Chaos-based Image Cryptosystems Research Articles

PSDCLS: Parallel simultaneous diffusion–confusion image cryptosystem based on Latin square

Today, due to the unparalleled growth of multimedia data sharing, especially digital images, between users over insecure channels in real-time applications, cryptography algorithms have gained increasing attention for the secure and efficient transmission. In classical chaos-based image cryptosystems, the confusion and diffusion operations are often applied as two separate and independent phases, which threatens the cryptosystem security. To address these problems, in this paper, a fast image cryptosystem based on parallel simultaneous diffusion–confusion strategy has been proposed using Latin squares, called PSDCLS. It consists of three main steps. First, the initial parameters of the Hénon-Sine chaotic map are produced from SHA256 of both the plain image content and the user’s secret key. Second, a chaos-based random Latin square is constructed by employing the chaotic sequence produced through the Hénon-Sine chaotic map. Third, a parallel simultaneous diffusion–confusion scheme is proposed by using Latin square and vectorization technique to overcome the problems of computational complexity and high risk of separable and iterative confusion–diffusion operations in the classical chaos-based image cryptosystems. To analyze and evaluate the security and performance of PSDCLS cryptosystem, we conducted extensive simulations and experiments on various benchmark images. Experimental results and analyses show that PSDCLS achieves excellent scores for information entropy (>7.99), correlation coefficients close to 0, key space (2512), NPCR (>99.60%), UACI (>33.46%). The encryption time for test images of size 512 × 512 and 512×512×3 was around 0.026 and 0.081 s, respectively. Therefore, PSDCLS is highly robust against common cryptographic attacks and serves as a swift cryptosystem for real-time encryption applications. The source code of PSDCLS is accessible at: https://github.com/EbrahimZarei64/PSDCLS.

Proposed 3D chaos-based medical image cryptosystem for secure cloud-IoMT eHealth communication services

Proposed 3D chaos-based medical image cryptosystem for secure cloud-IoMT eHealth communication services

Design and DSP implementation of a fractional-order detuned laser hyperchaotic circuit with applications in image encryption

In this paper, a fractional-order hyperchaotic detuned laser system (FHDLS) is proposed, and a novel image cryptosystem with high-security performance is designed by combining FHDLS, improved shuffling algorithm, and DNA mutation diffusion algorithm. Firstly, the complex dynamics of FHDLS is researched by phase diagram, bifurcation diagram, Lyapunov exponential spectrum, and spectral entropy (SE) complexity. The attractor coexistence phenomenon of the system is analyzed from different initial values for given parameters. Meanwhile, the randomness of the proposed FHDLS is verified by the correlation. Then, the FHDLS is implemented by the analog circuit and the digital hardware (Digital Signal Processing, DSP), respectively. Finally, make use of these excellent characteristics, and perturb the initial values and chaotic state of the system through Secure Hash Algorithm 256 (SHA-256). Then the pixel-level and bit-level replacement and transformation operations are performed on the image respectively, to implement a chaos-based image cryptosystem. The regimen performs one scrambled and diffusion together and one diffusion operation to achieve maximum confusion and diffusion. To demonstrate the safety performance of the proposed image cryptographic regimen, standard security analyses is adopted, including histogram, correlation, information entropy, security key, anti-differential attack, robustness, etc., and it is compared with the existing advanced algorithms. The experimental results indicate that the regimen works well in encryption and can resist various attacks effectively, and the FHDLS has wide application prospects in image encryption.

Designing a double-way spread permutation framework utilizing chaos and S-box for symmetric image encryption

Recently, many chaos-based image cryptosystems have been investigated. However, some drawbacks of existing schemes are as follows: (1) the high computational complexity and bad scrambling effect of permutation algorithm reduce the security and practicality of the encryption system; (2) the insufficient association between encryption algorithm and plaintext makes it suffer from low plaintext sensitivity and inability to effectively resist chosen plaintext attack; (3) some algorithms are one-time-pad-like encryption systems, which reduce their practical value; (4) adequate plaintext relation elevates the plaintext sensitivity but also increases the ciphertext sensitivity of a cryptosystem and make it possess low robustness of defending noise and data loss attacks. To address the defects of existing works, a symmetric plaintext-related image cryptosystem based on a new scrambling framework using S-box is proposed. Firstly, substitution-box(S-box) of AES is first used to develop a new scrambling framework, namely double-way spread permutation framework (DWSPF), which can be used to scramble color images and gray images of any size. Then, the present study develops a new method of plaintext association that one parameter carried the information of original image and used to control the encryption process is padded to the encrypted array which is transmitted to the receiver. Such a strategy can realize the sufficient plaintext relation without the use of one-time-pad encryption technology and avoid high ciphertext sensitivity, which can well resist noise attacks and information loss attacks. Sufficient experiments results demonstrate that the proposed permutation framework and cryptosystem possess excellent security and efficiency compared with the state-of-art works.

SELECTIVE CHAOTIC GENERATION AND MULTI-MODALITY DIGITAL IMAGE CRYPTO SYSTEM USING HAAR WAVELETS

The importance of secured image transmission plays a significant role in this information era. The hackers hack the medical data in the form of images that costs more in terms of claiming insurances. It is necessary to secure the images that cannot be accessed by the unauthorized persons. Among the many types of image crypto systems, the chaos based image crypto systems is best known for its key insensitive to attack or hacking. The properties of the chaos play a major role in the generation of key for the secured transmission and reception. The Haar wavelet transform is yet simpler transform used to compress the input image in terms of approximate and detailed coefficients. The incorporation of the key in the approximate coefficients of the input image provides an efficient encryption when compared to other image crypto schemes. The encryption quality is evaluated using the histogram analysis of the encrypted of cipher image with different keys generated using respective chaotic maps. The framed image crypto system is designed and simulated using MATLAB software package. KEYWORDS: image cryptosystems, chaos theory, Haar wavelet transform, encryption, key generation.

Efficient Chaos-Based Substitution-Box and Its Application to Image Encryption

Chaotic systems are vital in designing contemporary cryptographic systems. This study proposes an innovative method for constructing an effective substitution box using a 3-dimensional chaotic map. Moreover, bouyed by the efficiency of the proposed chaos-based substitution boxes’ effectiveness, we introduce a new chaos-based image cryptosystem that combines the adeptness of Gray codes, a non-linear and sensitive hyper-chaotic system, and the proposed S-box. The generated secret key emanating from the cryptosystem is correlated to the input image to produce a unique key for each image. Extensive experimental outcomes demonstrate the utility, effectiveness, and high performance of the resulting cryptosystem.

Investigation of Chaotic Image Encryption in Spatial and FrFT Domains for Cybersecurity Applications

The need for cybersecurity increases to protect the exchange of information for improving the data privacy. This paper presents an investigation of the encryption efficiency of the chaotic-based image block ciphering in the spatial and Fractional Fourier Transform (FrFT) domains. The main aim of this investigation is to examine the efficiency of different chaotic maps, while considering the parameters of the FrFT as additional keys for encryption and achieving reliable cybersecurity for robust image communication. In this paper, Cat, Baker, and Logistic map confusion approaches are applied in the spatial and FrFT domains to study and analyze the cybersecurity and ciphering efficiency of chaos-based image cryptosystems. The confusion features of the chaotic maps in spatial and FrFT domains are investigated using information entropy, differential analysis, histograms, visual observation, attack analysis, impact of noise, and encryption quality tests. Simulation results prove that the chaotic-based image encryption in the FrFT domain increases the efficiency of the confusion process and achieves a high nonlinear relation between the plainimage and the cipherimage in a symmetric ciphering approach. Moreover, the results demonstrate that the Cat-FrFT scheme is more susceptible to channel noise attacks than the Baker-FrFT and the Logistic-FrFT schemes. Hence, they can be implemented efficiently in the scenarios of noisy channels due to their high robustness to channel noise.

Suggested Integral Analysis for Chaos-Based Image Cryptosystems.

Currently, chaos-based cryptosystems are being proposed in the literature to provide confidentiality for digital images, since the diffusion effect in the Advance Encryption Standard (AES) algorithm is weak. Security is the most important challenge to assess in cryptosystems according to the National Institute of Standard and Technology (NIST), then cost and performance, and finally algorithm and implementation. Recent chaos-based image encryption algorithms present basic security analysis, which could make them insecure for some applications. In this paper, we suggest an integral analysis framework related to comprehensive security analysis, cost and performance, and the algorithm and implementation for chaos-based image cryptosystems. The proposed guideline based on 20 analysis points can assist new cryptographic designers to present an integral analysis of new algorithms. Future comparisons of new schemes can be more consistent in terms of security and efficiency. In addition, we present aspects regarding digital chaos implementation, chaos validation, and key definition to improve the security of the overall cryptosystem. The suggested guideline does not guarantee security, and it does not intend to limit the liberty to implement new analysis. However, it provides for the first time in the literature a solid basis about integral analysis for chaos-based image cryptosystems as an effective approach to improve security.

A Simple Chaotic Map-Based Image Encryption System Using Both Plaintext Related Permutation and Diffusion.

Recently, to conquer most non-plain related chaos-based image cryptosystems’ security flaws that cannot resist the powerful chosen/knownn plain-text attacks or differential attacks efficiently for less plaintext sensitivity, many plain related chaos-based image cryptosystems have been developed. Most cryptosystems that have adopted the traditional permutation–diffusion structure still have some drawbacks and security flaws: (1) most plaintext related image encryption schemes using only plaintext related confusion operation or only plaintext related diffusion operation relate to plaintext inadequately that cannot achieve high plaintext sensitivity; (2) in some algorithms, the generation of security key that needs to be sent to the receiver is determined by the original image, so these algorithms may not applicable to real-time image encryption; (3) most plaintext related image encryption schemes have less efficiency because more than one round permutation–diffusion operation is required to achieve high security. To obtain high security and efficiency, a simple chaotic based color image encryption system by using both plaintext related permutation and diffusion is presented in this paper. In our cryptosystem, the values of the parameters of cat map used in permutation stage are related to plain image and the parameters of cat map are also influenced by the diffusion operation. Thus, both the permutation stage and diffusion stage are related to plain images, which can obtain high key sensitivity and plaintext sensitivity to resist chosen/known plaintext attacks or differential attacks efficiently. Furthermore, only one round of plaintext related permutation and diffusion operation is performed to process the original image to obtain cipher image. Thus, the proposed scheme has high efficiency. Complete simulations are given and the simulation results prove the excellent security and efficiency of the proposed scheme.

A Robust Chaos-Based Image Cryptosystem with an Improved Key Generator and Plain Image Sensitivity Mechanism

In this paper, we propose an effective gray image cryptosystem containing Arnold cat map for pixel permutation and an improved Logistic map for the generation of encryption keys to be used for pixel modification. Firstly, a new chaotic map is designed to show better performance than the standard one in terms of key space range, complexity and uniformity. Generated secret key is not only sensitive to the control parameters and initial condition of the improved map but also strongly depend on the plain image characteristic which provides an effective resistance against statistical and differential attacks. Additionally, to get higher encryption strength of the cryptosystem, both confusion and diffusion processes are performed with different keys in every iterations. Theoretical analysis and simulation results confirm that the proposed algorithm has superior security and effectively encrypts and decrypts the gray images as well.

Hyperchaotic dynamical system based image encryption scheme with time-varying delays

In this paper, we propose a 4D chaotic image encryption technique based on a dynamic state variables selection mechanism to improve the effectiveness and security of chaos-based image cryptosystems. Experimental outcomes of our scheme demonstrate better security against many known attacks, as well as high efficiency.

A new image cryptosystem based on 2D hyper-chaotic system

An efficient image encryption scheme is designed based on 2D hyper-chaotic system. Different from the traditional chaos-based image encryption schemes, the confusion and the diffusion procedures of the proposed scheme are interacted on each other. In the encryption process, the position of the present pixel is influenced by the last diffused one. Then the corresponding diffused pixel makes a difference in the next pixel. By contrast with the traditional chaos-based image cryptosystems, the proposed cryptosystem with the interacted structure is steadier and harder to decipher. In addition, 2D hyper-chaotic systems are employed in the quicker generation of chaotic sequences in comparison to high-dimensional hyper-chaotic systems. Simulation results verify the security and effectiveness of this scheme.

A new color image encryption scheme using CML and a fractional-order chaotic system.

The chaos-based image cryptosystems have been widely investigated in recent years to provide real-time encryption and transmission. In this paper, a novel color image encryption algorithm by using coupled-map lattices (CML) and a fractional-order chaotic system is proposed to enhance the security and robustness of the encryption algorithms with a permutation-diffusion structure. To make the encryption procedure more confusing and complex, an image division-shuffling process is put forward, where the plain-image is first divided into four sub-images, and then the position of the pixels in the whole image is shuffled. In order to generate initial conditions and parameters of two chaotic systems, a 280-bit long external secret key is employed. The key space analysis, various statistical analysis, information entropy analysis, differential analysis and key sensitivity analysis are introduced to test the security of the new image encryption algorithm. The cryptosystem speed is analyzed and tested as well. Experimental results confirm that, in comparison to other image encryption schemes, the new algorithm has higher security and is fast for practical image encryption. Moreover, an extensive tolerance analysis of some common image processing operations such as noise adding, cropping, JPEG compression, rotation, brightening and darkening, has been performed on the proposed image encryption technique. Corresponding results reveal that the proposed image encryption method has good robustness against some image processing operations and geometric attacks.

Fingerprint image cryptography based on multiple chaotic systems

This paper presents a new multiple chaos-based biometric image cryptosystem for fingerprint security. This encryption algorithm is constructed with four chaotic systems, which consist of two 1-D and two high-dimensional 3-D chaotic systems. This algorithm enhances the security strength of biometric image cryptography that incorporates single chaos and multiple 1-D chaotic systems. The advantage of the proposed scheme is that it possesses a secret key space large enough to empower the security strength to protect fingerprint image, which is enough to prevent any brute-force attacks. Furthermore, this algorithm has passed the NIST SP 800-22a tests and security analyses, which confirms that the proposed scheme is a secure cryptographic system.

A METHOD FOR IMAGE ENCRYPTION BASED ON FRACTIONAL-ORDER HYPERCHAOTIC SYSTEMS

By using sequences generated from fractional-order hyperchaotic systems, a color image encryption scheme is investigated. Firstly, a plain image, which is known to users in advance, is chosen as a secret key to confuse the original image. Then, the confused image is encrypted by the sequences generated from the fractional-order hyperchaotic systems. With this simple encryption method, we can get an encrypted image that is fully scrambled and diused. For chaos-based image cryptosystems, this encryption scheme enhances the security and improves the eectiveness. Furthermore, the cryptosystem resists the dierential attack. Experiments show that the algorithm is suitable for image encryption, and some statistical tests are provided to show the high security in the end

An efficient image encryption scheme using gray code based permutation approach

In recent years, the operation efficiency of chaos-based image cryptosystems has drawn much more concerns. However, the workload arised from floating point arithmetic in chaotic map iteration prevents the efficiency promotion of these cryptosystems. In this paper, we present a novel image encryption scheme using Gray code based permutation approach. The new permutation strategy takes full advantage of (n, p, k)-Gray-code achievements, and is performed with high efficiency. A plain pixel-related image diffusion scheme is introduced to compose a complete cryptosystem. Simulations and extensive security analyses have been carried out and the results demonstrate the high security and operation efficiency of the proposed scheme.

A chaos-based image encryption scheme using 2D rectangular transform and dependent substitution

Chaos-based image cryptosystems usually adopt the traditional confusion-diffusion architecture which is considered insecure against known/chosen plaintext attacks. To overcome this drawback, this paper proposes a novel chaos-based image encryption scheme, in which the two-dimensional rectangular transform is employed to directly scramble the image of any rectangular size, and the dependent substitution is introduced to substitute for each pixel according to the image pixels. This scheme comprises two stages of encryption processes. Each stage provides the confusion and diffusion simultaneously in one traverse of image pixels. As a result, the proposed scheme has high speed and achieves a satisfactory security performance. Experimental results and various types of security analysis indicate that this scheme is efficient and secure enough to be used for practical image encryption and transmission.

A fast chaos-based image encryption scheme with a dynamic state variables selection mechanism

In recent years, a variety of chaos-based image cryptosystems have been investigated to meet the increasing demand for real-time secure image transmission. Most of them are based on permutation–diffusion architecture, in which permutation and diffusion are two independent procedures with fixed control parameters. This property results in two flaws. (1) At least two chaotic state variables are required for encrypting one plain pixel, in permutation and diffusion stages respectively. Chaotic state variables produced with high computation complexity are not sufficiently used. (2) The key stream solely depends on the secret key, and hence the cryptosystem is vulnerable against known/chosen-plaintext attacks. In this paper, a fast chaos-based image encryption scheme with a dynamic state variables selection mechanism is proposed to enhance the security and promote the efficiency of chaos-based image cryptosystems. Experimental simulations and extensive cryptanalysis have been carried out and the results prove the superior security and high efficiency of the scheme.

A fast chaos-based symmetric image cryptosystem with an improved diffusion scheme

In recent years, a number of chaos-based image cryptosystems have been proposed to meet the increasing demand for real-time secure image transmission. In this paper, an improved diffusion scheme named continuous diffusion strategy is proposed to promote the efficiency of the conventional permutation–diffusion type image cipher. The new scheme contains a supplementary diffusion procedure after the conventional diffusion process and the control parameters are altered by the cipher image after the first diffusion procedure. As a result, the difference can be introduced at the beginning and spread out to the whole image, and hence the same level of security can be achieved with fewer overall rounds. Moreover, to further enhance the confusion effect of the diffusion operation, an intensive diffusion approach is proposed, using stretched key stream elements to perform a cyclic shift to the cipher pixels. Extensive cryptanalysis has been performed using differential analysis, key space analysis, key sensitivity analysis and various statistical analyses. Experiment results demonstrate that the new scheme has a high level of security and fast encryption speed for practical image encryption.

An asymmetric image cryptosystem based on the adaptive synchronization of an uncertain unified chaotic system and a cellular neural network

Chaotic dynamics provide a fast and simple means to create an excellent image cryptosystem, because it is extremely sensitive to initial conditions and system parameters, pseudorandomness, and non-periodicity. However, most chaos-based image encryption schemes are symmetric cryptographic techniques, which have been proven to be more vulnerable, compared to an asymmetric cryptosystem. This paper develops an asymmetric image cryptosystem, based on the adaptive synchronization of two different chaotic systems, namely a unified chaotic system and a cellular neural network. An adaptive controller with parameter update laws is formulated, using the Lyapunov stability theory, to asymptotically synchronize the two chaotic systems. The synchronization controller is embedded in the image cryptosystem and generates a pair of asymmetric keys, for image encryption and decryption. Using numerical simulations, three sets of experiments are conducted to evaluate the feasibility and reliability of the proposed chaos-based image cryptosystem.