Henon CSK Secure Communication System Using Chaotic Turbo Codes

In this paper, the authors design a novel chaotic secure communication system, which has high security and good error correcting capability. Firstly, the Henon Chaos Shift Keying (CSK) modulation block is presented. Secondly, chaotic turbo encoder/decoder (hard decision) is introduced. Thirdly, this chaotic secure communication system, which comprises the Henon CSK modulation block and chaotic turbo encoder in a serially concatenated form, is shown. Furthermore, a novel two step encryption scheme is proposed, which is based on the chaotic turbo encoded Henon CSK secure communication system.

基于空时分组/混沌编码的多天线多基频通信编码研究

为了优化空时分组编码(STBC)和混沌编码,提升无线通信的性能与可靠性,采用多基频混沌编码(MFCC)结合空时分组编码技术搭建了一种双重编码模型,并对该模型的编码解码性能进行仿真分析,评估模型的编码解码性能。实验结果显示,当信噪比为10 dB时,新模型的误码率低至10-8,并且能在两基频条件下实现3548 b/s的高吞吐量。表明该编码解码模型不仅能降低误码率,还能有效提高基频的吞吐量,为促进无线通信技术的发展提供了有力支持。

基于长度可变密钥的光学图像加密方法

为提升光学图像加密效果,设计了一种基于长度可变密钥的光学图像加密方法。基于混沌方程构成混沌序列均匀化普适算法,运用该算法生成均匀化伪随机序列,以此作为长度可变密钥,经空间光调制器调制后,转换此类密钥为伪随机相位掩模(PRPM),运用两个转换后PRPM双重随机相位编码初始光学图像,并结合变形分数傅里叶变换(AFrFT),相位转换编码后光学图像,获得加密光学图像,完成光学图像加密。实验结果显示,该方法可针对不同光学图像生成敏感性与唯一性密钥,实现不同光学图像的加密处理,加密效果显著,加密光学图像的像素频数分布均匀,且解密后光学图像与初始光学图像几乎一致,整体加解密效果理想,可有效保障光学图像的安全性,而且本方法可以在最短3 s的时间内完成光学图像的加密和解密,加解密效率更高,综合效果更佳。

基于小波压缩深度学习重构的多图像光学加密

为解决多图像加密算法密文体积大、加密效果差、重构效果不理想等问题,提出一种基于小波压缩和深度学习重构的多图像光学加密方法。利用小波压缩提取多图像的低频部分,将重排后的新图放入改进的FDT-DRPE光学加密系统中得到密文;利用矢量分解和螺旋相位变换克服FDT-DRPE不敏感问题;构造的L_S混沌系统提高密钥敏感性。提出新型深度学习网络模型BHCN,解决传统图像重构精度不高问题。实验结果表明,密文体积可压缩至原图的1/4,重构图像的峰值信噪比为34.57 dB,结构相似性为0.9521,与同类文献相比,速度更快,重构效果更好,安全性更高。

基于四维混沌系统的彩色图像加密算法

图像加密算法研究在确保图像信息安全方面至关重要,图像中包含的信息量较大,相邻像素间存在较强的关联性,在传输过程中容易造成信息泄露。为了打破图像相邻像素间较强的关联性以及提高抗攻击性,提出了基于四维混沌系统DNA编码的彩色图像加密算法。采用四维混沌系统模型产生混沌序列,利用产生的混沌序列和DNA编码等方法对加密图像进行置乱处理,最后对图像加密效果和抗攻击性能进行对比验证。仿真结果表明,通过该算法对图像加密后,相邻像素间的关联性大大削弱。相较于对比算法,该算法能够对彩色明文图像进行有效的加密,同时算法具备抵御干扰和攻击的能力,显著提高了图像的安全性,在彩色图像加密领域具有一定的发展前景。

一类多涡卷Chua系统及其在图像加密中的应用

为使混沌序列表现出更复杂的特性,在典型的Chua系统上引入了分段线性函数,使所得的系统产生可控数量的多涡卷吸引子。对该系统进行动力学分析,分析结果表明,该系统混沌特性分布广泛,具有丰富的动力学行为。在此基础上,提出了一种基于Zigzag置乱和DNA编码的加密算法,并从多个方面对该算法的安全性进行了分析。仿真结果验证了该方法不仅能对图像进行有效加密,而且能有效抵抗各种常见的攻击,为图像加密提供了理论依据。

一种时间反转的参考信号调制DCSK通信方案

针对DCSK系统信息传输速率低及安全性差的问题,提出一种时间反转参考信号调制DCSK(TR-RMDCSK)通信系统方案。该方案采用RM调制实现了在一个帧时隙传输两个比特,携带偶数信息比特的混沌信号既是信息信号,也是传输奇数信息比特的参考信号,将参考信号进行时间反转,消除了同一帧时隙信号间的相关性,提升了比特传输速率及信号保密性。推导了高斯信道下的理论误码率,并在高斯信道和莱斯信道下进行了性能仿真分析。结果表明,该方案在不牺牲传输速率的情况下改善了误码性能,提高了系统安全性。

基于SSTDR的电缆故障定位方法

由于当前电缆大都铺设在地下,一旦发生故障,检修人员若不能及时发现,将影响电网正常供电,因此检修人员须要提前定位电缆故障发生的位置。文章提出了一种基于改进扩展频谱时域反射法(Spread Spectrum Time-Domain Reflectometry,SSTDR)的电缆故障定位方法。文章介绍了SSTDR在线检测电缆故障测距原理、定位原理、PN码的选取以及故障定位算法;提出了以Logistic混沌序列作为入射信号对电缆故障进行定位的方法。基于MATLAB/Simulink平台搭建调制电路模型进行仿真分析,根据所生成二值化的Logistic混沌序列以及电缆开路故障波形,文章验证了所提方法具有一定的工程应用价值。

基于T-Chaotic映射的保奇偶对称交织器

提出了基于T-Chaotic映射的保奇偶对称交织器算法(TCOP)。通过引入混沌模型,可以提高交织器的可控随机性以及减少保奇偶设计过程中校验序列的相关性;保奇偶对称设计则提高了校验序列的等差保护并简化了系统结构。提出了3种TCOP算法,并与S-Chaotic算法和基于S-Chaotic映射的保奇偶交织器设计(SCOP)在时间延迟和误比特率上进行了比较。在时延方面,帧长范围为512～4096,S-Chaotic的生成时间是TCOP.2的8～676倍,SCOP是TCOP.2的8～118倍;在固定帧长(1024)下,TCOP.2与SCOP性能相近,比S-Chaotic提高了约0.3dB的编码增益。

Repeater jamming suppression method for pulse Doppler fuze based on identity recognition and chaotic encryption

Pulse Doppler(PD) fuze is widely used in current battlefield. However, with the threat of repeater jamming, especially digital radio frequency memory technology, the deficiency in the anti-repeater jamming of a traditional PD fuze increasingly emerges. Therefore, a repeater jamming suppression method for a PD fuze based on identity(ID) recognition and chaotic encryption is proposed. Every fuze has its own ID which is encrypted with different chaotic binary sequences in every pulse period of the transmitted signal. The thumbtack-shaped ambiguity function shows a good resolution and distance cutoff characteristic. The ability of anti-repeater jamming is emphatically analyzed, and the results at different signal-to-noise ratio(SNR) show a strong anti-repeater jamming ability and range resolution that the proposed method possesses. Furthermore, the anti-repeater jamming ability is influenced by processing gain, bit error rate(BER) and correlation function. The simulation result validates the theoretical analysis, it shows the proposed method can significantly improve the anti-repeater jamming ability of a PD fuze.

New chaotical image encryption algorithm based on Fisher–Yatess scrambling and DNA coding

Based on the Fisher–Yatess scrambling and DNA coding technology, a chaotical image encryption method is proposed. First, the SHA-3 algorithm is used to calculate the hash value of the initial password, which is used as the initial value of the chaotic system. Second, the chaotic sequence and Fisher–Yatess scrambling are used to scramble the plaintext,and a sorting scrambling algorithm is used for secondary scrambling. Then, the chaotic sequence and DNA coding rules are used to change the plaintext pixel values, which makes the ciphertext more random and resistant to attacks, and thus ensures that the encrypted ciphertext is more secure. Finally, we add plaintext statistics for pixel-level diffusion to ensure plaintext sensitivity. The experimental results and security analysis show that the new algorithm has a good encryption effect and speed, and can also resist common attacks.

A novel chaotic stream cipher and its application to palmprint template protection

Based on a coupled nonlinear dynamic filter （NDF）, a novel chaotic stream cipher is presented in this paper and employed to protect palmprint templates. The chaotic pseudorandom bit generator （PRBG） based on a coupled NDF, which is constructed in an inverse flow, can generate multiple bits at one iteration and satisfy the security requirement of cipher design. Then, the stream cipher is employed to generate cancelable competitive code palmprint biometrics for template protection. The proposed cancelable palmprint authentication system depends on two factors： the palmprint biometric and the password/token. Therefore, the system provides high-confidence and also protects the user＇s privacy. The experimental results of verification on the Hong Kong PolyU Palmprint Database show that the proposed approach has a large template re-issuance ability and the equal error rate can achieve 0.02%. The performance of the palmprint template protection scheme proves the good practicability and security of the proposed stream cipher.

A Novel Concatenated Chaotic Communication System

A strategy for a novel concatenated chaotic communication system is presented. The transmitter system comprises chaotic turbo encoder and logistic CSK block in a serially concatenated form. Chaotic turbo code is capable of reducing bit error rate (BER) of the chaotic system in the AWGN channel. Through the chaotic turbo encoder, the coded sequence, which has quasi-chaotic properties, will be transmitted into the logistic CSK block. Having a very sensitive dependence on initial conditions of the map, the logistic CSK block can also be taken as the chaotic authentication method. The receiver, which has logistic demodulation block and chaotic decoder, is a linear asymptotic approximation to the inverse of the transmitter system. A chaotic iterative soft-decision decoding algorithm is also developed based on conventional maximum A posteriori decoding algorithm. At last, a two-step authentication method of this chaotic system is also presented.

Performance analysis of quantum access network using code division multiple access model

A quantum access network has been implemented by frequency division multiple access and time division multiple access, while code division multiple access is limited for its difficulty to realize the orthogonality of the code. Recently,the chaotic phase shifters were proposed to guarantee the orthogonality by different chaotic signals and spread the spectral content of the quantum states. In this letter, we propose to implement the code division multiple access quantum network by using chaotic phase shifters and synchronization. Due to the orthogonality of the different chaotic phase shifter, every pair of users can faithfully transmit quantum information through a common channel and have little crosstalk between different users. Meanwhile, the broadband spectra of chaotic signals efficiently help the quantum states to defend against channel loss and noise.

Implementation of LT codes based on chaos

Fountain codes provide an efficient way to transfer information over erasure channels like the Internet. LT codes are the first codes fully realizing the digital fountain concept. They are asymptotically optimal rateless erasure codes with highly efficient encoding and decoding algorithms. In theory, for each encoding symbol of LT codes, its degree is randomly chosen according to a predetermined degree distribution, and its neighbours used to generate that encoding symbol are chosen uniformly at random. Practical implementation of LT codes usually realizes the randomness through pseudo-randomness number generator like linear congruential method. This paper applies the pseudo-randomness of chaotic sequence in the implementation of LT codes. Two Kent chaotic maps are used to determine the degree and neighbour（s） of each encoding symbol. It is shown that the implemented LT codes based on chaos perform better than the LT codes implemented by the traditional pseudo-randomness number generator.

基于混沌加密的QR码彩色图像复合水印算法

本研究提出了一种基于NSCT-DWT-SVD复合的QR码混沌加密彩色图像水印算法。首先将“飞行学院”四字组成的水印图像通过编码器进行QR编码生成QR码水印信息,再对水印进行Logistic混沌映射加密,将RGB颜色模型的原载体图像转换成YUV颜色模型图像,对转换后的模型Y分量进行提取,将其进行NSCT生成低频分量,随后进行小波变换及SVD奇异值分解获得奇异值,最后将加密的QR码通过加性原理叠加到分解后的奇异值上。通过实验证明,该算法得到的峰值PSNR为52.15dB,保证了嵌入水印的信息量及隐蔽性,对椒盐噪音、JPEG压缩攻击NC值都为1,尤其是由于加入NSCT保证了图像的平移不变性,SVD更是提高了算法抵抗旋转攻击的能力。

Design of Digital Hybrid Chaotic Sequence Generator

The feasibility of the hybrid chaotic sequences as the spreading codes in code divided multiple access(CDMA) system is analyzed. The design and realization of the digital hybrid chaotic sequence generator by very high speed integrated circuit hardware description language(VHDL) are described. A valid hazard canceledl method is presented. Computer simulations show that the stable digital sequence waveforms can be produced. The correlations of the digital hybrid chaotic sequences are compared with those of m-sequences. The results show that the correlations of the digital hybrid chaotic sequences are almost as good as those of m-sequences. The works in this paper explored a road for the practical applications of chaos.

一种动态密钥与DNA交错编码的多图像加密算法

针对目前多图像加密算法中置乱效果不佳、DNA编码模式固定及密钥更新方式实用性低等问题,提出了一种基于动态密钥更新与DNA动态交错编码的加密方案。首先,设计了一种利用SHA-256的动态密钥更新方案,通过限制新密钥中的明文信息量摆脱一次一密的密钥系统。其次,改进了三维循环移位置乱方法,并以此降低明文中的相关性。随后,根据混沌序列动态选取DNA编码规则及编码顺序,并在此基础上将图像矩阵逐像素动态交错编码为DNA序列。最后,将编码后的DNA序列与给定序列进行碱基运算完成对明文图像的加密。仿真实验表明,该算法密文图像的相关性可低至10-3,全局信息熵可达7.9994。该算法能抵挡各种攻击方式,具有较高安全性。

基于DNA编码和混沌系统的语音加密算法

提出了一种基于DNA编码和混沌系统的语音加密算法。该算法首先将原始语音分成两个部分,利用Lorenz混沌系统生成的混沌序列,分别对第一部分语音做动态DNA编码和异或运算,对第二部分语音做异或运算,以实现语音数据的扩散;其次利用Logistic混沌系统生成的混沌序列将扩散后的语音索引置乱,再对置乱后语音的极性置乱,使得样本值的直方图的分布更为均匀。仿真结果和理论分析表明,该加密算法具有密钥空间大、密钥灵敏度高、抗穷举攻击、统计攻击和选择明文攻击能力强等优点。

结合脉冲位置调制的正交多用户混沌通信系统

提出一种基于Walsh码序列的脉冲位置调制差分混沌键控通信系统(A Pulse Position Modulated Differential Chaotic Keying Communication System Based on Walsh Code Sequences,PPM-DCSK-WC)。利用Walsh码的正交性实现多用户传输,避免了用户间干扰对系统误码性能产生影响,提高系统的数据安全性,也大大提升了系统的传输速率,同时也具备了脉冲位置调制差分混沌键控通信系统(PPM-DCSK)的误码率性能优势。仿真结果表明,在多径瑞利衰落信道上,当误码率水平为10^(-3)时,PPM-DCSK-WC多用户方案的误码率比传统多用户方案提高了4 dB,在高时延扩展信道上性能增益更是能达到6 dB。该系统被认为是一种优秀的多用户短距离无线通信系统。