OptiSystem. It is observed that error free transmission with a BER of 10–12 is achieved a data rate of 10 Gbps for a link length of only 30 km for the system with PIN photodiode’s shot noise being used for PRBS sequence generation. However, wavelength conversion based system enables transmission of signal at 10Gbps signal up to a link length of 90 km.

Optical encryption based on biometrics and single-pixel imaging with random orthogonal modulation

Computational ghost imaging (CGI), as a novel single-pixel imaging (SPI) technique, has a great potential and bright prospect in the field of optical information security owing to its encryption performances of data compression and real-value ciphertext. However, there are some vulnerabilities in CGI-based encryption technique, such as serious noise in the decrypted result, huge amount of keys, and several potential security loopholes. To address these issues, we propose an optical encryption method based on biometrics and SPI with random orthogonal modulation (ROM) in this paper. The ROM, which is generated by Hadamard matrix, not only improves the clarity of the decrypted images but also reduces the amount of keys to be transmitted. Besides, the security loophole for forgery attack in CGI-based encryption system is effectively blocked by fingerprint key. Both numerical simulations and optical experiments are carried out to test the feasibility and performance of our proposed method.

Time scrambling and decoy-state quantum key distribution for optical physical layer encryption

We propose an optical physical layer encryption method based on real-time optical signal temporal scrambling and decoy-state quantum key distribution. The real-time optical signal processing is operating with an array of tunable Fabry-Perot cavities by using the updating and synchronization keys. Based on this scheme, an experimental demonstration is given to realize secure communication for optical physical layer in a standard 10 Gbps data transmission with quantum key distribution in real time. An on-line transmitted data over 100 km of a standard single mode fiber is realized with power penalty of as low as 3.45 dB, where the average key generation rate is better than 800 bps. The experimental results indicate that, the proposed encryption scheme of dynamic scrambling with quantum keys exhibits significantly potential for improving the confidentiality of optical physical layer.

An Optical Image Encryption Method Using Hopfield Neural Network.

In this paper, aiming to solve the problem of vital information security as well as neural network application in optical encryption system, we propose an optical image encryption method by using the Hopfield neural network. The algorithm uses a fuzzy single neuronal dynamic system and a chaotic Hopfield neural network for chaotic sequence generation and then obtains chaotic random phase masks. Initially, the original images are decomposed into sub-signals through wavelet packet transform, and the sub-signals are divided into two layers by adaptive classification after scrambling. The double random-phase encoding in 4f system and Fresnel domain is implemented on two layers, respectively. The sub-signals are performed with different conversions according to their standard deviation to assure that the local information’s security is guaranteed. Meanwhile, the parameters such as wavelength and diffraction distance are considered as additional keys, which can enhance the overall security. Then, inverse wavelet packet transform is applied to reconstruct the image, and a second scrambling is implemented. In order to handle and manage the parameters used in the scheme, the public key cryptosystem is applied. Finally, experiments and security analysis are presented to demonstrate the feasibility and robustness of the proposed scheme.

An Optical Image Encryption Algorithm Based on a Fractional-Order Laser Hyperchaotic System

In recent years, image encryption schemes based on optical methods have been extensively studied. However, possible optical encryption methods in combination with fractional-order laser hyperchaotic systems have not been reported. Therefore, an optical image encryption scheme based on fractional Fourier transform and five-dimensional host-induced nonlinearity fractional-order laser hyperchaotic system is studied in this paper. Firstly, the dynamical characteristics of the proposed fractional-order laser hyperchaotic system are analyzed, and the DSP platform is used to realize the system. Then, a novel image encryption scheme is proposed combining BP neural network, GF(17) domain diffusion and hyperchaotic, random point scrambling algorithm. Finally, the performance of the encryption scheme is analyzed in detail. This work provides an experimental basis and theoretical guidance for image secure communication combining fractional-order laser hyperchaotic systems and optical methods and offers a new research perspective for optical image encryption.

Optical information encryption based on partially-update iterative system with azimuth multiplexing

This paper introduces an optical information encryption method based on partially-update iteration system with azimuth multiplexing. Multiple high-definition pictures are stored in multiple QR codes as amplitude constraints, and then encrypted in Fresnel domain by azimuth multiplexing. Due to the proposal of the enhancement system with partial update of the phase mask, the number of pictures can be encrypted increases. The security of the system is guaranteed by azimuth multiplexing, and the multiplexing capacity is jointly guaranteed by phase partial update system and QR code. The decoded QR code can extract the encrypted information without much quality loss. Simulation results show that the scheme has a large-capacity information storage, high security, robustness and practicability.

Multi-image optical encryption method of JTC system combining CGH and frequency shift

Multi-image optical encryption method of JTC system combining CGH and frequency shift

Optical color image cryptosystem based on interference principle and deep learning

In this work, we propose a method for optical color image encryption based on interference principle and deep learning technique. After the interferograms being collected through three channels, a color image to be encoded can be captured optically and transformed into a color interferogram. An end-to-end DL model is trained to derive the mapping relationship between the interferograms and their original plaintexts. In this method, Arnold transform is used to scramble the recorded interferogram for achieving high security. The primary color image can be decrypted by using inverse Arnold transform and the trained learning model. The method provides the ability to decrypt a color image from only one color interferogram, which couldn’t be achieved by using conventional methods. In the decryption process, the optical keys used for traditional decryption are not required. The effectiveness and security of the cryptosystem are verified by computer simulations.

Direction Controllable Nano‐Patterning of Titanium by Ultrafast Laser for Surface Coloring and Optical Encryption

AbstractMetasurfaces constructed from subwavelength nanostructures provide a route for surface coloring and optical encryption. Because of the high transmittance and refractive index, titanium dioxide (TiO2) is a candidate for visible metasurfaces, and its nano‐processing is essential for TiO2 metasurfaces. Herein, a direction‐controllable ultrafast laser nano‐patterning approach is reported for writing TiO2 nanostructures on titanium. The writing direction is controlled by adjusting the polarization of incident laser. Due to the localization of pulse energy inside the formed nanostructures, diverse planar patterns with feature sizes smaller than the diffraction limit are written. A strip‐shaped nanostructure with the width of 344 nm, parallel nanostructures with the center‐to‐center distance down to 370 nm, and a “THU” pattern with the height of 790 nm are achieved. Grating TiO2 nanostructures with various periods are fabricated for surface coloring and printing. Based on the anisotropic optical behaviors of grating‐type nanostructures, encrypting information by orthogonal scans is demonstrated as an optical encryption strategy. This nano‐patterning approach opens a route for the fabrication of TiO2 metasurfaces, and provides a new method for surface coloring and optical encryption.

Holographic and speckle encryption using deep learning.

Vulnerability analysis of optical encryption schemes using deep learning (DL) has recently become of interest to many researchers. However, very few works have paid attention to the design of optical encryption systems using DL. Here we report on the combination of the holographic method and DL technique for optical encryption, wherein a secret image is encrypted into a synthetic phase computer-generated hologram (CGH) by using a hybrid non-iterative procedure. In order to increase the level of security, the use of the steganographic technique is considered in our proposed method. A cover image can be directly diffracted by the synthetic CGH and be observed visually. The speckle pattern diffracted by the CGH, which is decrypted from the synthetic CGH, is the only input to a pre-trained network model. We experimentally build and test the encryption system. A dense convolutional neural network (DenseNet) was trained to estimate the relationship between the secret images and noise-like diffraction patterns that were recorded optically. The results demonstrate that the network can quickly output the primary secret images with high visual quality as expected, which is impossible to achieve with traditional decryption algorithms.

Optical multiple-image authentication and encryption based on phase retrieval and interference with sparsity constraints

An optical multiple-image authentication and encryption method based on phase retrieval algorithm (PRA) in the Fresnel domain and interference with sparsity constraints is proposed. In our proposed method, sparse phase and space multiplexing technique are respectively introduced to authentication and encryption for multiple-image. Each target image is respectively encrypted into two phase-only masks, which contain the phase data generated from three binary images by applying PRA in the Fresnel domain and need to be verified before used for decryption. That the target images are respectively reconstructed by using different decryption keys in the proposed method increases the security of the cryptosystem. Numerical simulation shows that the proposed method has high multiplexing capacity and security.

Optical Encryption Based on Computer Generated Holograms in Photopolymer.

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.

Secure Optical Encryption Technique for Real Time Security Related Applications - A Review

Recent development in the digital system shows that data security is most important and that optical encryption can be used not only to keep signals confidential but also to authenticate information. By integrating sparsity constraint with optical encryption, the reconstructed decoder image is not always visually recognizable, but can be authenticated using optical correlation means methods. Traditional optical encryption methods can add an extra layer of security to this design as it authenticates without leaking primary signal information. This paper discusses advances in optical authentication and includes theoretical principles and implementation examples to demonstrate the workings of typical authentication systems. Benchmarking and upcoming possibilities are discussed and it is hoped that this review work useful in advancing the field of optical safety.

Liquid crystal integrated metadevice for reconfigurable hologram displays and optical encryption.

The ultimate goal of metasurface research in recent years is to apply metasurface to reality applications and improve the performance compared to its counterpart, namely conventional optical elements with the same function. Inspired by the application of electrically addressing spatial light modulator (EA-SLM) and based on the binary holographic algorithm, here we propose a reconfigurable metadevice integrated with the nematic liquid crystal (NLC). The smart metadevice directly uses the subwavelength antennas as the main contributor to the phase accumulation instead of the NLC layer. By applying different electrical modulation patterns on the NLC, the metadevice can realize the function of dynamic holographic display as traditional SLMs but features in smaller size, higher resolution and lager field of view. In addition, we improved the existing computer-generated hologram algorithm to generate three holograms with quantitative correlation and also propose a new optical encryption method based on our metadevice. The encryption method needs four elements in total to decrypt and can fully meets the requirements of the various encrypted content. We believe such metadevice paves the way for the new generation of micro-optical display and optical encryption devices.

Low-noise and fast three-dimensional information encryption based on the double-phase method

A low-noise and fast optical encryption method for three-dimensional (3-D) information using the double-phase method is proposed. First, the 3-D information is encoded into a phase-only hologram (POH) by the angular-spectrum diffraction and the double-phase method. Second, the chaotic random phase mask (CRPM) is generated by the hybrid logical map and the iterative chaotic map with infinite collapses map to modulate the POH and obtain the ciphertext. As the secret key, the CRPM cannot only improve the secret key space of the scheme but also achieve the purpose of scrambling and hiding 3-D information. Third, the background noise of the decrypted image is successfully reduced by the cross-shaped filter, which is designed for the first time based on the POH spectrum distribution. The proposed scheme has successfully improved the encryption speed of the 3-D information and the quality of the reconstructed images. Numerical simulation and optical results show the effectiveness and feasibility of the proposed encryption scheme.

Optical encryption using uncorrelated characteristics of dynamic scattering media and spatially random sampling of a plaintext.

Scattering media are generally regarded as an obstacle in optical imaging. However, the scattering of a diffuser can be exactly taken as an advantage to act as random phase masks in the field of optical encryption to enhance information security. Here, we propose and demonstrate a dynamic diffuser based optical encryption method, which increases the ciphering strength by exploiting the uncorrelated characteristics of the dynamic diffuser as well as randomly sampling the plaintext multiple times. The light emitted from a randomly sampled plaintext passing through the dynamic diffuser generates noise-like speckles, and then SNR of the recorded speckles is further reduced for obtaining the ciphertexts, which makes COA using PRA almost impossible. The specific uncorrelated characteristics of the dynamic diffuser make the ciphertexts and the PSF keys of the optical encryption unique. Therefore, only authorized users who mastered the keys can decrypt the plaintext. The proposed method is very simple and flexible since it can also achieve the encryption offline by performing convolutions on partial-plaintexts with pre-recorded uncorrelated PSFs to generate speckle patterns and then reducing their SNR to obtain the ciphertexts. This type of encryption technique has a promising prospect in applications involving images and/or videos information encryption owing to its simplicity and flexibility.

The optical image compression and encryption method based on Fresnel diffraction and discrete wavelet transform

Generally, the length of ciphertexts and encryption keys are usually longer than that of the plaintexts. In this study, an optical image compression method based on Fresnel diffraction and discrete wavelet transform is proposed. The Fresnel diffraction is used for acquiring more low-frequency information. The proposed method is a plaintext pre-processing scheme and can be adopted in any cryptosystem where the encryption key cannot be shortened effectively. In this method, we can obtain a compressed image whose length is shorter them the plaintext. By encrypting the compressed image obtained, the length of ciphertext and encryption keys can be reduced. In addition, some compression parameters naturally existed in the proposed Fresnel diffraction optical setup are also needed for decompression. Moreover, the proposed method can also further compress the plaintext if a slight increment of information loss is allowed. Besides, the realization of this scheme is simple, hence no substantial cost is added for a given optical cryptosystem. Besides the statistical analysis, extensive numerical simulations have been carried out to validate the feasibility, robustness, sensibility of the proposed method.

Optical multimodal biometric encryption that uses digital holography

In this paper, we propose an optical multimodal biometric encryption technique which uses digital holography (DH) for multiple biometric recording and successive optical encryption methods, by means of keys generated from biometric data. Physiological biometrics, such as fingerprints or iris scans, along with behavioral biometrics such as voice, are recorded simultaneously as multimodal biometrics, using multi-parameter off-axis DH. Moreover, multiple biometrics embedded in the same holograms are encrypted using the Fresnel domain double random phase encoding method, in which keys are generated from biometric data via a phase retrieval algorithm. By employing the decryption procedure for this encoding method, along with the correct keys and reconstruction parameters of DH, the original multimodal biometrics can be successfully retrieved . The proposed method provides multimodal biometrics with a higher level of security by availing itself of the advantages of optical techniques. Our proposed multimodal biometric security scheme is demonstrated and validated by the results of the optical recording and encryption of biometric data presented below.

Optical multiple images encryption system based on ellipsometry reconstruction

In this paper, an optical multiple image encryption method based on ellipsometry reconstruction is proposed. In our proposal, the cryptosystem is designed as multiple paths, and each path is used to encrypt one image. In each path, one original image is decomposed into two phase only masks (POMs) using the interference method. Then, every two masks decomposed from the same original image are encoded onto the spatial light modulator (SLM) to generate an elliptically polarized light (EPL) with specific amplitude and polarization. After that, each light passes through a linear polarizer. CCD is used to record the sum of the intensity of these path outputs, which is ciphertext. Jones matrix is used to describe these procedures. Moreover, our proposed encryption system has certain anti-attack ability. Computer simulations are conducted to verify the correctness and validity of our proposed method.

Optical color image encryption based on Hadamard single-pixel imaging and Arnold transformation

An optical color image encryption method based on Hadamard single-pixel imaging (SPI) and Arnold transformation is proposed, in which, optical full-color image encryption with good imaging quality and high security performance can be accomplished by only one bucket detector (BD). In the encryption process, after controlling and modulating the Hadamard matrix by the coefficient matrix key, three different sets of colored Hadamard patterns are generated to be projected onto the target colored object; Subsequently, the collected experimental data: R, G, and B components are detected by a BD, which are then scrambled by Arnold transformation to further increase the security; Finally the colored ciphertext image can be recombined and obtained to transferring to the receivers. During the decryption, with the colored ciphertext and all the corrected keys, the original secret color image can be successfully decrypted by the extraction of R, G, B components, inverse Arnold transformation, the correlated computation in SPI, and inverse Hadamard transformation. The feasibility of this method and its robustness against some types of attacks are verified by both computer simulations and optical experiments.