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The typical categories of chaotic ciphers are mainly divided into plaintext-independent type and plaintext-related type. Due to the existence of equivalent key in the plaintext-independent type, it can usually be deciphered by simply using chosen-plaintext attacks. Recently, some plaintext-related chaotic ciphers have been proposed for improving the security performance. However, it is found that under the premise of predictability and reconfiguration of plaintext-related quantities, chosen-plaintext/ciphertext attacks can still remain valid. But if the above-mentioned conditions do not hold true, it is not possible for chosen-plaintext/ciphertext attacks to decipher the generalized plaintext-related chaotic ciphers. Therefore, it is necessary for cryptanalysts to discover some new analytical approaches. To further explore the problem, this paper proposes initially the divide-and-conquer attack on this type of plaintext-related chaotic ciphers,and takes the cryptanalysis on the latest similar scheme as an example to illustrate the main idea. Armed with the divide-and-conquer strategy, the related pixels are deciphered firstly. Then, the remainder pixels can also be deciphered followed by the chosen-plaintext attack, difference method, S-box strategy, and removing diffusion effect. Meanwhile, an improved scheme is also given to eliminate potential flaw, which have no need of additional plaintext information for decryption, but also can resist against divide-and-conquer attack. Theoretical analysis and numerical experiments have confirmed the feasibility of the method. [ABSTRACT FROM AUTHOR]

Aiming at addressing the security and efficiency challenges during image transmission, an efficient image cryptosystem utilizing difference matrix and genetic algorithm is proposed in this paper. A difference matrix is a typical combinatorial structure that exhibits properties of discretization and approximate uniformity. It can serve as a pseudo-random sequence, offering various scrambling techniques while occupying a small storage space. The genetic algorithm generates multiple ciphertext images with strong randomness through local crossover and mutation operations, then obtains high-quality ciphertext images through multiple iterations using the optimal preservation strategy. The whole encryption process is divided into three stages: first, the difference matrix is generated; second, it is utilized for initial encryption to ensure that the resulting ciphertext image has relatively good initial randomness; finally, multiple rounds of local genetic operations are used to optimize the output. The proposed cryptosystem is demonstrated to be effective and robust through simulation experiments and statistical analyses, highlighting its superiority over other existing algorithms. [ABSTRACT FROM AUTHOR]

This research introduces an innovative image encryption method that amalgamates two secure and efficient chaotic maps, namely a 2D Simplified Quadratic Polynomial Map (2D-SQPM) and a 2D Symbolic Chaotic Map (2D-SCM), within an enhanced Feistel network structure. The primary motivation for this research is to address the limitations of current image encryption methods that are vulnerable to statistical and differential attacks. A hash function is also integrated to elevate the key’s security and sensitivity. Unlike standard Feistel networks, which split the plaintext into two parts and employ only XOR operations at the bit level, this research’s Feistel Network modification involves dividing the plaintext into four sections and introducing a diverse set of operations, including substitution and permutation at both the bit and byte levels across different parts, thereby optimizing confusion and diffusion effects. The empirical evaluation demonstrates that this method significantly reduces pixel correlation and strengthens encryption against statistical and differential attacks. Supported by various analytical tools like entropy analysis, NPCR, UACI, chi-square, key space and sensitivity analysis, robustness testing, and NIST suite evaluations, the proposed method significantly enhances image encryption performance. In conclusion, the proposed method effectively secures image data and sets a new benchmark in image encryption. The significance of this research lies in its integration of complex, chaotic dynamics and advanced encryption mechanisms, providing a substantial contribution to digital information security.

Encryption systems play a vital role in the transfer of sensitive data, and the integration of chaotic systems into this domain has garnered significant attention. However, these systems often grapple with complexity and insufficient security, posing challenges for real-world implementation. Researchers introduced the synchronization techniques to fix these problems, which means making sure that the chaotic systems in both the transmitter and receiver systems behave in a way that can be understood so that accurate signal recovery can happen. Chaotic system synchronisation presents challenges and security risks besides the limited of the encryption keys make them subjected to attacks. Because of their advantages over traditional chaotic systems in terms of flexibility, adaptability, and computational efficiency, artificial neural networks, or ANNs, are being used more and more to study chaotic systems. This paper presents NeuroChaosCrypt, a novel cryptographic framework employing unique methodologies for secure data transmission. It utilizes an Artificial Neural Network (ANN)-based chaotic system at both transmitter and receiver, eliminating the need for synchronization. A comprehensive case study, including audio signal transmission, underscores NeuroChaosCrypt’s efficacy. Comparison with a traditional encryption system integrating a Linear Quadratic Regulator (LQR) controller reveals comparable security levels, correlation coefficient (cc), Signal-to-Noise Ratio (SNR), Peak-to-Root Mean Square Distortion (PRD), and encryption time. NeuroChaosCrypt, enhanced by ANNs, excels in decryption speed, key-space coverage, and hardware implementation using field-programmable gate arrays (FPGAs). This methodology achieves a higher maximum frequency while requiring fewer logic units. The comparison offers valuable insights into audio encryption methods, aiding informed decision-making for selecting the most suitable solution based on specific application requirements. Finally, we introduce an application of the proposed NeuroChaosCrypt for image encryption to ensure that the study can exploit other data types for broader applicability.

Aiming at addressing the security and efficiency challenges during image transmission, an efficient image cryptosystem utilizing difference matrix and genetic algorithm is proposed in this paper. A difference matrix is a typical combinatorial structure that exhibits properties of discretization and approximate uniformity. It can serve as a pseudo-random sequence, offering various scrambling techniques while occupying a small storage space. The genetic algorithm generates multiple ciphertext images with strong randomness through local crossover and mutation operations, then obtains high-quality ciphertext images through multiple iterations using the optimal preservation strategy. The whole encryption process is divided into three stages: first, the difference matrix is generated; second, it is utilized for initial encryption to ensure that the resulting ciphertext image has relatively good initial randomness; finally, multiple rounds of local genetic operations are used to optimize the output. The proposed cryptosystem is demonstrated to be effective and robust through simulation experiments and statistical analyses, highlighting its superiority over other existing algorithms.

This work proposes a novel image encryption algorithm that integrates unique image transformation techniques with the principles of chaotic and hyper-chaotic systems. By harnessing the unpredictable behavior of the Chua system and the hyper-chaotic nature of the Chen system, the algorithm carries out rescaling, rotation, and randomization on the target image. The intrinsic unpredictability and sensitivity to initial conditions of these chaotic systems endow the encryption algorithm with an expansive key space of 25208. This feature not only bolsters its resilience against brute-force attacks but also magnifies its overall security profile. The algorithm’s efficiency is evident in its rapid computational speed and lean resource consumption, making it suitable for real-time applications. To gauge its robustness, a battery of rigorous tests and analyses, spanning differential attacks, statistical attacks, and brute-force assaults, were employed. The results validate its ability to resist a diverse spectrum of threats. With its expansive key space, exceptional efficiency, and sturdy defenses, the proposed algorithm emerges as a potential cornerstone for safeguarding digital images in arenas like secure communication, data storage, and multimedia transmission. In sum, this research pushes the boundaries of high-security image encryption methodologies, catering to the burgeoning demands of the digital age.

With the proliferation of digital images over open networks, secure and efficient encryption schemes are imperative for safeguarding image privacy. This paper proposes a novel 5-stage image encryption algorithm adhering to Shannon’s confusion and diffusion paradigm. In the first stage, Langton’s Ant is employed to induce chaos and perturb the pixel distribution of the original image. The second and fourth stages apply Mersenne Twister generated keys to confuse the image via XOR operations. An S-box substitution is utilized in the third stage to disrupt pixel statistical properties. Finally, Arnold’s Cat map further scrambles and diffuses the pixel positions over the image. Extensive security analyses reveal the algorithm’s robustness against various attacks such as visual, entropy, brute-force, statistical and differential attacks. Additionally, it successfully passes the NIST SP 800–22 test suite. Performance results demonstrate the proposed algorithm’s efficacy for real-time secure image transmission with low computational overheads. The algorithm’s security level combined with high-speed performance makes it well-suited for practical image encryption applications.

With advancements in computer and communication technologies, the production, utilization and applications of digital images is at an unprecedented rate. Recent applications include military communications, remote sensing, novel engineering designs storage and communications, as well as medical imaging. In most cases, such images convey highly sensitive or confidential information, which creates a strong need for the design of secure and robust color image cryptosystems. Recent literature has shown that fractional-order functions exhibit improved performance over their corresponding integer-order versions. This is especially true in their use in image processing applications. In this research work, we make use of a four-dimensional (4D) hyperchaotic Chen map of fractional-order, in conjunction with a sine chaotic map and a novel hybrid DNA coding algorithm. A thorough numerical analysis is presented, showcasing the security performance and efficiency of the proposed color image cryptosystem. Performance is gauged in terms of resilience against visual, histogram, statistical, entropy, differential, as well as brute-force attacks. Mean values of the metrics computed are as follows. MSE of 9396, PSNR of 8.27 dB, information entropy of 7.997, adjacent pixel correlation coefficient of 0, NPCR of 99.62%, UACI of 33, MAE of 80.57, and a very large key space of 2744. The proposed image cryptosystem exhibits low computational complexity, as it encrypts images at a rate of 4.369 Mbps. Furthermore, it passes the NIST SP 800 suite of tests successfully. Comparison of the computed metrics of the proposed image cryptosystem against those reported in the state-of-the-art by counterpart algorithms show that the proposed cryptosystem exhibits comparable or superior values.

Image encryption is essential to keep images secure either in personal devices or over the cloud drives. Various robust image cryptosystems have been implemented during the past decades to keep the encrypted images far from illegal decryption by eavesdroppers. Biological sequences contain high density information that introduce new challenges and opportunities to traditional cryptography. This article presents a novel image cryptosystem, namely Image-to-Protein (I2P), that is based on successively encoding the image pixels into sequences of symbols analogous biological DNA and Protein sequences, and then scrambling these sequences into frequent and non-frequent patterns which in turn are binary encoded into the encrypted file. The proposed cryptosystem has been applied on experimental grayscale and color images. The large key space and the complicated Protein encoding operations guaranteed resistance to many known cryptographic attacks. Furthermore, the biological encoding of the plain image pixels resulted in high similarity that achieved noticeable lossless compression when compressed using known text compression techniques.

Abstract Cloud computing plays a vital task in our daily lives, in which an enormous amount of data is stored daily on cloud storage. The highest priority for cloud data storage is guaranteeing the security of confidential data. The security of confidential data can be realised through utilising one of the cryptographic mechanisms including encryption and data hiding. With the rapid development for the realization of quantum computers, modern cryptosystems may be cracked including cloud systems. Accordingly, it is a crucial task for achieving confidentiality of data stored on cloud storage before the availability of quantum computers. Therefore, this study aims to utilise one of the quantum computational models, as a quantum-inspired system, to layout a new data confidentiality technique that can be applied in digital devices to have the capability for resisting the potential attacks from quantum and digital computers. In this paper, a new image security algorithm for real-time cloud applications using Gray code, quantum walks (QW), and Henon map is proposed. In the proposed image cryptosystem, the generated key streams from QW and Henon map is related to the plain image with high sensitivity of slight bit changes on the plain image. The outcomes based on deep analysis proves that the presented algorithm is efficient with high security for real-time application.

In recent years, establishing secure visual communications has turned into one of the essential problems for security engineers and researchers. However, only limited novel solutions are provided for image encryption, and limiting visual cryptography to only limited schemes can bring up negative consequences, especially with emerging quantum computational systems. This paper presents a novel algorithm for establishing secure private visual communication. The proposed method has a layered architecture with several cohesive components, and corresponded with an NP-hard problem, despite its symmetric structure. This two-step technique is not limited to gray-scale pictures, and furthermore, it is relatively secure from the theoretical dimension.

Cloud computing plays a vital task in our daily lives, in which an enormous amount of data is stored daily on cloud storage. The highest priority for cloud data storage is guaranteeing the security of confidential data. The security of confidential data can be realised through utilising one of the cryptographic mechanisms including encryption and data hiding. With the rapid development for the realization of quantum computers, modern cryptosystems may be cracked including cloud systems. Accordingly, it is a crucial task for achieving confidentiality of data stored on cloud storage before the availability of quantum computers. Therefore, this study aims to utilise one of the quantum computational models, as a quantum-inspired system, to layout a new data confidentiality technique that can be applied in digital devices to have the capability for resisting the potential attacks from quantum and digital computers. In this paper, a new image security algorithm for real-time cloud applications using Gray code, quantum walks (QW), and Henon map is proposed. In the proposed image cryptosystem, the generated key streams from QW and Henon map is related to the plain image with high sensitivity of slight bit changes on the plain image. The outcomes based on deep analysis proves that the presented algorithm is efficient with high security for real-time application. [ABSTRACT FROM AUTHOR]

Confusion and diffusion are two main concepts in cryptography that affect the quality of encryption and resistance to various attacks. Both of these concepts are influenced by the quality of the keystream used. Keystream generation needs to involve plain images as one way to bind sensitivity to plain images. But when it involves plain images directly, encryption security has negative side effects. So this research proposes to perform a diffusion operation with a logistic map on a plain image before generating the keystream. Not only using one keystream, the proposed method also uses three other keystreams and Arnold transform whose input parameters are processed by hash operations. Two keystreams are generated using the four-dimensional Lorenz system for the permutation of column and row image pixels. Next, sixteen Arnold transforms with different parameters are used for bit permutation. The last keystream is generated with a Henon map to carry out the diffusion stage two so that a cipher image is produced. Based on the testing results, the proposed method has satisfactory encryption results that are resistant to various attacks, especially brute force, statistical, and differential attacks.

The security system engaged to transfer securely the sensitive information over wireless channels must posses some innate features such as high resistivity to various cryptographic attacks, high sensitivity to secret key and plaintext, and strong statistical characteristics of encrypted content. Recently, an image cryptosystem is investigated to secure color images while transmission. The cryptosystem is based on permutation only cipher and employed synchronized 4D hyperchaotic systems. The cryptosystem has credibility of providing ample statistical encryption quality of ciphertext. This paper aims to investigate and analyze the security of this image cryptosystem in terms of its defects and attack resistivity. The security analysis uncovers that cryptosystem holds certain serious security defects and incapable to secure encrypted content. To support the claim, the inherent defects are highlighted; thereby an attack procedure is proposed to show that the cryptosystem is breakable under the proposed cryptanalysis. The attacker can recover complete plaintext image from ciphertext image without knowing secret key. Computer simulations are performed to justify the success of cryptanalysis. The image cryptosystem is all insecure for use in practical applications of image-based secure wireless communication. As a remedy, this paper also suggests security enhancements and an enhanced cryptosystem is proposed to make it completely resistive against above and other types of cryptanalytic attacks and increase on its plain image sensitivity and statistical encryption strength.

To address the shortcomings of weak confusion and high time complexity of the existing permutation algorithms, including the traditional Josephus ring permutation (TJRP), an improved Josephus ring-based permutation (IJRBP) algorithm is developed. The proposed IJRBP replaces the remove operation used in TJRP with the position exchange operation and employs random permutation steps instead of fixed steps, which can offer a better scrambling effect and a higher permutation efficiency, compared with various scrambling methods. Then, a new encryption algorithm based on the IJRBP and chaotic system is developed. In our scheme, the plaintext feature parameter, which is related to the plaintext and a random sequence generated by a chaotic system, is used as the shift step of the circular shift operation to generate the diffusion matrix, which means that a minor change in the source image will generate a totally different encrypted image. Such a strategy strikes a balance between plaintext sensitivity and ciphertext sensitivity to obtain the ability to resist chosen-plaintext attacks (CPAs) and the high robustness of resisting noise attacks and data loss. Simulation results demonstrate that the proposed image cryptosystem has the advantages of great encryption efficiency and the ability to resist various common attacks. [ABSTRACT FROM AUTHOR]

This paper devotes to the image compression and encryption problems. We develop a novel hybrid scheme based on block compressive sensing. Concentrate on taking full advantage of the different frequency coefficients sparsity, the nonuniform sampling strategy is adopted to improve the compression efficiency. First, the discrete cosine transform coefficients matrices of blocks are transformed into vectors by zigzag scanning. The different frequency components are extracted in the front, middle, and back of vectors, respectively. Using the measurement matrices with different dimensions, the combination of low- and high-frequency components, together with the medium-frequency coefficients are compressed simultaneously. Second, the recombinational block measurements are re-encrypted by the permutation-diffusion framework. The logistic map is introduced for key stream generation. In order to accomplish a sensitive and effective cryptosystem, the control strategy for secret keys is employed. The simulation results indicate that the proposed scheme forms a high balance between reconstruction performance, storage and computational complexity, and hardware implementation. Moreover, the security analyses demonstrate the satisfactory performance and effectiveness of the proposed cryptosystem. The scheme can work efficiently in the parallel computing environment, especially for the images with medium and large size.

The security system engaged to transfer securely the sensitive information over wireless channels must posses some innate features such as high resistivity to various cryptographic attacks, high sensitivity to secret key and plaintext, and strong statistical characteristics of encrypted content. Recently, an image cryptosystem is investigated to secure color images while transmission. The cryptosystem is based on permutation only cipher and employed synchronized 4D hyperchaotic systems. The cryptosystem has credibility of providing ample statistical encryption quality of ciphertext. This paper aims to investigate and analyze the security of this image cryptosystem in terms of its defects and attack resistivity. The security analysis uncovers that cryptosystem holds certain serious security defects and incapable to secure encrypted content. To support the claim, the inherent defects are highlighted; thereby an attack procedure is proposed to show that the cryptosystem is breakable under the proposed cryptanalysis. The attacker can recover complete plaintext image from ciphertext image without knowing secret key. Computer simulations are performed to justify the success of cryptanalysis. The image cryptosystem is all insecure for use in practical applications of image-based secure wireless communication. As a remedy, this paper also suggests security enhancements and an enhanced cryptosystem is proposed to make it completely resistive against above and other types of cryptanalytic attacks and increase on its plain image sensitivity and statistical encryption strength. [ABSTRACT FROM AUTHOR]

Abstract Chaos-based image encryption schemes shuffle the position of the pixels (confuse), change their values (diffuse), to camouflage the identity of the original image. In this paper, a symmetric image cryptosystem based on permutation is proposed. Permutation, used both to change the position of the pixel and modify its value, is undertaken using the Bogdanov map. First, the input image is permuted using the Bogdanov map so that the pixel positions are changed. Thereafter, the resultant scrambled image is sliced into bit-planes which are again separately subjected to the Bogdanov map. The encrypted image is constructed by encrypting the scrambled bit-planes with the key generated using dyadic transform. The experimental results exhibited random behavior in the distribution of the pixel values of the encrypted image. The cryptosystem is simple and fast, as it is permutation-based and, secure, it may be used in real-time transmission.

To address the shortcomings of weak confusion and high time complexity of the existing permutation algorithms, including the traditional Josephus ring permutation (TJRP), an improved Josephus ring-based permutation (IJRBP) algorithm is developed. The proposed IJRBP replaces the remove operation used in TJRP with the position exchange operation and employs random permutation steps instead of fixed steps, which can offer a better scrambling effect and a higher permutation efficiency, compared with various scrambling methods. Then, a new encryption algorithm based on the IJRBP and chaotic system is developed. In our scheme, the plaintext feature parameter, which is related to the plaintext and a random sequence generated by a chaotic system, is used as the shift step of the circular shift operation to generate the diffusion matrix, which means that a minor change in the source image will generate a totally different encrypted image. Such a strategy strikes a balance between plaintext sensitivity and ciphertext sensitivity to obtain the ability to resist chosen-plaintext attacks (CPAs) and the high robustness of resisting noise attacks and data loss. Simulation results demonstrate that the proposed image cryptosystem has the advantages of great encryption efficiency and the ability to resist various common attacks.

In this paper, a new 4D hyperchaotic nonlinear dynamical system with two positive Lyapunov exponents is presented. Exhaustive dynamic analyses of the novel hyperchaotic model using several dynamical studies are described. The dynamics of the system considered are first investigated analytically and numerically to explore phenomena and the selection of hyperchaotic behavior utilized for designing image cryptosystem. Since the proposed hyperchaotic model has rich dynamics, it displays hidden attractors. It emerges from this dynamic the existence of a single unstable equilibrium point giving rise to self-excited attractors, hysteresis phenomenon, and hyperchaotic behavior strongly recommended for securing information by its character. Furthermore, the feasibility and synchronization of the proposed system are also presented by developing, respectively, Raspberry surveys and an adaptive synchronization approach of two identical hyperchaotic systems. By employing the hyperchaotic behavior of the 4D map, an image encryption scheme is proposed as well. It is one round of a pixel-based permutation and a bit-wise diffusion phase. The secret key of the 4D map is derived from the SHA-256 value of the input image. It acts as the signature of the input image. Hence, the secret key exhibits high sensitivity to single-bit alteration in the image, which makes the cryptosystem robust against chosen/known-plaintext attacks. Performance analyses prove that the proposed cryptosystem provides the best in terms of the performance/complexity trade-off, as compared to some recently published algorithms.

Based on orthogonal Latin cubes, an image cryptosystem with confusion–diffusion–confusion cipher architecture has been proposed recently (Inf. Sci.2019, 478, 1–14). However, we find that there are four fatal vulnerabilities in this image cryptosystem, which leave open doors for cryptanalysis. In this paper, we propose a reference-validation inference algorithm and design screening-based rules to efficiently break the image cryptosystem. Compared with an existing cryptanalysis algorithm, the proposed method requires fewer pairs of chosen plain-cipher images, and behaves stably since different keys, positions of chosen bits and contents of plain images will not affect the cryptanalysis performance. Experimental results show that our cryptanalysis algorithm only requires 8×H×W3+3 pairs of chosen plain-cipher images, where H×W represents the image’s resolution. Comparative studies demonstrate effectiveness and superiority of the proposed cryptanalysis algorithm.

In recent years, AES is known as the excellent choice between the existing symmetric cryptosystems to encrypt binary or text data. However, this standard encryption algorithm is unsuitable for images regarding the particular features of these kinds of data such as high correlation, high redundancy, and voluminosity. Based on this fact, we have designed a new cryptosystem taking into account the aforementioned characteristics which provides high performance and security level. Actually, the cryposystem adopts a new structure named Outer-Inner structure. This new structure consists of two phases: Outer phase and Inner phase. In the former phase, the image is treated as a single block. The purpose of this phase is to address the correlation and the redundancy issue of images. In order to ensure the efficiency and to avoid the problem of treating an image as a single block where several image encryption algorithms suffer from it, this phase only involves lightweight operations. In the later phase the image is treated as a set of fixed blocks. The aim of this phase is to address the voluminosity issue. In fact, during this phase each block can be encrypted independently through an iterative function. The experiment results show that 7 rounds are sufficient to reach an acceptable security level. [ABSTRACT FROM AUTHOR]

A novel bit-level image cryptosystem is proposed by introducing a new coupled map lattices (CML). The modified non-adjacent spatiotemporal chaotic system with good dynamic performance is constructed by coupling the piecewise-linear chaotic map (PWLCM) in a non-adjacent manner. In the proposed bit-level image cryptosystem, the binary plain image is scrambled globally by a 2D hyper-chaos system. And the confused image is then diffused via the pseudo-random sequences produced quickly and efficiently from the fabricative CML. After converting the diffused binary matrix into its homologous decimal matrix, the cipher image is achieved. Computer simulations and performance comparisons with recent image encryption algorithms demonstrate the superior performance and high security of our proposed cryptosystem. [ABSTRACT FROM AUTHOR]

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This paper cryptanalyses the hyper-chaotic image encryption scheme developed by Norouzi et al. and presents a chosen-plain-image attack scenario to reveal its generated key stream. The recovered key stream can be used to decrypt any future related cipher-image without having the secret key. In addition, the paper introduces an advanced version of the underlying image encryption scheme to overcome its security shortcomings. Specifically, the proposed cipher generates a unique key stream for each distinct plain-image based on its fingerprint. This thwarts the chosen-plain-image attacks and enhances the security level of the proposed scheme. Finally, the experimental results confirm the robustness of the proposed image cipher against different types of attacks. [ABSTRACT FROM AUTHOR]

With the advent of multimedia technology and rapid data transmission ability of networks, images have become a vital source of extracting information. So its security becomes a critical issue. Images are encrypted to another form in order to preserve their data. In this paper, we have put forward a hybridized model for encrypting images through a combination of Genetic Algorithm and DNA Sequence. DNA sequence is basically chosen as it offers greater storage and higher computing capabilities. The encryption method consists of two phases- Transposition or Scrambling phase and Substitution phase. In the first phase, pixel locations are altered using GA to reduce the correlation among adjacent pixels. In substitution phase, the pixels are replaced by using XOR operation between the pixel values converted into binary strings and DNA substrings derived from a random DNA string. DNA substrings are used as keys for image encryption. The experimental outcome validates that the algorithm is simple, fast enough and feasible. Performance analysis asserts the robustness of the algorithm against all kinds of attacks and thereby maintaining higher security. [ABSTRACT FROM AUTHOR]

This paper presents a cryptanalysis of a recent proposed image encryption technique based on neural chaotic generator. In this algorithm, the permutation at the pixel level is used to shuffle the position of image pixels. Moreover, to confuse the relationship between cipher-image and plain-image, a permutation process at bits level of pixels is performed. However, by applying chosen plaintext attack which is described in this paper, we show that the cryptosystem is not robust to resist chosen-plaintext attack. As a conclusion, the use of this image cryptosystem is not recommended in secure communications. [ABSTRACT FROM AUTHOR]

By combining chaotic system and DNA sequence operations, an image cryptosystem is proposed. To generate sequences with better chaotic characteristics, a new spatiotemporal chaotic system is constructed by employing the Logistic-Sine system (LSS) in the coupled map lattice (CML). In the cryptosystem, the original image is firstly diffused through exclusive or with a key image transformed from the constructed spatiotemporal chaotic sequences. Furthermore, DNA deletion and DNA insertion pseudo-operations are used to confuse the DNA-encoded diffused image under the control of the key streams. The encrypted image is obtained after decoding the confused DNA image. Experimental results and performance analysis demonstrate that the proposed image cryptosystem has acceptable speed, good robustness and outperforms some existing image encryption schemes to counteract the recognized attacks. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel image cryptosystem, which enables to encrypt the secret images with a smaller-size cover image. Compared with the existing meaningful encryption methods, our cryptosystem has three advantages: (1) non-embedding encryption, i.e., there isn’t any data embedding into the cover image during the encryption process. (2) Our cryptosystem can simultaneously encrypt multiple secret images with one cover image, which greatly improves the security of secret images. (3) Our cryptosystem can accomplish not only the meaningful encryption, but also the meaningless encryption. Thus, people don’t switch encryption methods when meeting different encryption requirements. Our scheme leverages the popular coupled dictionary learning and compressive sensing techniques to accomplish the whole task. Specifically, we use the coupled dictionaries to build connection between the cover image and the secret image, and apply the compressive sensing to decrypt the secret image. To demonstrate the effectiveness of the proposed cryptosystem, a series of experiments are conducted. Experimental results on gray images and colorful RGB images verify its superiority. [ABSTRACT FROM AUTHOR]

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.

This paper investigates the effect of the angle of the Fractional Fourier transform (FrFT) on encryption quality in a chaotic image cryptosystem. The adopted approach for encryption is 2D chaotic Baker map. This map is applied to the transformed images using FrFT with different angles. We inspect its application to digital images and its exhaustive security investigation. The security investigation contains statistical tests like histogram and correlation coefficient, the maximum and the irregular deviation metrics, and the processing time. Experimental results prove that the rotation angle of the FrFT does not affect the encryption quality. This indicates a wide range of angles that can be used in this transform domain for encryption in addition to increasing the scheme sensitivity and making it hard for the attacker to exactly determine the right angle used in the transform domain. [ABSTRACT FROM AUTHOR]

This paper presents an implementation of 2D chaotic Baker map using different modes of operation in the fractional Fourier transform domain on digital images. The proposed image cryptosystem implements the chaotic Baker map scrambling using three different modes of operation: cipher block chain, cipher feedback, and output feedback, in which the initialization vector works as the main key. We examine its implementation for digital images along with its detailed security analysis. The security analysis includes the statistical analysis, the histogram analysis, the correlation coefficient metric, the maximum deviation metric, the irregular deviation metric, the noise immunity, the processing time, and the key space analysis. Experimental results verify and prove that the proposed image cryptosystem is highly secure from the cryptographic viewpoint, more immune to noise, has high key sensitivity, and takes less processing time. [ABSTRACT FROM AUTHOR]

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. • The proposed double-way spread permutation framework utilizing chaos and s-box can be used to scramble color images and gray images of any size and has excellent confusion effect and high time efficiency compared with similar scrambling algorithms. • The present study developed 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 image 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. • By using the DWSPF and the new strategy of plaintext association, a symmetric plaintext-related image cryptosystem is developed. An extensive experimental simulations and security analysis show that the proposed cryptosystem has excellent computational efficiency and can effectively resist various existing attacks, including powerful chosen plaintext attacks. [ABSTRACT FROM AUTHOR]

In this paper, a new 4D hyperchaotic nonlinear dynamical system with two positive Lyapunov exponents is presented. Exhaustive dynamic analyses of the novel hyperchaotic model using several dynamical studies are described. The dynamics of the system considered are first investigated analytically and numerically to explore phenomena and the selection of hyperchaotic behavior utilized for designing image cryptosystem. Since the proposed hyperchaotic model has rich dynamics, it displays hidden attractors. It emerges from this dynamic the existence of a single unstable equilibrium point giving rise to self-excited attractors, hysteresis phenomenon, and hyperchaotic behavior strongly recommended for securing information by its character. Furthermore, the feasibility and synchronization of the proposed system are also presented by developing, respectively, Raspberry surveys and an adaptive synchronization approach of two identical hyperchaotic systems. By employing the hyperchaotic behavior of the 4D map, an image encryption scheme is proposed as well. It is one round of a pixel-based permutation and a bit-wise diffusion phase. The secret key of the 4D map is derived from the SHA-256 value of the input image. It acts as the signature of the input image. Hence, the secret key exhibits high sensitivity to single-bit alteration in the image, which makes the cryptosystem robust against chosen/known-plaintext attacks. Performance analyses prove that the proposed cryptosystem provides the best in terms of the performance/complexity trade-off, as compared to some recently published algorithms. [ABSTRACT FROM AUTHOR]

To keep transmitted messages secret, straightforward encryption is an effective method. Taking efficiency into account, recently partial encryption has become widely accepted for images, audio and video. However, a new efficient approach is required in cases where a large number of images are intentionally transmitted to the same destination. An encryption algorithm for images based on vector quantization was proposed by Chang, Hwang and Chen, in which encrypting a common codebook is suggested to be the better choice of their two proposed schemes, because many images can be transmitted with only one encrypted corresponding codebook. However, in the present paper, the vulnerability of the CHC image cryptosystem is found according to the chosen-plainimage attack if the common codebook is used to encrypt a large number of images. And based on the cipherimage-only attack, keeping the index sets in a clear form is shown not to be a good idea. Accordingly, a way of securing the transmitted images is recommended. [ABSTRACT FROM AUTHOR]

Image dyadic displacements can be considered a unique pixel address permutation. This property can be exploited to obtain perfect decryption when encrypting an image. This work presents a hybrid image cryptosystem based on the holographic interference and dyadic permutations. First, the phase and amplitude of the Fourier transform of an input image are recorded as the intensity information via the holographic interference. The extracted phase is then processed via dyadic permutations by applying the exclusive-OR (XOR) operations to a user key and phase information addresses. Decryption uses an asymmetric process to recover the original image. Simulation results are provided to verify the proposed cryptosystem and demonstrate that it is robust to additional noise. [Copyright &y& Elsevier]

Image cryptosystems aim to secure the transmission of images in the presence of adversaries in the network. For ensuring confidentiality, images are encrypted to form unintelligible cipher images, the algorithms of which are much different from those for text data. Most image cryptosystems follow confusion–diffusion or complex architectures, which involves permutation and substitution of pixel values. Often these are done using chaotic maps and involve binary operations such as bitwise XOR, addition–subtraction, DNA operations, etc., each of which has certain limitations. Most of the cryptosystems for medical images proposed in the literature encrypt 8-bit compressed versions of the images rather than the standard 16-bit DICOM version, which results in loss of information. This paper presents a novel binary operation that can be used for all types of image cryptosystems — from DICOM medical to natural images using both conventional and DNA approaches. The use of this operation has been tested on a proposed DNA-based cryptosystem, which has novel steps for encryption to overcome the drawbacks of some existing ones. The cryptosystem has been tested on several images of varying pixel depth and dimensions, and the results obtained meet the standards of a secured image encryption system. • A novel binary operator forms an Abelian Group with a set of elements. • The operator can be used in both conventional and DNA based image cryptosystems. • The cryptosystem can efficiently encrypt images of 8-bit and 16-bit pixel depth. • Encryption is lossless, therefore it is very efficient for medical images. • The operator performs better than conventional XOR or addition–subtraction. [ABSTRACT FROM AUTHOR]

Biometric-based authentication systems are promising because of unique biometric features for each person. Generally, biometric features are generated , and biometric templates or bio-hash codes are calculated and stored in Authentication Data Table (ADT) along with userid. However, such hashing based authentication is vulnerable to precomputed table attacks. Also, in some cases, the service providers outsource the ADT to cloud or untrusted server. In this paper, a novel biometric-based authentication system is proposed using two servers: crypto-match server and untrusted storage server. The system utilizes biometric image cryptosystem, cryptographic hashing, and Paillier cryptosystem. In the proposed cryptosystem, keystreams are generated from Henon and logistic maps. The control parameters of these chaotic maps are calculated from the input biometric image. The proposed biometric encryption is able to resist statistical and differential attacks and its security level is also validated through various analyzes. Also, the attacks related to the privacy of ADT are analyzed. • Novel biometric image cryptosystem is developed. • Privacy-preserving biometric authentication is designed using proposed encryption. • Encryption key depends on input biometric to withstand differential attacks. • Because of improved speed and security, the proposed scheme can be used in real-time. • Security analysis is done through various factors. [ABSTRACT FROM AUTHOR]

Based on orthogonal Latin cubes, an image cryptosystem with confusion–diffusion–confusion cipher architecture has been proposed recently (Inf. Sci.2019, 478, 1–14). However, we find that there are four fatal vulnerabilities in this image cryptosystem, which leave open doors for cryptanalysis. In this paper, we propose a reference-validation inference algorithm and design screening-based rules to efficiently break the image cryptosystem. Compared with an existing cryptanalysis algorithm, the proposed method requires fewer pairs of chosen plain-cipher images, and behaves stably since different keys, positions of chosen bits and contents of plain images will not affect the cryptanalysis performance. Experimental results show that our cryptanalysis algorithm only requires   8 × H × W 3 + 3   pairs of chosen plain-cipher images, where H × W represents the image's resolution. Comparative studies demonstrate effectiveness and superiority of the proposed cryptanalysis algorithm. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]