Cryptanalysis of a chaos-based cryptosystem with an embedded adaptive arithmetic coder

In this paper, we analyse a new chaos-based cryptosystem with an embedded adaptive arithmetic coder, which was proposed by Li Heng-Jian and Zhang J S （Li H J and Zhang J S 2010 Chin. Phys. B 19 050508）. Although this new method has a better compression performance than its original version, it is found that there are some problems with its security and decryption processes. In this paper, it is shown how to obtain a great deal of plain text from the cipher text without prior knowledge of the secret key. After discussing the security and decryption problems of the Li Heng-Jian et al. algorithm, we propose an improved chaos-based cryptosystem with an embedded adaptive arithmetic coder that is more secure.

An Improved S-Random Interleaver Design for Turbo Code Based on Chaos Model

A new method to design interleaver based on Henon chaos model is presented. The designed interleaver is with rather random behavior. Experimental results show that the proposed S-henon interleaver make a magnitude of im provement in bit error rate （BER） performance by 0.4 dB compared with the S-random interleaver for AWGN channel respectively. The S-henon interleaver may be adapted to 3G mobile communication systems.

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.

Application of the Henon Chaotic Model on to the Design of Low Density Parity Check Codes

A new method to design parity-check matrix based on Henon chaos model is presented. The designed parity-check matrix is with rather random behavior. Simulation results show that the proposed method makes an improvement in bit error rate （BER） performance by 0.4 dB compared with that of Luby for AWGN channel. The proposed method decreases the complexity of decoding significantly, and improves the error correcting performance of LDPC codes. It has been shown that Henon chaotic model is a powerful tool for construction of good LDPC codes, which make it possible to apply the LDPC code in real communication systems.

Performances of Chaos Coded Modulation Schemes Based on Mod-MAP Mapping and High Dimensional LDPC Based Mod-MAP Mapping with Belief Propagation

In this paper, we propose to generalize the coding schemes first proposed by Kozic &al to high spectral efficient modulation schemes. We study at first Chaos Coded Modulation based on the use of small dimensional modulo-MAP encoding process and we give a solution to study the distance spectrum of such coding schemes to accurately predict their performances. However, the obtained performances are quite poor. To improve them, we use then a high dimensional modulo-MAP mapping process similar to the low-density generator-matrix codes (LDGM) introduced by Kozic &al. The main difference with their work is that we use an encoding and decoding process on GF (2m) which enables to obtain better performances while preserving a quite simple decoding algorithm when we use the Extended Min-Sum (EMS) algorithm of Declercq &Fossorier.

Chaos-based encryption for fractal image coding

A chaos-based cryptosystem for fractal image coding is proposed. The Renyi chaotic map is employed to determine the order of processing the range blocks and to generate the keystream for masking the encoded sequence. Compared with the standard approach of fraetal image coding followed by the Advanced Encryption Standard, our scheme offers a higher sensitivity to both plaintext and ciphertext at a comparable operating efficiency. The keystream generated by the Renyi chaotic map passes the randomness tests set by the United States National Institute of Standards and Technology, and so the proposed scheme is sensitive to the key.

SR-DCSK Cooperative Communication System with Code Index Modulation:A New Design for 6G New Radios

This paper proposes a high-throughput short reference differential chaos shift keying cooperative communication system with the aid of code index modulation,referred to as CIM-SR-DCSK-CC system.In the proposed CIM-SR-DCSK-CC system,the source transmits information bits to both the relay and destination in the first time slot,while the relay not only forwards the source information bits but also sends new information bits to the destination in the second time slot.To be specific,the relay employs an N-order Walsh code to carry additional log_(2)N information bits,which are superimposed onto the SRDCSK signal carrying the decoded source information bits.Subsequently,the superimposed signal carrying both the source and relay information bits is transmitted to the destination.Moreover,the theoretical bit error rate(BER)expressions of the proposed CIMSR-DCSK-CC system are derived over additive white Gaussian noise(AWGN)and multipath Rayleigh fading channels.Compared with the conventional DCSKCC system and SR-DCSK-CC system,the proposed CIM-SR-DCSK-CC system can significantly improve the throughput without deteriorating any BER performance.As a consequence,the proposed system is very promising for the applications of the 6G-enabled lowpower and high-rate communication.

基于混沌理论与DNA动态编码的卫星图像加密算法

针对卫星图像在传输、存储过程中涉及的信息安全问题,该文提出一种新型的基于混沌理论与DNA动态编码的卫星图像加密算法。首先,提出一种改进型无限折叠混沌映射,拓宽了原有无限折叠混沌映射的混沌区间。之后,结合改进型Chebyshev混沌映射与SHA-256哈希算法,生成加密算法的密钥流,提升算法的明文敏感性。然后,利用混沌系统的状态值对Hilbert局部置乱后的像素进行DNA编码,实现DNA动态编码,解决了DNA编码规则较少所带来的容易受到暴力攻击的弱点。最后,使用混沌序列完成进一步混沌加密,从而彻底混淆原始像素信息,增加加密算法的随机性与复杂性,得到密文图像。实验结果表明,该算法具有较好的加密效果和应对各种攻击的能力。

基于两种置乱方式的混合混沌图像加密算法

针对单一混沌系统产生的各伪随机序列之间存在关联性和单一置乱方法置乱效果不佳等问题,提出了一种DNA编码和Zigzag变换两种置乱方式相结合的混合混沌图像加密算法。通过离散的Logistic混沌映射和连续Chen超混沌系统生成混合的混沌伪随机序列,并结合DNA编码和Zigzag两种方法进行联合置乱和扩散,从而实现了混沌图像加密。由于该算法采用Zigzag和DNA编码两种方法进行联合置乱,并采用混合混沌伪随机序列对DNA编码规则和运算规则进行动态选取和控制,增强了置乱和扩散效果,可有效提升图像加密强度。通过仿真验证,并与其他文献进行对比,验证了所提算法的优良性能。

CHAOTIC TRANSDUCER

Utilizing the character of chaos, the sensitivity to the initial conditions, the concept and the structure of so-called chaotic transducer based on Tent map is provided in this paper creatively. The possibility of applying the basic theory of symbolic dynamics to the measurement is presented and proved. Then, the theoretical model of chaotic transducer is realized by using the switched capacitor and the basic experimental results are given. The transducer has such characters as high sensitivity, resolution, the simple structure and combining signal amplification with A/D. The new area of the application of chaos is exploited. Meanwhile, it provides a new method of exploring the structure of new type transducer.

针对电力线通信信道下脉冲噪声的鲁棒混沌传输系统优化设计综述

随着用户的剧增,现有的无线资源已经难以为继。因此,电力线通信(PLC)的重新启用引起了各大研究单位及工业界的关注。PLC由于信道环境复杂,现有处理方案复杂度及成本较高,因而导致其发展缓慢。其中针对脉冲噪声的研究工作最为广泛,如何在低成本情况下针对脉冲噪声实现数据传输的鲁棒性尤为重要。该文首先介绍PLC环境中几种主流噪声以及分类,而后描述具有低成本低复杂度的差分混沌键控(DCSK)及多元DCSK(MDCSK)调制技术。分别介绍与分析该系统在PLC中的特性,以及针对各种脉冲噪声种类存在的优势以及改进方式。其次该文将介绍一些相关编码调制新方案以便于提高带限环境下的传输质量。结果表明这些优化工作显著地改善了系统性能,针对PLC整体信道特性系统参数的调制及编码调制传输优化方案将成为未来工作的研究热点。

抗明文攻击的动态DNA编码数字图像加密算法

针对传统图像加密算法易受明文攻击的问题,提出了结合DNA动态编码和离散混沌系统的数字图像加密算法。首先,选取动力学特性复杂且计算复杂度低的离散混沌系统,为图像密码系统提供优质熵源。接着,设计明文相关机制生成混沌加密序列以抵御选择明文攻击。然后,利用混沌序列对图像比特平面置乱,并依次进行DNA编码、混淆和解码的操作。最后,执行比特平面混淆以获得最终的密文。理论分析和实验结果表明,本文的图像加密算法具有密钥空间大、相邻像素相关性强、直方图统计特性优良等特性,该算法在抵抗明文攻击时的鲁棒性。

基于Julia集和DNA编码的彩色图像加密算法

安全性在图像传输过程中至关重要,为了保证图像信息的安全传输,提出了一种基于Julia集和DNA编码的彩色图像加密算法,该算法使用边界具有混沌性的Julia集作为密钥,并使用幻方置乱对Julia集边界放大区域进行密钥转化,得到密钥图像,结合DNA随机编码对明文图像进行扩散,得到最终密文图像。Julia集密钥仅需要几个简单的参数生成,大大减少了密钥的存储空间。Julia集的混沌性使得密钥随参数的细微修改而发生明显变化,无法正常解密。DNA随机编码有效解决了单一编码方式易受明文攻击的问题。仿真结果表明,论文算法在密钥敏感性、信息熵、抗噪声和差分攻击等方面具有较高的安全性。

Synchronizing Fractional Unified Hyperchaotic System via Impulsive Control

This work investigates synchronization of two fractional unified hyperchaotic systems via impulsive control.The stable theory about impulsive fractional equation is studied based on the stable theory about fractional linear system.Then according to the theorem proposed the sufficient condition on feedback strength and impulsive interval are established to guarantee the synchronization.Numerical simulations show the effectiveness of the theorem.

An efficient chaotic source coding scheme with variable-length blocks

An efficient chaotic source coding scheme operating on variable-length blocks is proposed. With the source message represented by a trajectory in the state space of a chaotic system, data compression is achieved when the dynamical system is adapted to the probability distribution of the source symbols. For infinite-precision computation, the theoretical compression performance of this chaotic coding approach attains that of optimal entropy coding. In finite-precision implementation, it can be realized by encoding variable-length blocks using a piecewise linear chaotic map within the precision of register length. In the decoding process, the bit shift in the register can track the synchronization of the initial value and the corresponding block. Therefore, all the variable-length blocks are decoded correctly. Simulation results show that the proposed scheme performs well with high efficiency and minor compression loss when compared with traditional entropy coding.

基于DNA动态编码和VMP-WFRFT的安全通信方法

为提高物理层信息传输安全,提出一种基于DNA动态编码和变化多参数加权分数傅里叶变换(VMP-WFRFT)的安全通信方法。将DNA编码引入比特置乱,针对现有DNA编码规则少所存在的安全隐患,构造低复杂度四维混沌序列,利用混沌序列随机选择比特矩阵的DNA编码以及运算规则;为进一步掩盖信号调制样式,利用混沌序列动态调整MP-WFRFT参数,从而对调制信号进行VMP-WFRFT变换实现星座的混淆、扩散,同时增强了MP-WFRFT的参数抗扫描能力。仿真结果表明,该方法密钥敏感性良好、密钥空间大,能有效抵御穷举攻击,即使作为加密密钥的混沌初始值仅存在10^(-15)偏差,窃听者的误比特率仍始终保持在0.5左右。

基于小波变换与LDPC码的图像加密

为提高图像的安全性,提出将小波变换、混沌以及LDPC码相结合的图像加密方案。即利用小波变换、混沌对图像进行加密处理,经过小波变换后的系数通过混沌系统产生的序列进行扩散、置乱、组合系数,以显示出加密后的图像,再由LDPC码嵌入水印。利用Matlab进行仿真,结果发现,相较于单一混沌加密而言,该加密方案有着很大的密钥空间,不容易被破解,也能够抵御一些攻击,安全性有所提高。

用于跳频多址通信的混沌跳频码

跳频码的性能对跳频多址通信起着关键性作用。设计具有良好汉明相关和随机性且数量多的跳频码是非常重要的。本文提出一种利用由混沌映射描述的离散混沌系统设计跳频码的新方法。首先由混沌映射产生混沌时间序列，然后利用量化技术对混沌时间序列进行量化，最后由量化后的混沌时间序列产生伪随机跳频码。为了增大混沌跳频码的周期和非线性复杂度，我们利用多个不同混沌映射组成一个级联混沌映射，并用来设计跳频码。实验表明，混沌跳频码具有非常好的性能。

基于滑动相关峰检测的混沌码同步法

混沌无线数字通信是未来高安全高保密无线通信的重要发展方向,而混沌码同步是其核心技术之一。该文根据混沌无线通信特点,提出一种基于滑动相关峰检测的混沌码同步方法。针对非周期混沌码同步,设计了在混沌码同步3个约束条件下的相位延迟控制模块,搭建了基于Logistic序列的同步系统动态模型,并进行了仿真。仿真结果表明,该方法可实现收发两端混沌码同步,同步速度快,抗噪能力强,有效地解决了混沌无线数字通信中的同步方法问题。

一类混沌二相编码脉冲压缩的性能分析

研究了一类混沌信号的二相编码问题。混沌信号对初值非常敏感,能产生大量的二相混沌码,从中可筛选出压缩性能比较好的二相码。在Matlab上的仿真表明,这种二相码具有较高的主副瓣比且数量较多,显示了较好的应用前景。还对该类二相码序列的长度N的大小取值、不同码长的二相码的最大主副瓣比值进行了探讨。分析了长度N、混沌序列初值以及二相码的位数对脉压性能的影响,并给出了最佳结果,可供工程应用参考。因篇幅所限,没有对该类二相码的多普勒性能及脉冲压缩的实现方法作进一步讨论。