Cryptanalysis on an image block encryption algorithm based on spatiotemporal chaos

An image block encryption scheme based on spatiotemporal chaos has been proposed recently.In this paper,we analyse the security weakness of the proposal.The main problem of the original scheme is that the generated keystream remains unchanged for encrypting every image.Based on the flaws,we demonstrate a chosen plaintext attack for revealing the equivalent keys with only 6 pairs of plaintext/ciphertext used.Finally,experimental results show the validity of our attack.     

Comments on “Color image encryption using Choquet fuzzy integral and hyper chaotic system”

An image encryption system whose cipher code stream only controlled by the secret key, but has nothing to do with the plaintext, is vulnerable to chosen plaintext attacks. Recently, an image encryption scheme using Choquet fuzzy integral and hyper chaotic Lorenz system has been proposed Liu et al. (2013), which employed plaintext-independent cipher code stream, then should be subjected to chosen plaintext attack. This paper cryptanalyzed the aforesaid encryption scheme using chosen plaintext attack, and pointed out that even if possessing good pseudorandom cipher code generation method, the encryption system is still insecure with unreasonable designed encryption scheme.     

Cryptanalysis and improvement of a digital image encryption method with chaotic map lattices

A digital image encryption scheme using chaotic map lattices has been proposed recently. In this paper, two fatal flaws of the cryptosystem are pointed out. According to these two drawbacks, cryptanalysts could recover the plaintext by applying the chosen plaintext attack. Therefore, the proposed cryptosystem is not secure enough to be used in the image transmission system. Experimental results show the feasibility of the attack. As a result, we make some improvements to the encryption scheme, which can completely resist our chosen plaintext attack.     

Novel image encryption algorithm based on cycle shift and chaotic system

In this paper, a novel image encryption algorithm is proposed. The cycle shift in bits of pixels and the chaotic system are employed for the encryption of the proposed scheme. For cycle shift operations, random integers with the same size of the original image are produced to scramble the plaintext image. Moreover, the scrambled image effects the initial values of the chaotic system for the further encryption process, which increases the sensitivity of plaintext images of the scheme. The scrambled image is encrypted into the ciphered image by the keys which are produced by the chaotic system. The simulation experiments and theoretical analyses indicate that the proposed scheme is superior and able to resist exhaustive attack and statistical attack.     

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.     

Coupled map lattices as spatio-temporal fitness functions: Landscape measures and evolutionary optimization

Coupled Map Lattices (CML) can be interpreted as spatio-temporal fitness landscapes which may pose a dynamic optimization problem. In this paper, we analyze such dynamic fitness landscapes in terms of the landscape measures modality, ruggedness, information content and epistasis. These measures account for different aspects of problem hardness. We use an evolutionary algorithm to solve the dynamic optimization problem and study the relationship between performance criteria of the algorithm and the landscape measures. In this way we relate problem hardness to expectable performance.     

On the security of a class of discrete-time chaotic cryptosystems

In this Letter we analyze the security of some recently proposed chaotic cryptosystems and give methods to break the cipher to reveal the encrypted information. The method exploits the dependencies between the parameters and the output sequence of a dynamical system to reveal the secretly shared system parameters. For each encryption scheme a known plaintext attack and a ciphertext only attack are given.     

An improved method to enhance the security of double random-phase encoding in the Fresnel domain

Optical encryption technique based on double random-phase encoding in the Fresnel domain (named as FrDRPE) has been shown to be vulnerable to the chosen-plaintext attack owing to the linear property of the Fresnel transform. To negate such an attack, different phase-masks (i.e. part of the encryption keys of FrDRPE) are used in our system to encrypt different plaintexts while the number of the transmitted keys is not increased. In this case, a plurality of plaintext–ciphertext pairs corresponding to the same encryption key that are needed in the chosen-plaintext attack cannot be acquired by our improved system. Accordingly, this system can successfully resist the chosen-plaintext attack. Some numerical simulations are performed to validate the feasibility of our proposed scheme.     

A bit-level image encryption algorithm based on spatiotemporal chaotic system and self-adaptive

This paper proposes a bit-level image encryption algorithm based on spatiotemporal chaotic system which is self-adaptive. We use a bit-level encryption scheme to reduce the volume of data during encryption and decryption in order to reduce the execution time. We also use the adaptive encryption scheme to make the ciphered image dependent on the plain image to improve performance. Simulation results show that the performance and security of the proposed encryption algorithm can encrypt plaintext effectively and resist various typical attacks.     

Modified Baptista type chaotic cryptosystem via matrix secret key

In 1998, M.S. Baptista proposed a chaotic cryptosystem using the ergodicity property of the simple low-dimensional and chaotic logistic equation. Since then, many cryptosystems based on Baptista's work have been proposed. However, over the years research has shown that this cryptosystem is predictable and vulnerable to attacks and is widely discussed. Among the weaknesses are the non-uniform distribution of ciphertexts and succumbing to the one-time pad attack (a type of chosen plaintext attack). In this Letter, our objective is to modify the chaotic cryptographic scheme proposed previously. We use a matrix secret key such that the cryptosystem would no longer succumb to the one-time pad attack.     

Analysis and design of impulse attack free generalized joint transform correlator optical encryption scheme

We demonstrate in this paper that the generalized joint transform correlator (JTC) optical encryption method shows vulnerability to chosen-plaintext attacks. An unauthorized user, who has access to probe the encryption machine, can obtain the encryption keys with the help of the impulse function as chosen plaintext. The vulnerability of traditional joint transform correlator encryption is also analyzed in this paper. To prevent this attack, an enhanced angular multiplexing double-arm encryption solution is proposed. Cryptanalysis indicates that the improved scheme is robust to the chosen-plaintext attacks. Based on the analysis, a guideline for designing impulse attack free encryption system is discussed. Numerical simulation is also presented to show the validity of the proposed approach.     

使用参考光波光学联合变换相关加密系统的选择明文攻击

证实了一种使用参考光波的光学联合相关变换加密系统对于选择明文攻击的脆弱性。在该加密系统中,通过选择一个透过率为零的特殊明文图像,记录其对应的联合功率谱,之后再通过遮挡输入面获取参考光波强度、遮挡参考光和明文获得加密密钥的傅里叶变换强度,根据获得的3幅图像,攻击者可以准确地获取加密所用的密钥,进而可以恢复出原始图像。理论分析和计算机模拟结果均证明所提攻击方法的有效性。     

一类改进的混沌迭代加密算法

指出了最近提出的一类混沌迭代分组密码算法的缺陷,通过选择明文攻击可以恢复出置换后的明文.算法中二进制序列的产生只依赖于密钥,而与明文无关,从而使算法容易造成信息泄露并遭受攻击.基于此,给出了一种可以抵御选择明文攻击的安全性更高的算法. 关键词： 混沌 混沌密码 攻击 安全性     

一种基于时滞混沌的加密算法

基于半导体激光时滞混沌映射,提出一种新的加密算法.用Ikeda方程产生的二进制序列掩盖明文,对明文块做依赖于密钥的置换,并用传统的混沌加密方法加密.在每一轮加密过程中,都会用一个与混沌映射、明文和密文相关的随机数对时滞项做微扰,以提高算法的安全性;状态转移函数不仅与密钥相关,而且与本轮输入的明文符号以及上一轮输出的密文符号相关,有效地防止了选择明文/密文攻击.仿真实验表明,该算法可行、有效.     

Security enhancement of double-random phase encryption by amplitude modulation

Conventional double-random phase encoding is vulnerable to a chosen or known plaintext attack owing to the linearity of the system. We introduce a technique to break down this linearity with an undercover amplitude modulation in the encryption scheme. As an additional key, this operation can significantly enhance the security of the system. A series of computer simulations have shown the effectiveness of this method and its resistance against the known plaintext attack. The design and parameter choice of the amplitude modulator is also discussed.     

On the security of a spatiotemporal chaotic cryptosystem

Recently, Tang et al. [Phys Lett. A 318, 388 (2003)] proposed a spatiotemporal cryptosystem based on one-way coupled map lattices. They claim that it has high security, fast encryption speed, and short synchronization transient. This work proves that this scheme has some security weaknesses. Indeed, we propose an attack which the system cannot withstand.     

A self-cited pixel summation based image encryption algorithm

In this paper, a novel image encryption algorithm is presented based on self-cited pixel summation. With the classical mechanism of permutation plus diffusion, a pixel summation of the plain image is employed to make a gravity influence on the pixel positions in the permutation stage. Then, for each pixel in every step of the diffusion stage, the pixel summation calculated from the permuted image is updated. The values from a chaotic sequence generated by an intertwining logistic map are selected by this summation. Consequently, the keystreams generated in both stages are dependent on both the plain image and the permuted image. Because of the sensitivity of the chaotic map to its initial conditions and the plain-image-dependent keystreams, any tiny change in the secret key or the plain image would lead to a significantly different cipher image. As a result, the proposed encryption algorithm is immune to the known plaintext attack (KPA) and the chosen plaintext attack (CPA). Moreover, experimental simulations and security analyses show that the proposed permutation-diffusion encryption scheme can achieve a satisfactory level of security.     

Cryptanalysis of a color image encryption algorithm based on chaos

A novel image encryption algorithm based on logistic map is proposed recently. In this paper, a chosen plaintext attack on this algorithm is presented and some other flaws of the algorithm are pointed out. Theoretical analysis and experimental simulation indicate that the plain image can be recovered exactly from the cipher image without secret key. Therefore, this algorithm is not secure enough for practical applications. An improvement is proposed to enhance the security of the original algorithm. Simulation results and theoretical analysis show that the improved scheme has expected cryptographic properties and is more secure than the original algorithm.     

An enhanced sub-image encryption method

Recently a parallel sub-image encryption method is proposed by Mirzaei et al., which is based on a total shuffling and parallel encryption algorithm. In this paper, we firstly show that the method can be attacked by chosen plaintext attack and then propose an enhanced sub-image algorithm, which can completely resist the chosen plaintext attack. Moreover, our improved algorithm can reduce the encryption time dramatically. The experimental results also prove that the improved encryption algorithm is secure enough. So the improved method can be used in image transmission system.     

Asymmetric multiple-image encryption based on coupled logistic maps in fractional Fourier transform domain

A multiple-image encryption scheme is proposed based on the asymmetric technique, in which the encryption keys are not identical to the decryption ones. First, each plain image is scrambled based on a sequence of chaotic pairs generated with a system of two symmetrically coupled identical logistic maps. Then, the phase-only function of each scrambled image is retrieved with an iterative phase retrieval process in the fractional Fourier transform domain. Second, all phase-only functions are modulated into an interim, which is encrypted into the ciphertext with stationary white noise distribution by using the fractional Fourier transform and chaotic diffusion. In the encryption process, three random phase functions are used as encryption keys to retrieve the phase-only functions of plain images. Simultaneously, three decryption keys are generated in the encryption process, which make the proposed encryption scheme has high security against various attacks, such as chosen plaintext attack. The peak signal-to-noise is used to evaluate the quality of the decrypted image, which shows that the encryption capacity of the proposed scheme is enhanced considerably. Numerical simulations demonstrate the validity and efficiency of the proposed method.