A novel chaos-based bit-level permutation scheme for digital image encryption

Confidentiality is an important issue when digital images are transmitted over public networks, and encryption is the most useful technique employed for this purpose. Image encryption is somehow different from text encryption due to some inherent features of image such as bulk data capacity and high correlation among pixels, which are generally difficult to handle by conventional algorithms. Recently, chaos-based encryption has suggested a new and efficient way to deal with the intractable problems of fast and highly secure image encryption. This paper proposes a novel chaos-based bit-level permutation scheme for secure and efficient image cipher. To overcome the drawbacks of conventional permutation-only type image cipher, the proposed scheme introduced a significant diffusion effect in permutation procedure through a two-stage bit-level shuffling algorithm. The two-stage permutation operations are realized by chaotic sequence sorting algorithm and Arnold Cat map, respectively. Results of various types of analysis are interesting and indicate that the security level of the new scheme is competitive with that of permutation-diffusion type image cipher, while the computational complexity is much lower. Therefore the new scheme is a good candidate for real-time secure image communication applications.     

A novel chaos-based image encryption scheme with an efficient permutation-diffusion mechanism

This paper proposes a novel chaos-based image encryption scheme with an efficient permutation-diffusion mechanism, in which permuting the positions of image pixels incorporates with changing the gray values of image pixels to confuse the relationship between cipher-image and plain-image. In the permutation process, a generalized Arnold map is utilized to generate one chaotic orbit used to get two index order sequences for the permutation of image pixel positions; in the diffusion process, a generalized Arnold map and a generalized Bernoulli shift map are employed to yield two pseudo-random gray value sequences for a two-way diffusion of gray values. The yielded gray value sequences are not only sensitive to the control parameters and initial conditions of the considered chaotic maps, but also strongly depend on the plain-image processed, therefore the proposed scheme can resist statistical attack, differential attack, known-plaintext as well as chosen-plaintext attack. Experimental results are carried out with detailed analysis to demonstrate that the proposed image encryption scheme possesses large key space to resist brute-force attack as well.     

An image encryption scheme using generalized Arnold map and affine cipher

This paper aims to provide an image encryption scheme with an efficient bit-level permutation and a pixel-level diffusion procedure. In the bit-level permutation, we divide each pixel into 8 bits, and arrange the positions of each bit by the generalized Arnold map in row and column direction. Hence, a significant diffusion effect is happened in the bit-level permutation. In the pixel-level diffusion procedure, we apply affine cipher to change the gray value and the histogram distribution of the permutated image. Various types of security analyses demonstrate that the proposed scheme is competitive with that ordinary permutation–diffusion type image cipher and proper for practical image encryption.     

Double-image encryption by using chaos-based local pixel scrambling technique and gyrator transform

A novel double-image encryption algorithm is proposed by using chaos-based local pixel scrambling technique and gyrator transform. Two original images are first regarded as the amplitude and phase of a complex function. Arnold transform is used to scramble pixels at a local area of the complex function, where the position of the scrambled area and the Arnold transform frequency are generated by the standard map and logistic map respectively. Then the changed complex function is converted by gyrator transform. The two operations mentioned will be implemented iteratively. The system parameters in local pixel scrambling and gyrator transform serve as the keys of this encryption algorithm. Numerical simulation has been performed to test the validity and the security of the proposed encryption algorithm.     

A fast image encryption method by using chaotic 3D cat maps

An image encryption method using a chaotic 3D cat map is presented in this paper. The process of the proposed algorithm contains the simultaneous operations of pixels’ locations permutation and pixels’ values substitution at every iterative step of the chaotic map, which making the forward and reverse encryption needs only one traverse of the image pixels. Moreover, a perturbation is introduced to eliminate the undesirable finite precision effect of computer in realization. The main advantages of such a secure method are the simplicity and efficiency. Both simulations and analysis show the proposed algorithm can produce a large key space and resist the common existing cipher attacks. These good cryptographic properties make it suitable for image applications.     

A novel chaos-based image encryption algorithm using DNA sequence operations

An image encryption algorithm based on chaotic system and deoxyribonucleic acid (DNA) sequence operations is proposed in this paper. First, the plain image is encoded into a DNA matrix, and then a new wave-based permutation scheme is performed on it. The chaotic sequences produced by 2D Logistic chaotic map are employed for row circular permutation (RCP) and column circular permutation (CCP). Initial values and parameters of the chaotic system are calculated by the SHA 256 hash of the plain image and the given values. Then, a row-by-row image diffusion method at DNA level is applied. A key matrix generated from the chaotic map is used to fuse the confused DNA matrix; also the initial values and system parameters of the chaotic system are renewed by the hamming distance of the plain image. Finally, after decoding the diffused DNA matrix, we obtain the cipher image. The DNA encoding/decoding rules of the plain image and the key matrix are determined by the plain image. Experimental results and security analyses both confirm that the proposed algorithm has not only an excellent encryption result but also resists various typical attacks.     

Cryptanalysis of a spatiotemporal chaotic image/video cryptosystem and its improved version

Recently, a spatiotemporal chaotic image/video cryptosystem was proposed by Lian. Shortly after its publication, Rhouma et al. proposed two attacks on the cryptosystem. They as well introduced an improved cryptosystem which is more secured under attacks (R. Rhouma, S. Belghith, Phys. Lett. A 372 (2008) 5790) [29]. This Letter re-examines securities of Lian's cryptosystem and its improved version, by showing that not all details of the ciphered image of Lian's cryptosystem can be recovered by Rhouma et al.'s attacks due to the incorrectly recovered part of the sign-bits of the AC coefficients with an inappropriately chosen image. As a result, modifications of Rhouma et al.'s attacks are proposed in order to recover the ciphered image of Lian's cryptosystem completely; then based on the modifications, two new attacks are proposed to break the improved version of Lian's cryptosystem. Finally, experimental results illustrate the validity of our analysis.     

A novel chaotic image encryption algorithm using block scrambling and dynamic index based diffusion

In this paper, we propose a novel chaotic image encryption algorithm which involves a block image scrambling scheme and a new dynamic index based diffusion scheme. Firstly, the original image is divided into two equal blocks by vertical or horizontal directions. Then, we use the chaos matrix to construct X coordinate, Y coordinate and swapping control tables. By searching the X coordinate and Y coordinate tables, the swapping position of the processing pixel is located. The swapping control table is used to control the swapping of the pixel in the current block or the other block. Finally, the dynamic index scheme is applied to the diffusing of the scrambled image. The simulation results and performance analysis show that the proposed algorithm has an excellent safety performance with only one round.     

A novel image encryption method based on total shuffling scheme

In this paper, a novel image encryption method based on skew tent chaotic map and permutation-diffusion architecture is proposed. In the proposed method, the P-box is chosen as the same size of plain-image, which shuffles the positions of pixels totally. The keystream generated by skew tent chaotic map is related to the plain-image. Statistical analysis, information entropy analysis, and sensitivity analysis to plaintext and key on the proposed scheme are provided in this paper. It can be seen that this algorithm is efficient and reliable, with high potential to be adopted for network security and secure communications.     

A robust and secure chaotic standard map based pseudorandom permutation-substitution scheme for image encryption

A novel and robust chaos-based pseudorandom permutation-substitution scheme for image encryption is proposed. It is a loss-less symmetric block cipher and specifically designed for the color images but may also be used for the gray scale images. A secret key of 161-bit, comprising of the initial conditions and system parameter of the chaotic map (the standard map), number of iterations and number of rounds, is used in the algorithm. The whole encryption process is the sequential execution of a preliminary permutation and a fix number of rounds (as specified in the secret key) of substitution and main permutation of the 2D matrix obtained from the 3D image matrix. To increase the speed of encryption all three processes: preliminary permutation, substitution and main permutation are done row-by-row and column-by-column instead of pixel-by-pixel. All the permutation processes are made dependent on the input image matrix and controlled through the pseudo random number sequences (PRNS) generated from the discretization of chaotic standard map which result in both key sensitivity and plaintext sensitivity. However each substitution process is initiated with the initial vectors (different for rows and columns) generated using the secret key and chaotic standard map and then the properties of rows and column pixels of input matrix are mixed with the PRNS generated from the standard map. The security and performance analysis of the proposed image encryption has been performed using the histograms, correlation coefficients, information entropy, key sensitivity analysis, differential analysis, key space analysis, encryption/decryption rate analysis etc. Results suggest that the proposed image encryption technique is robust and secure and can be used for the secure image and video communication applications.     

A novel chaotic image encryption scheme using DNA sequence operations

In this paper, we propose a novel image encryption scheme based on DNA (Deoxyribonucleic acid) sequence operations and chaotic system. Firstly, we perform bitwise exclusive OR operation on the pixels of the plain image using the pseudorandom sequences produced by the spatiotemporal chaos system, i.e., CML (coupled map lattice). Secondly, a DNA matrix is obtained by encoding the confused image using a kind of DNA encoding rule. Then we generate the new initial conditions of the CML according to this DNA matrix and the previous initial conditions, which can make the encryption result closely depend on every pixel of the plain image. Thirdly, the rows and columns of the DNA matrix are permuted. Then, the permuted DNA matrix is confused once again. At last, after decoding the confused DNA matrix using a kind of DNA decoding rule, we obtain the ciphered image. Experimental results and theoretical analysis show that the scheme is able to resist various attacks, so it has extraordinarily high security.     

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.     

Color image encryption using skew tent map and hyper chaotic system of 6th-order CNN

The paper designs a color image encryption scheme based on skew tent map and hyper chaotic system of 6th-order CNN. The essence of the image encryption is to confuse and diffuse the pixels, the skew tent map is applied to generate the confusion sequence, and the hyper chaotic system of 6th-order CNN is applied to generate the diffusion sequence, for 6 state variables in the system, there are total 120 combinations. For each pixel of the plain image, one combination is chosen to encryption the red, green and blue components, and the combination is determined by one of the state variables. Each pixel is encrypted by the cipher value of the previous pixel and the combination value of the CNN system. Experimental results and security analysis demonstrate that the scheme can achieve good encryption result and larger key space, and can resist common attacks, so the scheme can be applied in secure communication to enhance the security of transmitting image.     

An image encryption scheme based on new spatiotemporal chaos

Spatiotemporal chaos is chaotic dynamics in spatially extended system, which has attracted much attention in the image encryption field. The spatiotemporal chaos is often created by local nonlinearity dynamics and spatial diffusion, and modeled by coupled map lattices (CML). This paper introduces a new spatiotemporal chaotic system by defining the local nonlinear map in the CML with the nonlinear chaotic algorithm (NCA) chaotic map, and proposes an image encryption scheme with the permutation-diffusion mechanism based on these chaotic maps. The encryption algorithm diffuses the plain image with the bitwise XOR operation between itself pixels, and uses the chaotic sequence generated by the NCA map to permute the pixels of the resulting image. Finally, the constructed spatiotemporal chaotic sequence is employed to diffuse the shuffled image. The experiments demonstrate that the proposed encryption scheme is of high key sensitivity and large key space. In addition, the scheme is secure enough to resist the brute-force attack, entropy attack, differential attack, chosen-plaintext attack, known-plaintext attack and statistical attack.     

A lightweight symmetric image encryption cryptosystem in wavelet domain based on an improved sine map

In the era of big data, the number of images transmitted over the public channel increases exponentially. As a result,it is crucial to devise the efficient and highly secure encryption method to safeguard the sensitive image. In this paper, an improved sine map(ISM) possessing a larger chaotic region, more complex chaotic behavior and greater unpredictability is proposed and extensively tested. Drawing upon the strengths of ISM, we introduce a lightweight symmetric image encryption cryptosystem ...     

Cryptanalysis on a novel image encryption method based on total shuffling scheme

A novel image encryption method based on a skew tent map is proposed recently. In this paper, some flaws of this algorithm are pointed out and then a chosen plaintext attack against it is presented. Both theoretical analysis and experimental simulation indicate that the plain image can be recovered exactly from the cipher image without the secret key. So it can be seen that this algorithm is not secure enough to be applied in network communication.     

A novel image block cryptosystem based ona spatiotemporal chaotic system and a chaotic neural network

In this paper, we propose a novel block cryptographic scheme based on a spatiotemporal chaotic system and a chaotic neural network (CNN). The employed CNN comprises a 4-neuron layer called a chaotic neuron layer (CNL), where the spatiotemporal chaotic system participates in generating its weight matrix and other parameters. The spatiotemporal chaotic system used in our scheme is the typical coupled map lattice (CML), which can be easily implemented in parallel by hardware. A 160-bit-long binary sequence is used to generate the initial conditions of the CML. The decryption process is symmetric relative to the encryption process. Theoretical analysis and experimental results prove that the block cryptosystem is secure and practical, and suitable for image encryption.     

A novel color image encryption scheme using alternate chaotic mapping structure

This paper proposes an color image encryption algorithm using alternate chaotic mapping structure. Initially, we use the R, G and B components to form a matrix. Then one-dimension logistic and two-dimension logistic mapping is used to generate a chaotic matrix, then iterate two chaotic mappings alternately to permute the matrix. For every iteration, XOR operation is adopted to encrypt plain-image matrix, then make further transformation to diffuse the matrix. At last, the encrypted color image is obtained from the confused matrix. Theoretical analysis and experimental results has proved the cryptosystem is secure and practical, and it is suitable for encrypting color images.     

A new feedback image encryption scheme based on perturbation with dynamical compound chaotic sequence cipher generator

The design of the new compound two-dimensional chaotic function is presented by exploiting two one-dimensional chaotic functions which switch randomly, and the design is used as a chaotic sequence generator which is proved by Devaney’s definition proof of chaos. The properties of compound chaotic functions are also proved rigorously. In order to improve the robustness against difference cryptanalysis and produce avalanche effect, a new feedback image encryption scheme is proposed using the new compound chaos by selecting one of the two one-dimensional chaotic functions randomly and a new image pixels method of permutation and substitution is designed in detail by array row and column random controlling based on the compound chaos. The results from entropy analysis, difference analysis, statistical analysis, sequence randomness analysis, cipher sensitivity analysis depending on key and plaintext have proven that the compound chaotic sequence cipher can resist cryptanalytic, statistical and brute-force attacks, and especially it accelerates encryption speed, and achieves higher level of security. By the dynamical compound chaos and perturbation technology, the paper solves the problem of computer low precision of one-dimensional chaotic function.     

A fast image encryption algorithm based on only blocks in cipher text

In this paper, a fast image encryption algorithm is proposed, in which the shuffling and diffusion is performed simul- taneously. The cipher-text image is divided into blocks and each block has k x k pixels, while the pixels of the plain-text are scanned one by one. Four logistic maps are used to generate the encryption key stream and the new place in the cipher image of plain image pixels, including the row and column of the block which the pixel belongs to and the place where the pixel would be placed in the block. After encrypting each pixel, the initial conditions of logistic maps would be changed ac- cording to the encrypted pixel＇s value; after encrypting each row of plain image, the initial condition would also be changed by the skew tent map. At last, it is illustrated that this algorithm has a faster speed, big key space, and better properties in withstanding differential attacks, statistical analysis, known plaintext, and chosen plaintext attacks.