Optical encryption scheme based on spread spectrum ghost imaging

An optical encryption(OE) scheme based on the spread spectrum ghost imaging(SSGI), named as SSGI-OE, is proposed to obtain a high security with a smaller key. In the scheme, the randomly selected row number of a Hadamard matrix of order N is used as the secure key, and shared with the authorized user, Bob, through a private channel. Each corresponding row vector of the order-N Hadamard matrix is then used as the direct sequence code to modulate a speckle pattern for the ghost imaging system, and an image is encrypted with the help of the SSGI. The measurement results from the bucket detector, named as ciphertext, are then transmitted to Bob through a public channel. The illuminating speckle patterns are also shared with Bob by the public channel. With the correct secure key, Bob could reconstruct the image with the aid of the SSGI system, whereas the unauthorized user, Eve, could not obtain any useful information of the encrypted image. The numerical simulations and experimental results show that the proposed scheme is feasible with a higher security and a smaller key. For the 32 × 32 pixels image, the number of bits sent from Alice to Bob by using SSGIOE(M = 1024, N = 2048) scheme is only 0.0107 times over a computational ghost imaging optical encryption scheme.When the eavesdropping ratio(ER) is less than 40%, the eavesdropper cannot acquire any information of the encrypted image. The extreme circumstance for the proposed SSGI-OE scheme is also discussed, where the eavesdropper begins to extract the information when ER is up to 15%.

Cascaded liquid crystal holography for optical encryption

Cascaded holography coupled with the secret-sharing scheme has recently gained considerable attention due to its enhanced information processing and encryption capabilities.Here,we propose a new holographic iterative algorithm and present the implementation of cascaded liquid crystal(LC)holography for optical encryption.Each LC layer acts as the secret key and can generate a distinct holographic image.By cascading two LC elements,a new holographic image is formed.Additionally,we showcase the dynamic optical encryption achieved by electrically switching LCs with combined electric keys.This work may offer promising applications in optical cryptography,all-optical computing,and data storage.

Metal−Organic Framework-Based Ultrafast Logic Gates for High-Security Optical Encryption

Optical logic gates call for materials with giant optical nonlinearity to break the current performance bottleneck.Metal–organic frameworks(MOFs)provide an intriguing route to achieve superior optical nonlinearity benefitting from structural diversity and design flexibility.However,the potential of MOFs for optoelectronics has been largely overlooked and their applications in optical logic have not been exploited.Here,through temporally manipulating the nonlinear optical absorption process in porphyrin-based MOFs,we have successfully developed AND and XOR logic gates with an ultrafast speed approaching 1 THz and an on–off ratio above 90%.On this basis,all-optical information encryption is further demonstrated using transmittance as primary codes,which shows vast prospects in avoiding the disclosure of security information.To the best of our knowledge,this is the first exploration of MOFs for applications in ultrafast optical logic devices and information encryption.

Optical image encryption algorithm based on a new four-dimensional memristive hyperchaotic system and compressed sensing

Some existing image encryption schemes use simple low-dimensional chaotic systems, which makes the algorithms insecure and vulnerable to brute force attacks and cracking. Some algorithms have issues such as weak correlation with plaintext images, poor image reconstruction quality, and low efficiency in transmission and storage. To solve these issues,this paper proposes an optical image encryption algorithm based on a new four-dimensional memristive hyperchaotic system(4D MHS) and compressed sensing(CS). Firstly, this paper proposes a new 4D MHS, which has larger key space, richer dynamic behavior, and more complex hyperchaotic characteristics. The introduction of CS can reduce the image size and the transmission burden of hardware devices. The introduction of double random phase encoding(DRPE) enables this algorithm has the ability of parallel data processing and multi-dimensional coding space, and the hyperchaotic characteristics of 4D MHS make up for the nonlinear deficiency of DRPE. Secondly, a construction method of the deterministic chaotic measurement matrix(DCMM) is proposed. Using DCMM can not only save a lot of transmission bandwidth and storage space, but also ensure good quality of reconstructed images. Thirdly, the confusion method and diffusion method proposed are related to plaintext images, which require both four hyperchaotic sequences of 4D MHS and row and column keys based on plaintext images. The generation process of hyperchaotic sequences is closely related to the hash value of plaintext images. Therefore, this algorithm has high sensitivity to plaintext images. The experimental testing and comparative analysis results show that proposed algorithm has good security and effectiveness.

Deep-learning-based ciphertext-only attack on optical double random phase encryption

Optical cryptanalysis is essential to the further investigation of more secure optical cryptosystems.Learning-based at-tack of optical encryption eliminates the need for the retrieval of random phase keys of optical encryption systems but it is limited for practical applications since it requires a large set of plaintext-ciphertext pairs for the cryptosystem to be at-tacked.Here,we propose a two-step deep learning strategy for ciphertext-only attack(COA)on the classical double ran-dom phase encryption(DRPE).Specifically,we construct a virtual DRPE system to gather the training data.Besides,we divide the inverse problem in COA into two more specific inverse problems and employ two deep neural networks(DNNs)to respectively learn the removal of speckle noise in the autocorrelation domain and the de-correlation operation to retrieve the plaintext image.With these two trained DNNs at hand,we show that the plaintext can be predicted in real-time from an unknown ciphertext alone.The proposed learning-based COA method dispenses with not only the retrieval of random phase keys but also the invasive data acquisition of plaintext-ciphertext pairs in the DPRE system.Numerical simulations and optical experiments demonstrate the feasibility and effectiveness of the proposed learning-based COA method.

Measurement of optical coherence structures of random optical fields using generalized Arago spot experiment

The optical coherence structures of random optical fields can determine beam propagation behavior,light–matter interactions,etc.Their performance makes a light beam robust against turbulence,scattering,and distortion.Recently,we proposed optical coherence encryption and robust far-field optical imaging techniques.All related applications place a high demand on precision in the experimental measurements of complex optical coherence structures,including their real and imaginary parts.Past studies on these measurements have mainly adopted theoretical mathematical approximations,limited to Gaussian statistic involving speckle statistic(time-consuming),or used complicated and delicate optical systems in the laboratory.In this study,we provide:a robust,convenient,and fast protocol to measure the optical coherence structures of random optical fields via generalized Arago(or Poisson)spot experiments with rigorous mathematical solutions.Our proposal only requires to capture the intensity thrice,and is applicable to any optical coherence structures,regardless of their type or optical statistics.The theoretical and experimental results demonstrated that the real and imaginary parts of the structures could be simultaneously recovered with high precision.We believe that such a protocol can be widely employed in phase measurement,optical imaging,and image transfer.

Attack on Optical Double Random Phase Encryption Based on the Principle of Ptychographical Imaging

The principle of ptychography is applied in known plain text attack on the double random phase encoding （DRPE） system. We find that with several pairs of plain texts and cipher texts, the model of attack on DRPE can be converted to the model of ptyehographical imaging. Owing to the inherent merits of the ptyehographical imaging, the DRPE system can be breached totally in a fast and nearly perfect way, which is unavailable for currently existing attack methods. Further, since the decryption keys can be seen as an object to be imaged from the perspective of imaging, the ptychographical technique may be a kind of new direction to further analysis of the security of other encryption systems based on double random keys.

An encryption scheme based on phase-shifting digital holography and amplitude-phase disturbance

In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.

A new distribution scheme of decryption keys used in optical verification system with multiple-wavelength information

A new distribution scheme of decryption keys used in optical verification systems is proposed. The encryption procedure is digitally implemented with the use of an iteration algorithm in computer. Three target images corresponding to three wavelengths are encoded into three sets of phase-only masks （POMs） by a special distributing method. These three sets of POMs are assigned to three authorized users as the personal identification. A lensless optical system is used as the verification system. In the verification procedure, every two of the three authorized users can pass the verification procedure cooperatively, but only one user cannot do. Numerical simulation shows that the proposed distribution scheme of decryption keys not only can improve the security level of verification system, but also can bring convenience and flexibility for authorized users.

Secure and Robust Optical Multi-Stage Medical Image Cryptosystem

Due to the rapid growth of telemedicine and healthcare services,color medical image security applications have been expanded precipitously.In this paper,an asymmetric PTFrFT(Phase Truncated Fractional Fourier Transform)-based color medical image cryptosystem is suggested.Two different phases in the fractional Fourier and output planes are provided as deciphering keys.Accordingly,the ciphering keys will not be employed for the deciphering procedure.Thus,the introduced PTFrFT algorithm comprises asymmetric ciphering and deciphering processes in contrast to the traditional optical symmetric OSH(Optical Scanning Holography)and DRPE(Double Random Phase Encoding)algorithms.One of the principal impacts of the introduced asymmetric cryptosystem is that it eliminates the onedimensionality aspects of the related symmetric cryptosystems due to its remarkable feature of phase nonlinear truncation components.More comparisons on various colormedical images are examined and analyzed to substantiate the cryptosystem efficacy.The achieved experimental outcomes ensure that the introduced cryptosystem is robust and secure.It has terrific cryptography performance compared to conventional cryptography algorithms,even in the presence of noise and severe channel attacks.

Deep-learning-based cryptanalysis of two types of nonlinear optical cryptosystems

The two types of nonlinear optical cryptosystems(NOCs)that are respectively based on amplitude-phase retrieval algorithm(APRA)and phase retrieval algorithm(PRA)have attracted a lot of attention due to their unique mechanism of encryption process and remarkable ability to resist common attacks.In this paper,the securities of the two types of NOCs are evaluated by using a deep-learning(DL)method,where an end-to-end densely connected convolutional network(DenseNet)model for cryptanalysis is developed.The proposed DL-based method is able to retrieve unknown plaintexts from the given ciphertexts by using the trained DenseNet model without prior knowledge of any public or private key.The results of numerical experiments with the DenseNet model clearly demonstrate the validity and good performance of the proposed the DL-based attack on NOCs.

Opto-Video Encryption Based on Logistic Adjusted Sine map in FrFT

In the last few years,videos became the most common form of information transmitted over the internet,and a lot of the traffic is confidential and must be protected and delivered safely to its intended users.This introduces the challenges of presenting encryption systems that can encode videos securely and efficiently at the same time.This paper presents an efficient opto-video encryption system using Logistic Adjusted Sine map(LASM)in the Fractional Fourier Transform(FrFT).In the presented opto-video LASM-based FrFT scheme,the encoded video is split into distinct frames and transformed into optical signals utilizing an optical supply.Each of the developed optical video frames is ciphered by utilizing the LASM in optical FrFT system using two-phase modulation forms on the video frame,the first in the time-domain and the second in the FrFT domain.In the end,the ciphervideo frame is spotted utilizing a CCD digital camera and transformed into a digital structure that can be managed using a computer.We test the proposed opto-video LASM-based FrFT scheme using various security tools.The outcomes demonstrate that the presented scheme can effectively encrypt and decrypt video signals.In addition,it encrypts videos with a high level of encryption qualitywithout sacrificing its resistance to noise immunity.Finally,the test outcomes demonstrate that the presented scheme is immune to known attacks.

Printable microlaser arrays with programmable modes for information encryption

Lasing emissions with multiple and tunable modes are promising in coding field as a novel cryptographic primitive.With the advantages of simple fabrication,full-color and high-quality-factor whispering gallery mode lasing inside a circular cross-section,polymer microfibers are attractive for photonic devices.However,polymer lasing microfibers for information encryption have never been reported.Herein,we propose a design of printable lasing microfiber encryption chip by in-situ tuning the effective refractive index of the microresonator arrays via a facile approach.Through inkjet printing high-refractive-index nanoparticles on the designated position of lasing microfiber arrays,the effective refractive index of the microcavities is regulated,and the ratio of wavenumber spacing between transverse electric and transverse magnetic mode to the free spectral range can be modulated,particularly with neglectable influence by the size factor.Thus,the programmable region selective encoding process can be conducted simply by a printing program within several minutes.Besides,the encoded microfiber arrays are encapsulated into polydimethylsiloxane to reduce the scattering loss and environmental interference,and a printable encryption chip is realized.This work is expected to provide a platform for the printable encrypted devices.

Cascaded metasurface for separated information encryption[Invited]

For a conventional cascaded metasurface,the combination channel and each single channel are mutually dependent because the phase modulation of a cascaded metasurface is the sum of each single one.Here we propose a cascaded metasurface that can independently encode information into multiple channels.Based on the orientation degeneracy of anisotropic metasurfaces,each single metasurface can produce a quick-response(QR)image in the near field,governed by the Malus law,while the combined channel can produce a holographic image in the far field,governed by geometric phase.The independent and physically separated trichannel design makes information encryption safer.

The Possibility of Applying Spectral Redundancy in Coherent DWDM Systems for Increasing the Data Transmission Rate and Decreasing Nonlinear Effects and Double Rayleigh Scattering with Great Security of Data

A new method coherent DWDM system has been proposed. Standard method uses 90 wavelengths with channel capacity 100 G, so total capacity amounts to 9 Terabit, optical power is P. New “channel super” (CS) consists of 15 wavelengths, number of CS is 6, so total number of wavelengths is 90 too, total capacity is 6 Terabit, but optical power is 4/15P. Over ULH and EULH markets, standard approach will be forced to reduce the total capacity to 2.4 Terabit with optical power 4/15P as in proposed method. But the new can reach 6 Terabit with the same optical power 4/15P.

Image encryption using spatial nonlinear optics

Optical technologies have been widely used in information security owing to its parallel and high-speed processing capability.However,the most critical problem with current optical encryption techniques is that the cyphertext is linearly related with the plaintext,leading to the possibility that one can crack the system by solving a set of linear equations with only two cyphertext from the same encryption machine.Many efforts have been taken in the last decade to resolve the linearity issue,but none of these offers a true nonlinear solution.Inspired by the recent advance in spatial nonlinear optics,here we demonstrate a true nonlinear optical encryption technique.We show that,owing to the self-phase modulation effect of the photorefractive crystal,the proposed nonlinear optical image encryption technique is robust against the known plaintext attack based on phase retrieval.This opens up a new avenue for optical encryption in the spatial nonlinear domain.

Wavelength and polarization dual-multiplexed imaging based on holographic metasurfaces

In light of the powerful light manipulation ability of holographic metasurfaces,optical imaging with wavelength multiplexing and polarization multiplexing is performed in this paper.The metasurface is composed of identical rectangular nanoholes etched in silver film.Three imaging effects,including the in-plane color imaging,three-dimensional wavelength-encrypted imaging,and polarization-multiplexing wavelength-encrypted imaging,are realized.The designed metasurface has compact structure,and the obtained image has lower noise.The simulation and experiment results give the verification.Multiple images,including spatial multiplexing,wavelength multiplexing,and polarization multiplexing,exhibit immense potentialities of metasurfaces,and this work is helpful for expanding the applications of metasurfaces.

全无机二维钙钛矿Cs2PbI2Cl2中的光致相变和光致变色

有机-无机杂化二维ruddlesden-popper(RP)钙钛矿因为其优异的光电性能和良好的稳定性,在太阳能电池和发光器件领域应用前景巨大,而受到广泛关注.最近,人们提出一类新型的二维RP相全无机钙钛矿Cs2PbI2Cl2材料,这类材料具有优异的激子吸收性能以及良好的环境和热稳定性.本文报道了Cs2PbI2Cl2中有趣的光致相变和光致变色现象.在低功率连续激光激发下,Cs2PbI2Cl2的室温光致发光以412 nm处的微弱的紫色发射为主.有趣的是,随着激发功率的增加,发射颜色逐渐由紫色变为明亮的红色.这种光致变色起源于Cs2P b I2C l2晶体内由热能驱动的光致相变而形成的CsPbI3纳米晶.由于Cs2PbI2Cl2基体微晶的保护作用,内嵌的CsPbI3纳米晶的稳定性相比于纯的CsPbI3有明显提高.而具有光致变色特征的Cs2PbI2Cl2可能会在光学加密中得到应用,这在本项工作中得到了初步证实.

Secret key exchange in ultralong lasers by radiofrequency spectrum coding

We propose a new approach to the generation of an alphabet for secret key exchange relying on small variations in the cavity length of an ultralong fiber laser.This new concept is supported by experimental results showing how the radiofrequency spectrum of the laser can be exploited as a carrier to exchange information.The test bench for our proof of principle is a 50-km-long fiber laser linking two users,Alice and Bob,where each user can randomly add an extra 1-km-long segment of fiber.The choice of laser length is driven by two independent random binary values,which makes such length become itself a random variable.The security of key exchange is ensured whenever the two independent random choices lead to the same laser length and,hence,to the same free spectral range.