Occlusion Attacks Research Articles

A New Composite Fractal Function and Its Application in Image Encryption.

Fractal’s spatially nonuniform phenomena and chaotic nature highlight the function utilization in fractal cryptographic applications. This paper proposes a new composite fractal function (CFF) that combines two different Mandelbrot set (MS) functions with one control parameter. The CFF simulation results demonstrate that the given map has high initial value sensitivity, complex structure, wider chaotic region, and more complicated dynamical behavior. By considering the chaotic properties of a fractal, an image encryption algorithm using a fractal-based pixel permutation and substitution is proposed. The process starts by scrambling the plain image pixel positions using the Henon map so that an intruder fails to obtain the original image even after deducing the standard confusion-diffusion process. The permutation phase uses a Z-scanned random fractal matrix to shuffle the scrambled image pixel. Further, two different fractal sequences of complex numbers are generated using the same function i.e. CFF. The complex sequences are thus modified to a double datatype matrix and used to diffuse the scrambled pixels in a row-wise and column-wise manner, separately. Security and performance analysis results confirm the reliability, high-security level, and robustness of the proposed algorithm against various attacks, including brute-force attack, known/chosen-plaintext attack, differential attack, and occlusion attack.

Colour-image encryption based on 2D discrete wavelet transform and 3D logistic chaotic map

This paper proposes a new lossless encryption and decryption method for digital colour-image using 2D discrete Haar wavelet transform (DHWT) and 3D logistic chaotic map. The proposed cryptosystem provides the security of the digital images using the cryptographic algorithm in the frequency domain of the image. The proposed method uses two levels of 2D DHWT for the decomposition of the image. For the encryption, 2D DHWT is applied on the different colour components of the colour-image and then the encryption method is applied on the different sub-bands of each level of decomposition and for the decryption the reverse process of the encryption is used with the inverse of functions used in encryption. The experimental results and the security analysis like brute force analysis, statistical analysis, occlusion and differential attack of the proposed method are given to validate the feasibility and robustness of the method.

An asymmetric image encryption mechanism using QR decomposition in hybrid multi-resolution wavelet domain

In this paper, an asymmetric image encryption mechanism using QR decomposition technique in hybrid multi-resolution wavelet (HMW) domain is presented. QR decomposition technique utilized here makes the system asymmetric, as the obtained permutation matrix serves as ciphertext and the product of orthogonal and triangular matrices act as decryption keys. It also enables compression as the ciphertext obtained through QR decomposition is a sparse matrix which can be stored using CSR method. The HMW is obtained by utilizing existing orthogonal transforms: Walsh transform and fractional Fourier transform (frFT). Here the fractional orders of fractional Fourier transform (frFT) matrices are employed here to generate HMW, which function as supplementary keys. Therefore, they enhance the key space and strengthen the proposed system. The proposed encryption system exhibits non-linearity and enlarged key-space to dodge any brute-force attack. Computer-based simulations have been carried out on the grayscale images to verify and validate the proposed encryption mechanism. And the results obtained clearly demonstrate the robustness of the proposed mechanism against occlusion and noise attacks.

Triple color image encryption based on 2D multiple parameter fractional discrete Fourier transform and 3D Arnold transform

This paper proposes a new encryption and decryption method for triple color images using 2D multiple parameter fractional discrete Fourier transform (MPFrDFT) and 3D Arnold transform (AT). The proposed method converts three color images into Bayer images, which are considered as the three components of a color image. These three Bayer images are combined vertically and then baker chaotic map is applied to permute rows and columns and a similar process is applied in the horizontal combination, the image then obtained is considered as the complex valued image (CVI). Then apply 2D MPFrDFT on this CVI. The output of 2D MPFrDFT is separated into three components. Apply 3D AT into the three components and the output is considered as the three color components of the encrypted image. The experimental results and the security analysis of the proposed method are given to validate the feasibility and robustness of the method. The statistical analyses like histogram, correlation and entropy confirm the robustness of the proposed method against statistical attacks and experimental results show that the method is resistant to occlusion attack. The mathematical analysis shows that the brute force attack is not possible in proposed method.

Optical image encryption based on biometric keys and singular value decomposition.

We propose an asymmetric optical image cryptosystem based on biometric keys and singular value decomposition (SVD) in the Fresnel transform domain. In the proposed cryptosystem, the biometric keys are palmprint phase mask generated by a palmprint, a chaotic phase mask, and an amplitude truncated Fourier transform, which can provide the cryptosystem with more data security due to the uniqueness of the palmprint. Two images are first encoded into a complex function, which then is modulated by the palmprint phase mask. A Fresnel transform and then an SVD operation are performed on the modulated result. The SVD operation is used to generate private secret keys, which makes the encryption secret keys and decryption secret keys different, and thus the encryption process and decryption process are different. In addition, multiple images are encrypted into a real-valued ciphertext, making it convenient to transport and record. Numerical simulation results have demonstrated that our proposed encryption system has robustness against statistical, occlusion, noise, and chosen-plaintext attacks.

Double image encryption using 3D Lorenz chaotic system, 2D non-separable linear canonical transform and QR decomposition

In this paper, a double image encryption scheme using 3D Lorenz chaotic system and QR decomposition in 2D non-separable linear canonical transform domain is proposed. Here the independent parameters of the 2D non-separable canonical transform enlarge the key-space of the proposed scheme and enhance robustness against brute-force attack. 3D Lorenz chaotic system is employed for creating a permutation keystream for pixel transaction process. The proposed scheme is non-linear and asymmetric in nature. To validate and verify the proposed cryptosystem, the numerical simulations have been performed on grayscale images. Results display that the proposed scheme has greater robustness to occlusion and special attacks.

Fast and Efficient Image Encryption Algorithm Based on Modular Addition and SPD.

Bit-level and pixel-level methods are two classifications for image encryption, which describe the smallest processing elements manipulated in diffusion and permutation respectively. Most pixel-level permutation methods merely alter the positions of pixels, resulting in similar histograms for the original and permuted images. Bit-level permutation methods, however, have the ability to change the histogram of the image, but are usually not preferred due to their time-consuming nature, which is owed to bit-level computation, unlike that of other permutation techniques. In this paper, we introduce a new image encryption algorithm which uses binary bit-plane scrambling and an SPD diffusion technique for the bit-planes of a plain image, based on a card game trick. Integer values of the hexadecimal key SHA-512 are also used, along with the adaptive block-based modular addition of pixels to encrypt the images. To prove the first-rate encryption performance of our proposed algorithm, security analyses are provided in this paper. Simulations and other results confirmed the robustness of the proposed image encryption algorithm against many well-known attacks; in particular, brute-force attacks, known/chosen plain text attacks, occlusion attacks, differential attacks, and gray value difference attacks, among others.

An Image Encryption Scheme Based on DNA Computing and Multiple Chaotic Systems

A number of techniques for securing plaintext, images and video frames have been developed in cryptography using jointly DNA computing and Chaos Theory. With the advancement of DNA/quantum computing, the threats of security breaches to information have an increasing possibility. In this paper, we propose a symmetric encryption algorithm for color images by extending the current encryption/decryption techniques. Our encryption algorithm is based on three chaotic systems (PWLCM, Lorenz and 4D Lorenz-type), a Secure Hash Algorithm, a scrambler, a chaotic generator and DNA sequence based Linear Feedback Shift Register. We introduce multilevel security to increase the degree of diffusion and confusion. Through experiments, we present security analysis for key irreproducibility and sensitivity, Gray Level Co-occurrence Matrix based analysis, maximum deviation, irregular deviation, entropy, histogram, variance and correlation, number of pixel change rate, unified average cipher intensity, known/chosen-plaintext attacks, mean absolute error, robustness against noises of various types using PSNR and occlusion attacks. It is demonstrated that mostly our proposed encryption algorithm has enhanced performance as compared to contemporary works in information security, while comparable in other cases.

3C3R, an Image Encryption Algorithm Based on BBI, 2D-CA, and SM-DNA

Color image encryption has enticed a lot of attention in recent years. Many authors proposed a chaotic system-based encryption algorithms for that purpose. However, due to the shortcomings of the low dimensional chaotic systems, similar rule structure for RGB channels, and the small keyspace, many of those were cryptanalyzed by chosen-plaintext or other well-known attacks. A Security vulnerability exists because of the same method being applied over the RGB channels. This paper aims to introduce a new three-channel three rules (3C3R) image encryption algorithm along with two novel mathematical models for DNA rule generator and bit inversion. A different rule structure was applied in the different RGB-channels. In the R-channel, a novel Block-based Bit Inversion (BBI) is introduced, in the G-channel Von-Neumann (VN) and Rotated Von-Neumann (RVN)- based 2D-cellular structure is applied. In the B-channel, a novel bidirectional State Machine-based DNA rule generator (SM-DNA) is introduced. Simulations and results show that the proposed 3C3R encryption algorithm is robust against all well-known attacks particularly for the known-plaintext attacks, statistical attacks, brute-force attacks, differential attacks, and occlusion attacks, etc. Also, unlike earlier encryption algorithms, the 3C3R has no security vulnerability.

A cloud compatible DNA coded security solution for multimedia file sharing & storage

The faster proliferation of software-defined cloud environments across the world for efficiently hosting enterprise-grade applications has led many organisations to embrace the cloud paradigm in a significant way. The cloud storage opportunities and possibilities are consistently expanding, wherein multimedia storage occupies the entire stage in the cloud. An essential emphasis on security owing to the nature of multiuser access to cloud credentials in many situations is necessary. The security and safety of data, while in transit, in rest, and while being used by applications, have to be guaranteed through proven technology solutions. Typically, image encryption is the standard way of securing and safeguarding images. The proposed three-layer image encryption scheme uses DNA coding along with chaotic logistic and tent maps for confusion and diffusion operations. Upon verification of user credentials, the storage of encrypted image is accomplished in Amazon S3 web services. The strength of encryption has been evaluated based on the parameters namely brute force attack, statistical, encryption quality, occlusion attack and computational complexity analyses which have proved the suitability of proposed scheme to secure cloud storage of images.

Entropy-Based Block Scrambling Image Encryption Using DES Structure and Chaotic Systems

Traditional encryption algorithms are inefficient when applied to image encryption because image data have the characteristics of large data sizes and strong correlations between adjacent pixels. The shortcomings of the traditional Data encryption standard (DES) encryption algorithm when applied to image encryption are analyzed, and a new image encryption algorithm based on the traditional DES encryption algorithm model, chaotic systems, DNA computing, and select cipher-text output is proposed. Select cipher-text output selects cipher image with the biggest entropy, and it can increase the randomness of cipher image and reduce the risk of encryption system being broken down. This algorithm overcomes the shortcomings of high computational complexity and inconvenient key management that the traditional text encryption algorithm has when applied to image encryption. The experimental results show that the security of this algorithm is verified by analyzing the information entropy, image correlation of adjacent pixels and other indexes. At the same time, this algorithm passes the noise attack test and the occlusion attack test, so it can resist common attacks.

A New Algorithm for Medical Color Images Encryption Using Chaotic Systems.

In this paper, we present a new algorithm based on chaotic systems to protect medical images against attacks. The proposed algorithm has two main parts: A high-speed permutation process and adaptive diffusion. After the implementation of the algorithm in the MATLAB software, it is observed that the algorithm is effective and appropriate. Also, to quantitatively evaluate the uniformity of the histogram, the chi-square test is done. Key sensitivity analysis demonstrates that images cannot be decrypted whenever a small change happens in the key, which indicates that the algorithm is suitable. Clearly, part of special images is selected to test the selected plain-text, like an all-white image and an all-black image. Entropy results obtained from the implementation of the algorithm on this type of images show that the proposed method is suitable for this particular type of images. In addition, the obtained results from noise and occlusion attacks analysis show that the proposed algorithm can withstand against these types of attacks. Moreover, it can be seen that the images after encryption and decryption are of good quality; the measures such as the correlation coefficients, the entropy, the number of pixel change rate (NPCR), and the uniform average change intensity (UACI) have suitable values; and the method is better than previous methods.

Security enrichment of optical image cryptosystem based on superposition technique using fractional Hartley and gyrator transform domains deploying equal modulus decomposition

In this paper, a symmetric cryptosystem has been suggested to increase security of double random phase encoding using superposition technique in fractional Hartley transform (FrHT) and gyrator transform (GT) domains. It uses structured phase mask (SPM) and hybrid mask (HM) deploying equal modulus decomposition (EMD). Related to original phase truncated Fourier transform (PTFT) based cryptosystem, the security of encoding and decoding is upgraded by using the superposition technique. With the usage of SPM we can increase the key space while encoding and can also overcome the axis alignment difficulty. Decoding is just the reversal of the encoding method. The proposed scheme has robustness against common attacks like: noise and occlusion attacks. With the help of numerical simulation results we also show that our cryptosystem is vulnerable to various attacks. Performance of the suggested method is calculated in terms of Mean Square Error (MSE) between original and decoded image and also the sensitivity of the SPM parameters and rotational angles of GT is investigated. The competence of the suggested method includes analysis on EMD, histogram and correlation coefficient. The suggested cryptosystem is also open to the occlusion attack and noise attack to analyze its performance and evenness.

An asymmetric hybrid cryptosystem using hyperchaotic system and random decomposition in hybrid multi resolution wavelet domain

In this paper, an asymmetric hybrid cryptosystem utilizing four-dimensional (4D) hyperchaotic framework by means of coherent superposition and random decomposition in hybrid multi-resolution wavelet domain is put forward. The 4D hyperchaotic framework is utilized for creating permutation keystream for a pixel swapping procedure. The hybrid multi-resolution wavelet is formed by combining Walsh transform and fractional Fourier transform of various orders. The 4D hyperchaotic framework’s parameters and preliminary conditions alongside the fractional orders extend the key-space and consequently give additional strength to the proposed cryptosystem. The proposed cryptosystem has an extended key-space to avoid any brute-force attack and is nonlinear in nature. The scheme is validated on greyscale images. Computer-based simulations have been executed to validate the robustness of the proposed scheme against different types of attacks. Results demonstrate that the proposed cryptosystem along with offering higher protection against noise and occlusion attacks is also unassailable to special attack.

Optical image hiding under framework of computational ghost imaging based on an expansion strategy.

A novel optical image hiding scheme based on an expansion strategy is presented under the framework of computational ghost imaging. The image to be hidden is concealed into an expanded interim with the same size as the host image. This is implemented by rearranging the measured intensities of the original object after the process of ghost imaging. An initial Hadamard matrix is used to generate additional matrices by shifting it circularly along the column direction, so that enough 2D patterns are engendered to retrieve phase-only profiles for imaging. Next, the frequency coefficients of the host image are modified with that of the expanded interim by controlling a small weighting factor. After an inverse transform, the host image carrying the hidden information can be obtained with high imperceptibility. Security is assured by considering optical parameters, such as wavelength and axial distance, as secret keys due to their high sensitivity to tiny change. Importantly, differing from other computational ghost imaging based schemes, many phase-only profiles are used to collect the measured intensities to enhance the resistance against noise and occlusion attacks. The simulated experiments illustrate the feasibility and effectiveness of the proposed scheme.

A Spiral-Phase Rear Mounted Triple Masking for Secure Optical Image Encryption Based on Gyrator Transform

Background: A spiral phase rear mounted masked scheme is proposed based on Gyrator Transform (GT) to enhance the security contribution of second lens of the existing Double Random Phase Encoding (DRPE) system by modulating the phase of the output obtained in output plane. An additional third layer of Spiral Phase Mask (SPM) is included in the output plane in the same 4f system. Objective: To develop a symmetric cryptosystems to enhance the security potential of the second lens and to prevent the comfortable realization of the cipher-image in the transform domain. Methods: The original image is first scrambled using Arnold transform with frequency and then is convoluted with a secret random phase mask, RPM in GT and then obtained result is convoluted with another secret RPM in inverse GT. The obtained result is then finally convoluted with SPM. Results: It verifies the sensitivity and achieves better performance in terms of recovering a high quality image. Results show the security, performance and quality analysis on the basis of correlation coefficient, occlusion attack, key sensitivity and noise attack, entropy and histogram. Conclusion: It enhances the security potential of second lens in DRPE and introduces diffusion in the system. The system is simulated for binary and greyscale image and achieves better performance as compared to existing DRPE variants. Key sensitivity is more secure and cannot recover original image without knowing all the parameters. Correlation coefficient are also weakly correlated and does not reveals relevant information. Simulation result demonstrates the feasibility and robustness of cryptosystem.

Deep Learning for Improving the Robustness of Image Encryption

In this paper, we propose a method to increase the robustness of 2D/3D optical image encryption using the dilated deep convolutional neural network (CNN). In order to solve the problem that encrypted images suffer from some attacks in practical application, we utilize a fast and effective CNN denoiser based on the principle of deep learning. The CNN improves the robustness of the algorithm by improving the resolution of the reconstructed images. Besides, CNN has a high performance against blur and occlusion attacks. We introduce the pixel scrambling method to enhance the security level of the encryption by the private key of pixel scrambling operation. The proposed method can not only realize the encryption of a two-dimensional image but also implement three-dimensional image encryption by combining the integral imaging technology. Double random phase encoding in the fractional Fourier domain is selected for experimental verification, and the results show the capability for robustness, noise immunity, and security of the proposed method.

Optical image encryption using gamma distribution phase masks in the gyrator domain

BackgroundOptical information encryption technology has received extensive attention from researchers in recent years because of its advantages of parallel and high-speed processing capability, as well as the controllability of phase components.MethodsAn encryption method for grayscale images with a pair of random phase masks based on gamma distribution in the gyrator domain is proposed. In this scheme, two random distribution phase-images using random parameters according to the definition of the gamma probability distribution function are generated. They are loaded onto spatial light modulators as random phase masks used in the encryption process. The input grayscale image transmitted through the first random phase mask. And then they are encoded by the first gyrator transform. The resulting information is again encrypted by a second gamma distribution random phase mask at the gyrator frequency plane. The final results are encoded by the second gyrator transform.ResultsNumerical simulations are presented to confirm the security, validity, and flexibility of the proposed idea. The gyrator transform rotation angle sensitivity test is also simulated. The occlusion and noise attacks analysis establish the scheme’s robustness.ConclusionsIn gyrator transform-based optical image encryption cipher system, encrypting the input image with different parameters of gamma distribution RPMs will significantly change the statistical distribution of phase in the ciphertext. It means that the phase distribution in the ciphertext will not obey the law of random scattering medium. Therefore, it has potential to resist the attack based on the phase retrieval algorithm. Therefore, the security and flexibility of encryption can be improved by using gamma distribution RPMs.

Multiple images encryption method via spiral phase mask rotations under a JTC system

ABSTRACTA method of multiple-image encryption via spiral phase mask rotations based on the joint transform correlator encryption system was proposed. Multiple images can be encrypted into one ciphertext through this approach. When decrypted the ciphertext, we have no need to produce too many key masks, only need rotate the key mask to the angle corresponding to the plaintext. The system also has good resistance to occlusion attack and differential attack. Computer simulations initially verified the correctness of this method, and the experimental results also confirmed its validity further.

System to Safeguard the Identity of Persons in Photographs through Cryptography and Steganography Techniques Using Chaos

Safeguarding the identity of people in photographs or videos published through social networks or television is of great importance to those who do not wish to be recognized. In this paper, a face detecting and coding system is designed with the goal of solving this problem. Mathematical models to generate chaotic orbits are deployed. One of them applies the diffusion technique to scramble the pixels of each face while another implements the confusion technique to alter the relation between plain text and ciphered text. Afterward, another two orbits are utilized for the steganography technique to modify the least significant bit (LSB) to conceal data that would allow authorized users to decipher the faces. To verify the robustness of the proposed encryption algorithm, different tests are performed with the Lena standard image, such as correlation diagrams, histograms, and entropy. In addition, occlusion, noise, and plain image attacks are performed. The results are compared with those of other works, and the proposed system provided high sensitivity at secret key and a large space for the encryption keys, good speed for ciphering, disorder in the cryptogram, security, data integrity, and robustness against different attacks.