一类新型混沌密码序列的理论设计

作者提出了“分段二次非线性映射”。该映射可产生具有均匀分布函数和δ-like自相关函数的混沌序列。与“逐段线性”映射相比,该新映射提供了更强的安全性。     

具有良好安全性能的混沌映射二进制序列

有限精度问题降低了混沌映射序列的密码学和统计特性,且对那些与Tent映射拓扑共轭的映射产生的序列更可通过预测的方法精确重建。本文讨论了混沌映射的拓扑共轭变换及其性质,导出了Tent、Logistic和二阶Chebyshev映射的共轭关系,并针对这种攻击提出了一种混沌序列的产生方法可有效地抵抗这种攻击。     

一种新的TDCS基函数随机相位产生方法及性能分析

针对变换域通信系统对随机相位随机性与相关性的要求,提出了一种采用混沌映射m序列控制法的基函数相位映射方法,相比于传统一维m序列产生基函数,该方法所产生基函数的随机性提高了N倍(N为m序列的长度);同时由于采用混沌映射,产生了大量互相关系数很小的基函数,具有更加良好的相关性。仿真结果表明,采用混沌映射m序列控制法的基函数相位映射方法,提高了基函数的相关性,有效地降低了系统的误码率。     

具有良好安全性能的混沌射二进制序列

有限精度问题降低了混沌射序列的密码学和统计特性，且对那些与Ｔｅｎｔ映射拓扑共轭的映射产生的序列更可通过预测的方法精确重建。本文讨论了混沌映射的拓扑共轭变换及其性质，导出了Ｔｅｎｔ、Ｌｏｇｉｓｔｉｃ和二阶Ｃｈｅｂｙｓｈｅｖ映射的共轭关系，并针对这种攻击提出了一种混沌序列的产生方法可有效地抵抗这种攻击。     

基于双混沌系统的带秘密密钥散列函数构造

在对逐段非线性映射详细分析的基础上,提出一种用逐段非线性映射构造基于扰动的双混沌数字系统方法,然后建立一个基于双混沌系统的带秘密密钥的散列算法,算法以迭代初始点作为秘密密钥,以粗粒化的迭代轨迹作为其散列值。实验结果表明,这种算法具有对初值有高度敏感性、很好的单向性、弱碰撞性,较基于单一混沌映射的散列函数具有更强的保密性能,且实现简单。     

一类混沌映射扩频序列的有限精度实现及其相关性能分析

低维混沌映射序列具有类似白噪声的统计特性，可有效地用作扩频地址码，但有限精度问题影响了它在实际中的应用。本文提出了一种基于素数的拟混沌序列的产生方法能够很好地逼近理想的混沌映射，从而可产生大量具有良好相关性能的序列，对序列统计特性的分析验证了这一点。     

一类混沌映射扩频序列的研究

Logistic混沌映射可产生用于扩频系统的跳频序列。该文用Logistic映射构造了一个二维混沌映射,证明了该二维混沌映射轨道点的概率密度分布,提出了一种混沌跳频序列的产生方法,并通过数值仿真分析了此类扩频序列的奇、偶相关特性和序列码的平衡特性.结果表明:该混沌跳频序列具有良好的性能。     

一种新型的混沌直接扩谱序列

提出了一种基于一维无限折叠混沌映射的直接扩谱序列构造方法。统计测试和仿真结果表明,所产生的二值直接扩谱序为统计独立的均匀分布序列,因而具有理想的二值自相关函数和零互相关函数的特性。     

一种新的基于复合混沌模型的图像加密算法

论文提出了一种新的基于包括Logistic映射模型和混合光学双稳模型的复合混沌系统的图像加密算法。随着对外部密钥的映射,将选择相应的混沌动力系统,产生出混沌序列,对原始图像加密掩盖。计算机仿真的结果表明,混沌序列对外部密钥很敏感。该算法具有良好的运算效率,加密图像具有良好的统计特性。     

基于混沌映射的差分跳频频率编

针对差分跳频系统频率编码及跳频序列的设计问题,提出利用混沌映射构造差分频率编码,并分析了其频率状态转移的Markov性和编译码特点。最后检验了基于混沌映射的差分跳频频率编码的统计性能,结果表明,其产生的跳频序列具有较好的均匀性和随机性,不失为一种具有较高线性复杂度的有效的差分跳频转移函数。     

The design and performance analysis for several new classes ofcodes for optical synchronous CDMA and for arbitrary-medium time-hoppingsynchronous CDMA communication systems

New families of spread-spectrum codes are constructed, that are applicable to optical synchronous code-division multiple-access (CDMA) communications as well as to arbitrary-medium time-hopping synchronous CDMA communications. Proposed constructions are based on the mappings from integer sequences into binary sequences. The authors use the concept of number theoretic quadratic congruences and a subset of Reed-Solomon codes similar to the one utilized in the Welch-Costas frequency-hop (FH) patterns. The properties of the codes are as good as or better than the properties of existing codes for synchronous CDMA communications: both the number of code-sequences within a single code family and the number of code families with good properties are significantly increased when compared to the known code designs. Possible applications are presented. To evaluate the performance of the proposed codes, a new class of hit arrays called cyclical hit arrays is recalled, which give insight into the previously unknown properties of the few classes of number theoretic FH patterns. Cyclical hit arrays and the proposed mappings are used to determine the exact probability distribution functions of random variables that represent interference between users of a time-hopping or optical CDMA system. Expressions for the bit error probability in multi-user CDMA systems are derived as a function of the number of simultaneous CDMA system users, the length of signature sequences and the threshold of a matched filter detector. The performance results are compared with the results for some previously known codes     

半群上的一类陷门单向映射

本文首次给出半群Ｓ上的一类陷门单向映射，基于这类陷门单向映射，选择适当的半群Ｓ，可以建立公钥密码体制。     

嵌套混沌变参映射的构造及分析

文章利用Logistic映射、Henon映射与超混沌M—G系统相互嵌套构造了一类新的变参混沌映射,通过Lyapunov指数方法验证所构造的映射能够产生混沌时间序列,同时分析其输出混沌时间序列的相关性。分析表明,该混沌映射所产生的信号能够用于信息和通信保密系统。     

Coding for a class of nonprobabilistic channels with nonzero memory

A class of finite-alphabet discrete-time nonprobabilistic communication channels with finite nonzero memory is defined. The unknown input/output mapping is required to stay fixed for a specified number of channel uses and then can change arbitrarily within a given set of mappings. The frequency with which the input/output mapping can change gives a rate of time-variation for the channel. The class of channels is parametrized by this rate of time-variation, by alphabet size, by memory duration, and by the set of permissible mappings. Zero-error capacity in the sense of Shannon is computed for a collection of special cases within this class.     

感知哈希综述

 感知哈希(Perceptual Hashing),是多媒体数据集到感知摘要集的一类单向映射,即将具有相同感知内容的多媒体数字表示唯一地映射为一段数字摘要,并满足感知鲁棒性和安全性.感知哈希为多媒体内容识别、检索、认证等信息服务方式提供安全可靠的技术支撑.本文在人类感知模型(Human Perceptual Model)的基础上,明确了感知哈希的定义、性质和一般性描述.并对目前感知哈希的典型算法、应用模式以及评测基准等进行了综述,指出了感知哈希未来的研究方向.     

Statistical analysis of interferometric crosstalk: theory andoptical network examples

General, statistical properties of accumulation of interferometric crosstalk due to a number of interfering signals are analyzed. The probability density function of the total crosstalk is derived as function of the sum of the incoherent crosstalk contributions associated with the interfering signals, Because the total crosstalk level can be expected to vary only slowly as compared to the time duration of one bit, the probability p that the total crosstalk exceeds a maximum tolerable value is introduced as a parameter in the crosstalk and bit error rate analysis of optical networks. General computations show that the crosstalk requirement on optical network elements may be significantly relaxed if it can be accepted that it is possible, although most unlikely, that the total crosstalk may exceed this maximum tolerable value. The statistical crosstalk model is then illustrated by investigation of optical network examples with respect to their crosstalk and transmission properties, and, finally, compared with previous crosstalk models     

Mutual information-based feature extraction on the time-frequencyplane

A method is proposed for automatic extraction of effective features for class separability. It applies to nonstationary processes described only by sample sets of stochastic signals. The extraction is based on time-frequency representations (TFRs) that are potentially suited to the characterization of nonstationarities. The features are defined by parameterized mappings applied to a TFR. These mappings select a region of the time-frequency plane by using a two-dimensional (2-D) parameterized weighting function and provide a standard characteristic in the restricted representation obtained. The features are automatically drawn from the TFR by tuning the weighting function parameters. The extraction is driven to maximize the information brought by the features about the class membership. It uses a mutual information criterion, based on estimated probability distributions. The framework is developed for the extraction of a single feature and extended to several features. A classification scheme adapted to the extracted features is proposed. Finally, some experimental results are given to demonstrate the efficacy of the method     

Approximation of the Karhunen–Loève transformation and its application to colour images

Analysis of colour images in the Red, Green and Blue acquisition space and in the intensity and chrominance spaces shows that colour components are closely correlated (Carron, Ph.D. Thesis, Univ. Savoie, France, 1995; Ocadis, Ph.D. Thesis, Univ. Grenoble, France, 1985). These have to be decorrelated so that each component of the colour image can be studied separately. The Karhunen–Loève transformation provides optimal decorrelation of these colour data. However, this transformation is related to the colour distribution in the image, i.e. to the statistical properties of the colour image and is therefore dependent on the image under analysis. In order to enjoy the advantages of direct, independent and rapid transformation and the advantages of the Karhunen–Loève properties, this paper presents the study of the approximation of the Karhunen–Loève transformation. The approximation is arrived at through exploitation of the properties of Toeplitz matrices. The search for eigenvectors of a Toeplitz matrix shows that complex or real orthogonal mappings such as the discrete Fourier transform and its decompositions approximate the Karhunen–Loève transformation in the case of first-order Markov processes.     

比特交织编码调制(迭代译码)系统标识映射的对称性研究与应用

该文从群论的角度分析了比特交织编码调制(迭代译码)(BICM(-ID))系统中标识映射的对称性。首先给出了标识映射对称性的定义,并指出,二进制标识映射的对称性是BICM(-ID)系统的固有特性,该对称性同构于m阶超立方的对称群。然后基于BICM(-ID)的对称性,提出一种改进的二进制交换算法(IBSA)。该算法的搜索空间为标识映射对称群陪集的代表系。因此,与传统的二进制算法相比,IBSA的搜索效率得到了提高。最后,2维16阶星座图的仿真结果表明,在40000次的运行过程中,IBSA能提高4%的搜索效率;32阶相移键控星座图的仿真结果表明,该算法至少可提高3.5%的搜索效率,单个映射的计算时间缩短了约4000倍。     

基于可Markov分割混沌系统的图像加密算法

为了设计复杂度高、安全性好而计算代价小的图像密码算法,该文从一类新的具有Markov分割性质的混沌系统出发构造了此算法。首先,通过控制此混沌系统的参数并配合时空混沌系统设计了一个密钥流发生器;然后,利用真随机数发生器产生的随机数来扰动系统的初始密钥,以动态生成图像的置换矩阵和加密密钥流;最后,通过利用不同群中的加法混合运算构造扩散函数以增加破译复杂度,以两轮迭代完成了图像加密过程。实验结果表明,此混沌系统产生的密钥流序列有比较好的统计特征,该算法可以破坏原始图像的特征,使得密文图像难以辨识。进一步分析可知,该算法可以很好地抵抗差分分析等其它已知攻击,效率高于一些基于超混沌系统设计的密码算法。此外,此算法计算简单,安全性高,易于实现,具有良好的应用前景。