DWT versus WP Based Optical Color Image Encryption Robust to Composite Attacks

Intensive studies have been done to get robust encryption algorithms. Due to the importance of image information, image encryption has become played a vital rule in information security. Many image encryption schemes have been proposed but most of them suffer from poor robustness against severe types of attacks. In this paper two proposed techniques will be presented for color image encryption to be robust to severe attacks: composite attack. One of these approaches is represented by hybrid use of both steganography and Discrete Wavelet Transform (DWT) based encryption and the other one in which Fractional Fast Fourier Transform (FRFFT) has been used with DWT. Not only new techniques will be presented but also a new chaotic map has been used as random keys for both algorithms. After extensive comparative study with some traditional techniques, it has been found that the proposed algorithms have achieved better performance.

Most of existing optical color image encryption schemes have born security risks due to the adoption of linear transform, and data redundancy for the generation of complex image. To settle these problems effectively, a self-adaptive scheme for double color-image encryption is proposed in this paper. In this scheme, each RGB color component of two secret color images is first compressed and encrypted by 2D compressive sensing (CS) in which measurement matrices are generated by compound chaotic systems. Then, the two measured images are regarded as the real part and imaginary part, constituting a complex image to reduce data redundancy caused by following optical encryption. In the end, the complex image is reencrypted by self-adaptive random phase encoding and discrete fractional random transform (DFrRT) to obtain the final encrypted data. In the process of DFrRT and random phase encoding, the correlations between R, G, B components are adequately utilized. The production of key streams not only depends on the initial value but also on plain-text, and the three color components affect each other to enhance the ability against the known plaintext attack. The projection neural network algorithm is adopted to obtain the decryption images. Simulation results also verify the validity and security of the proposed method.

With the rapid development of computer network technology, information security has attracted increasing attention. Due to the characteristics of multi-dimensional operation and parallel processing capability, optical image encryption techniques have been receiving more and more attention. Since the well-known double random phase encoding technique was proposed, many other methods based on optical information processing means such as the use of optical transform, interference, and polarized light encoding, have been proposed for optical image encryption. However, recent researches have demonstrated that traditional optical encryption techniques are symmetric cryptosystems, in which decryption keys are identical to encryption keys and they have been found to be vulnerable to different types of attacks, such as known plaintext and chosen plaintext attacks. To overcome this shortcoming, asymmetric cryptosystems based on nonlinear phase-truncation techniques and phase retrieval algorithm have been proposed. Asymmetric cryptosystem is a cryptographic system in which encryption keys are different from decryption keys. The encryption keys are used as public keys which are disseminated widely, and the decryption keys are used as private keys which are known only to the authorized users. So, asymmetric cryptosystem can offer a higher-level security than symmetric cryptosystem. However, asymmetric cryptosystems based on phase retrieval algorithms require a lot of computational time, and asymmetric cryptosystems based on phase-truncated Fourier transforms have been found to be vulnerable to special attack. Therefore, in this paper, a novel asymmetric image encryption method is proposed by using the gyrator transform and vector operation. The original image is encrypted into two phase masks with vector operation. One is a random phase mask and the other is a phase mask related to the original image. In the encryption process, the random phase mask is used as a phase key and the other phase mask is transformed by gyrator transform. The transform result is performed by Fourier transform after being modulated by a phase distribution. The ciphertext is the amplitude of the above result. Compared with previous encryption schemes, the suggested method has two advantages. Firstly, we have proposed a new asymmetric encryption method based on the gyrator transform and vector operation. The decryption process is different from the encryption process. The gyrator transform and Fourier transform are used in the encryption process, while only the inverse operation of Fourier transform is employed in the decryption process. In addition, the decryption keys produced in the encryption process are different from the encryption keys. Therefore, the proposed scheme has high resistance against the conventional attacks. Secondly, the encrypted result is real-valued, which is convenient for display, transmission and storage.Numerical simulations illustrate the feasibility and effectiveness of the proposed encryption scheme.

High-efficiency optical image authentication scheme based on ghost imaging and block processing

Metasurface‐enabled full‐polarization vectorial holography has attracted numerous attention due to the promising applications for multichannel displays, enhanced information capacity, and optical encryption. However, recently showcased design strategies suffer from undesirable cross‐talk resulting from interleaved meta‐atoms and are restricted to a two‐dimensional plane. This work presents a general approach for full‐polarization beam shaping in three‐dimensional space by completely exploiting the capacity of a noninterleaved metasurface. The noninterleaved metasurface is spin‐decoupled, which is capable of achieving independent phase control for the two orthogonal circular polarizations by combining both propagation and geometric phases. As a proof‐of‐concept, a three‐dimensional vectorial holography capable of converting the linear polarized light to holographic images with arbitrary spatial polarization distributions is experimentally demonstrated. Taking use of the extended dimension, the z‐axis distance, which provides a new degree of flexibility for boosting information capacity and security, a double‐level optical encryption scheme is implemented. This work provides a compact and general scheme for full‐polarization channel wavefront steering, unlocking a new door for designing planar polarization functionality devices.

This paper deals with the application of Spatial and Temporal DWT (Discrete Wavelet transform) on the videos. Here we will discuss about three mechanisms and their performance on videos at increased DWT level. In any video processing algorithm, memory is the major criteria. In these three mechanisms dynamic (automatic) DWT level selection and manual level selection is implemented. Here we will also discuss about implementation of different DWT level in spatial and temporal domain. In this paper Haar wavelet is taken as the reference as it has its inherent properties and ease of implementation.

A novel optical double-image encryption scheme based on Gaussian apertured reality-preserving fractional Mellin transform (GARPFrMT) is proposed. In terms of optical image encryption, GARPFrMT has several attractive advantages: (1) The GAPRFrMT can be used to scramble the value of two images simultaneously; (2) GARPFrMT is constructed in diffraction domain to ensure that the ciphertext is real; (3) Owing to the nonlinearity, this transform can ensure that the proposed encryption system can be kept from the potential insecurity; and (4) A Gaussian lens is applied to improve intensity distributions of the output light. Experimental results demonstrate that the proposed algorithm is feasible and robust by a lot of attack analysis, i.e. sensitivity attack analysis (>99.60%), differential attack analysis (NPCR >99.6072 and UACI >33.5681%), entropy values (almost 7.99928), statistical attack (correlation coefficient values are almost 0), noise attack, cropping attack and NIST analysis.

Face recognition is a significant biometric credential in the field of security authentication. It additionally assumes a noteworthy job in image processing and it is applicable in various systems like verifying the identity of the person and in security purpose. Recognizing the face with varying background, poses and illumination are the complexity involved in this face recognition. Many algorithms exist for face recognition, of which, Discrete Wavelet Transform (DWT) with Principal Component Analysis (PCA) works better for recognition of faces. An algorithm using 3 Level-DWT and modified PCA is proposed for feature extraction. The PCA and reconstruction of images using Inverse PCA, help not only for dimensionality reduction, but also to find the least principal components (PC) of an image from which the significant features of a face image can be extracted. The significant features thus extracted are used for classifying genetic and non-genetic faces. Using extracted features from 3 level DWT and PCA, Support vector machine (SVM) is utilized to classify the faces genetically. The proposed extracted features does not intend to certain features like ears, nose and eyes of the face, but corresponds to identify the faces which are genetically similar. Based on the statistical measure analysis, the proposed algorithm 3 Level dwt with modified PCA works well in extracting the features for identifying the faces which are genetically closer. This face recognition application system can be effectively used to treat a patient in other location with complete security. There is no chance for data stealing, since the concerned doctors and patient only will take part in the system. The identification of genetic faces will turn out to be an achievement in the field of health care monitoring systems.

Optical encryption scheme for multiple-image based on spatially angular multiplexing and computer generated hologram

Full Poincaré beams, which cover all polarization states on the Poincaré sphere, provide a unique and complete degree of freedom for polarization manipulation in optical encryption. This paper introduces a novel optical image encryption method based on double random phase encoding (DRPE) system with multi-dimensional keys of full Poincaré beam. The encryption process begins by preprocessing the full Poincaré beam with a polarizer, followed by loading the image to be encrypted along this polarization direction, and finally performing encryption via the DRPE system. The scheme integrates conventional optical keys, such as wavelength, topological charge, amplitude, and phase, with the complete polarization dimension afforded by the full Poincaré beam, as well as the spatial loading dimension of the image placed behind the lens. By synergistically combining these multi-dimensional keys, the encryption system significantly expands the key space. Additionally, the dual random phase modulation capability of the DRPE system further enhances information security. This work establishes a new paradigm for high-security optical encryption.

Double optical image encryption using discrete Chirikov standard map and chaos-based fractional random transform

It was suggested that spectrum estimation can be accomplished by applying wavelet denoising methodology to wavelet packet coefficients derived from the logarithm of a spectrum estimate. The particular algorithm we consider consists of computing the logarithm of the multitaper spectrum estimator, applying an orthonormal transform derived from a wavelet packet tree to the log multitaper spectrum ordinates, thresholding the empirical wavelet packet coefficients, and then inverting the transform. For a small number of tapers, suitable transforms/partitions for the logarithm of the multitaper spectrum estimator are derived using a method matched to statistical thresholding properties. The partitions thus derived starting from different stationary time series are all similar and easily derived, and any differences between the wavelet packet and discrete wavelet transform (DWT) approaches are minimal. For a larger number of tapers, where the chosen parameters satisfy the conditions of a proven theorem, the simple DWT again emerges as appropriate. Hence, using our approach to thresholding and the method of partitioning, we conclude that the DWT approach is a very adequate wavelet-based approach and that the use of wavelet packets is unnecessary.

In conventional symmetric encryption, it is common for the encryption/decryption key to be reused for multiple plaintexts. This gives rise to the concept of a known-plaintext attack. In optical image encryption systems, such as double random phase encoding (DRPE), this is also the case. With optical encryption, if one knows a plaintext-ciphertext pair, one can carry out a known-plaintext attack more efficiently than a bruteforce attack, using heuristics based on phase retrieval or simulated annealing. However, it is more likely that an attacker will find an imperfect encryption/decryption key using such heuristics. Such an imperfect key will work for the known plaintext-ciphertext pair, but not an arbitrary unseen plaintext-ciphertext pair using the original key. In this paper, we illustrate the problem and attempt to characterise the increase in security it affords optical encryption.

A new method of three-dimensional (3D) image optical encryption based on phase-shifting compressive Fresnel holography (PSCFH) is presented. In the optical encryption step, the 3D object is encrypted with random phase masks using phase-shifting interferometry to record three intensity images with different phase-shifting. In the decryption step, the three-step phase-shifting technique is first used to extract the complex optical field at the recording plane. Finally, the 3D object is reconstructed from the recovered complex optical field using compressive Fresnel holography with the correct key. Numerical experiments demonstrate the feasibility and robustness of our proposed PSCFH method.

The paper presents an opto-double color image cipher using two dimensional (2D) chaotic Arnold transform (AT) as a preprocessing scrambling stage and 2D chaotic Logistic adjusted Sine map (LASM) phase masks in the Fresnel (Fr)-based Hartley Transform (HT). In the proposed opto-double color image cipher, the 2D chaotic LASM is utilized to create chaotic phase masks. The color plainimage red, green and blue channels are firstly scrambled with 2D chaotic AT. Then, the scrambled color plainimage red, green and blue R-G-B channels are modulated using the 2D chaotic LASM phase mask and transformed with the Fr-based HT. The transformed complex R-G-B channels distributions are secondly scrambled with the 2D chaotic AT, modulated secondly with the 2D chaotic LASM phase mask and transformed with Fr-based HT. The utilization of 2D chaotic LASM phase masks in addition to the 2D chaotic AT provides efficient key administration and communication. Also, optical geometric parameters are considered as extra additional keys that enhances the secrecy of the proposed scheme. A comprehensive security study is employed for the proposed scheme and test results verifies and ensures that the proposed scheme is highly immune and resistant against most potential attacks.