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.     

一种超混沌图像加密算法的安全性分析及其改进

根据Kerckhoff准则, 从选择明文攻击和选择密文攻击出发, 对一种超混沌图像加密算法进行分析,结果表明该算法密钥流与明文无关,并且一个明文字节只能影响一个密文字节,导致利用选择明文攻击和选择密文攻击能够以很小的计算代价破译密文.基于此,本文提出一种改进的超混沌图像加密算法,并进行了统计分析、差分分析、相关性分析及密钥敏感性测试.理论分析及仿真结果表明,改进算法不仅可以抵御选择明文攻击和选择密文攻击,而且具有较好的统计特性及差分特性等密码学特性. 关键词： 超混沌 选择明文攻击 选择密文攻击 Matlab分析     

对一类超混沌图像加密算法的密码分析与改进

对一种超混沌图像加密算法及其改进版进行了安全性分析, 结果表明该类算法的置乱过程都是与混淆过程相脱离的, 且混淆过程的加密公式简单; 因此都不能抵抗选择明文和选择密文攻击. 进而提出了一种改进的加强型超混沌图像加密算法; 改进算法包含两轮像素值替代加密操作, 并使得密文与明文、密钥之间的关系更复杂. 安全性分析和实验测试表明, 改进算法不仅克服了原算法不能抵御选择明文和选择密文攻击的缺陷; 而且具有时间开销更小和抗差分攻击性能更好的优势.     

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.     

一种多混沌系统公钥密码算法的安全性分析

最近，Ranjan利用m组混沌系统及线性变换组合方法提出一种混沌公钥密码.安全分析表明攻击该公钥密码难度为(NP)^m，其中N，P分别为密钥空间大小及线性变换复杂度.由于向量任意的线性变换都能映射为向量2-范数简单的幅度变化，据此提出一种仅依赖公钥、初始向量及算法结构的私钥攻击算法.分析与实验结果均表明该多混沌公钥密码无法抵抗此类攻击，并且该分析方法可以有效攻击各种多混沌公钥密码算法. 关键词： 公钥密码 多混沌系统 密码分析     

基于Hadoop大数据平台和无简并高维离散超混沌系统的加密算法

针对目前大数据环境中存在的数据安全问题,提出一种基于Hadoop大数据平台和无简并高维离散超混沌系统的加密算法.算法采用流密码对称加密方式,在Hadoop平台上读取存储于HDFS(Hadoop distributed file system)的大数据,进行分片处理和MapReduce编程后,用Map函数实现数据并行加密和解密,通过Reduce函数实现数据的合并操作并存储于HDFS.该算法具有较好的执行效率.与正李氏指数发生简并的低维混沌系统相比,无简并高维离散超混沌加密算法能提高系统安全性能,李氏指数均为正并且足够大,具有更好的统计特性,可通过严格的TESTU01测试,并行加密的密文之间互相关性很小.密钥参数众多使得估计或辨识难度增大.在密文闭环反馈条件下,具有抵御已知明文攻击和选择明文攻击的能力.     

一种基于遍历性的混沌加密新算法

分析了E.Álvarez密码系统的加密方法及其弱点,在此基础上给出了一种基于遍历性的混沌加密新算法。即以混沌系统的控制参数和初始点为密钥,迭代混沌映射以便产生一个比特链,在该比特链中搜索明文分组,记下迭代次数作为密文分组。新算法避免了E.Álvarez密码方案中的若干弱点,增强了密码系统的安全性。最后通过对Logistic映射的仿真研究,验证了新密码系统满足密码学中的混淆和散布特性,并进而阐明了新密码系统的有效性。     

一类时空混沌加解密系统的安全分析

本文安全分析文献 所提的一类自同步的时空混沌流密码系统.发现该高维的加解密系统在常数的驱动下将收敛到一维,使得动力学系统的复杂性大为降低.在某些特定输入区域内容,保密系统对输入状态的微小扰动不敏感.可以建立密钥和特殊输入状态间一个简单的线性关系,并依次从密钥流中恢复出密钥.基于此,提出一套选择密文攻击方法,利用系统参数和扰动前后密钥流的差异之间的依赖关系通过寻优算法破解密钥,从而攻击了上述文献所提出的基于混沌自同步的安全通信算法. 关键词： 混沌密码 耦合映像格子 安全分析     

双随机相位加密系统的已知明文攻击

运用密码分析学的方法对双随机相位加密系统进行了初步的安全性分析.研究结果表明，该系统属于线性的对称分组密码系统，线性性质为其安全性留下隐患.在已知明文攻击下，攻击者可通过常规的相位恢复算法获得4-f系统输入平面的随机相位函数密钥，继而可轻易推出频谱平面的随机相位函数密钥，从而攻破此密码系统. 关键词： 光学信息安全 双随机相位加密 密码分析学 已知明文攻击     

基于混沌神经网络的单向Hash函数

提出了一种基于混沌神经网络的单向Hash函数，该方法通过使用以混沌分段线性函数作为输出函数的神经网络和基于时空混沌的密钥生成函数实现明文和密钥信息的混淆和扩散，并基于密码块连接模式实现对任意长度的明文序列产生128位的Hash值.理论分析和实验结果表明，提出的Hash函数可满足所要求的单向性，初值和密钥敏感性，抗碰撞性和实时性等要求. 关键词： 混沌神经网络 Hash函数 分段线性混沌映射 时空混沌     

A novel image encryption scheme based on improved hyperchaotic sequences

This paper proposes a novel image encryption scheme based on the improved hyperchaotic sequences. Firstly, the hyperchaotic sequences are modified to generate chaotic key stream that is more suitable for image encryption. Secondly, the final encryption key stream is generated by correlating the chaotic key stream and plaintext which result in both key sensitivity and plaintext sensitivity. The scheme can achieve high key sensitivity and high plaintext sensitivity through only two rounds diffusion operation. The performance test and security analysis has been performed using the histograms, correlation coefficients, information entropy, peak signal-to-noise ratio, key sensitivity analysis, differential analysis, key space analysis, decryption quality and speed analysis. Results suggest that the proposed image encryption scheme is secure and reliable, with high potential to be adopted for the secure image communication applications.     

A one-time one-key encryption algorithm based on the ergodicity of chaos

In this paper, we propose a new one-time one-key encryption algorithm based on the ergodicity of a skew tent chaotic map. We divide the chaotic trajectory into sub-intervals and map them to integers, and use this scheme to encrypt plaintext and obtain ciphertext. In this algorithm, the plaintext information in the key is used, so different plaintexts or different total numbers of plaintext letters will encrypt different ciphertexts. Simulation results show that the performance and the security of the proposed encryption algorithm can encrypt plaintext effectively and resist various typical attacks.     

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 image encryption scheme based on the MLNCML system using DNA sequences

We propose a new image scheme based on the spatiotemporal chaos of the Mixed Linear–Nonlinear Coupled Map Lattices (MLNCML). This spatiotemporal chaotic system has more cryptographic features in dynamics than the system of Coupled Map Lattices (CML). In the proposed scheme, we employ the strategy of DNA computing and one time pad encryption policy, which can enhance the sensitivity to the plaintext and resist differential attack, brute-force attack, statistical attack and plaintext attack. Simulation results and theoretical analysis indicate that the proposed scheme has superior high security.     

High-performance multimedia encryption system based on chaos

Current chaotic encryption systems in the literature do not fulfill security and performance demands for real-time multimedia communications. To satisfy these demands, we propose a generalized symmetric cryptosystem based on N independently iterated chaotic maps (N-map array) periodically perturbed with a three-level perturbation scheme and a double feedback (global and local) to increase the system's robustness to attacks. The first- and second-level perturbations make cryptosystem extremely sensitive to changes in the plaintext data since the system's output itself (ciphertext global feedback) is used in the perturbation process. Third-level perturbation is a system reset, in which the system-key and chaotic maps are replaced for totally new values. An analysis of the proposed scheme regarding its vulnerability to attacks, statistical properties, and implementation performance is presented. To the best of our knowledge we provide a secure cryptosystem with one of the highest levels of performance for real-time multimedia communications.     

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.     

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.     

Embedding adaptive arithmetic coder in chaos-based cryptography

In this study an adaptive arithmetic coder is embedded in the Baptista-type chaotic cryptosystem for implementing secure data compression. To build the multiple lookup tables of secure data compression, the phase space of chaos map with a uniform distribution in the search mode is divided non-uniformly according to the dynamic probability estimation of plaintext symbols. As a result, more probable symbols are selected according to the local statistical characters of plaintext and the required number of iterations is small since the more probable symbols have a higher chance to be visited by the chaotic search trajectory. By exploiting non-uniformity in the probabilities under which a number of iteration to be coded takes on its possible values, the compression capability is achieved by adaptive arithmetic code. Therefore, the system offers both compression and security. Compared with original arithmetic coding, simulation results on Calgary Corpus files show that the proposed scheme suffers from a reduction in compression performance less than 12{\%} and is not susceptible to previously carried out attacks on arithmetic coding algorithms.