基于广义混沌映射切换的混沌同步保密通信

提出了一种基于广义混沌映射切换的混沌同步保密通信方式.这种通信方式首先构建产生多种混沌序列的广义混沌映射模型,然后在不同时段根据切换策略产生不同混沌序列,在发送端,将信号与混沌载波之和取模运算后再嵌入混沌映射的输入端进行迭代运算以实现调制;在接收端,根据切换协议,用同一个相应的广义混沌映射模型从接收信号中提取混沌载波并进而恢复信息信号.研究结果表明:这种基于广义混沌映射切换的混沌同步通信方式比基于单一混沌系统的保密通信方式具有更强的抗干扰能力,保密性能更好,且实现简单. 关键词： 混沌 混沌映射切换 同步 保密通信     

Decoding information by following parameter modulation with parameter adaptive control

It has been proposed to realize secure communication using chaotic synchronization via transmission of a binary message encoded by parameter modulation in the chaotic system. This paper considers the use of parameter adaptive control techniques to extract the message, based on the assumptions that we know the equation form of the chaotic system in the transmitter but do not have access to the precise values of the parameters which are kept secret as a secure set. In the case in which a synchronizing system can be constructed using parameter adaptive control by the transmitted signal and the synchronization is robust to parameter mismatches, the parameter modulation can be revealed and the message decoded without resorting to exact parameter values in the secure set. A practical local Lyapunov function method for designing parameter adaptive control rules based on originally synchronized systems is presented.     

光学双稳系统混沌驱动保密通讯原理研究

根据声光双稳系统混沌驱动下的动力学行为，提出利用系统的相位特性实现信息的混沌加密，并且由接收端混沌驱动产生的混沌信号完成信息提取的原理。发现在较大的噪声覆盖下仍然可以实现信息的安全传送，由于信息解密不需要与载波安全同步的混信号而只利用传输信号与接收端被驱动系统输出信号的相位关系，因此这种方法具有实际应用价值。     

Chaotic secure communication based on strong tracking filtering

A scheme for implementing secure communication based on chaotic maps and strong tracking filter (STF) is presented, and a modified STF algorithm with message estimation is developed for the special requirement of chaotic secure communication. At the emitter, the message symbol is modulated by chaotic mapping and is output through a nonlinear function. At the receiver, the driving signal is received and the message symbol is recovered dynamically by the STF with estimation of message symbol. Simulation results of Holmes map demonstrate that when message symbols are binary codes, STF can effectively recover the codes of the message from the noisy chaotic signals. Compared with the extended Kalman filter (EKF), STF has a lower bit error rate.     

New communication schemes based on adaptive synchronization

In this paper, adaptive synchronization with unknown parameters is discussed for a unified chaotic system by using the Lyapunov method and the adaptive control approach. Some communication schemes, including chaotic masking, chaotic modulation, and chaotic shift key strategies, are then proposed based on the modified adaptive method. The transmitted signal is masked by chaotic signal or modulated into the system, which effectively blurs the constructed return map and can resist this return map attack. The driving system with unknown parameters and functions is almost completely unknown to the attackers, so it is more secure to apply this method into the communication. Finally, some simulation examples based on the proposed communication schemes and some cryptanalysis works are also given to verify the theoretical analysis in this paper.     

适合传输快变信息信号的混沌调制保密通信

提出一种新的混沌调制通信方法.利用一个自适应控制器跟踪信息信号的误差对产生混沌载波的发射系统进行参数调制.同时，信息信号直接与混沌载波相乘作为发射信号驱动接收系统.在接收端，另一个自适应控制器维持收发系统的混沌同步并恢复出信息信号.由于同步误差与信息信号无关，从而实现了大幅度、快时变信息信号的混沌调制通信.理论分析和数值模拟的结果表明该方法增强了低维混沌系统的通信保密性. 关键词： 混沌调制 保密通信 自适应控制器 蔡氏电路     

Secure communication based on a four-wing chaotic system subject to disturbance inputs

In this paper, a two-input two-output secure communication scheme based on a four-wing four-dimensional chaotic system with disturbance inputs is discussed. Based on parameter modulation theory and Lyapunov stability theory, synchronization and secure communication between transmitter and receiver are achieved and two message signals are recovered via a convenient robust high-order sliding mode adaptative controller. In addition, the gains of the receiver system can be adjusted continually, the unknown parameters can be identified precisely and the disturbance inputs can be suppressed simultaneously by the proposed adaptative controller. Synchronization under the effect of noise is also considered. Computer simulations are done to verify the proposed methods and the numerical results show that the obtained theoretic results are feasible and efficient.     

一种基于强跟踪滤波的混沌保密通信方法

提出了一种基于强跟踪滤波器的混沌保密通信方法. 在发送端, 混沌映射和信息符号被建模成非线性状态空间模型, 信息符号被加性混沌掩盖或乘性混沌掩盖调制, 然后通过信道输出. 在接收端, 驱动信号被接收, 使用带有贝叶斯分类器(信息符号估计)的强跟踪滤波器算法动态地恢复信息符号. Logistic混沌映射的仿真表明, 当信息符号为二进制编码时, 不管是加性混沌掩盖调制还是乘性混沌掩盖调制, 强跟踪滤波器均能较好地从混沌信号中恢复信息符号. 与扩展卡尔曼滤波器相比, 由于卡尔曼滤波器对于离散的信息符号跟踪能力差, 混沌映射中信息符号难以恢复, 比特误码率高. 因此, 这种基于强跟踪滤波器的混沌保密通信方法是有效的.     

Adaptive synchronization of a switching system and its applications to secure communications

This paper studies the adaptive synchronization of a switching system with unknown parameters which switches between the R?ssler system and a unified chaotic system. Using the Lyapunov stability theory and adaptive control method, the receiver system will achieve synchronization with the drive system and the unknown parameters would be estimated by the receiver. Then the proposed switching system is used for secure communications based on the communication schemes including chaotic masking, chaotic modulation, and chaotic shift key strategies. Since the system switches between two chaotic systems and the parameters are almost unknown, it is more difficult for the intruder to extract the useful message from the transmission channel. In addition, two new schemes in which the chaotic signal used to mask (or modulate) the transmitted signal switches between two components of a chaotic system are also presented. Finally, some simulation results are given to show the effectiveness of the proposed communication schemes.     

A new chaotic communication scheme based on adaptive synchronization

A new chaotic communication scheme using adaptive synchronization technique of two unified chaotic systems is proposed. Different from the existing secure communication methods, the transmitted signal is modulated into the parameter of chaotic systems. The adaptive synchronization technique is used to synchronize two identical chaotic systems embedded in the transmitter and the receiver. It is assumed that the parameter of the receiver system is unknown. Based on the Lyapunov stability theory, an adaptive control law is derived to make the states of two identical unified chaotic systems with unknown system parameters asymptotically synchronized; thus the parameter of the receiver system is identified. Then the recovery of the original information signal in the receiver is successfully achieved on the basis of the estimated parameter. It is noticed that the time required for recovering the information signal and the accuracy of the recovered signal very sensitively depends on the frequency of the information signal. Numerical results have verified the effectiveness of the proposed scheme.     

Application of periodic orbit theory in chaos-based security analysis

Chaos-based encryption schemes have been studied extensively, while the security analysis methods for them are still problems to be resolved. Based on the periodic orbit theory, this paper proposes a novel security analysis method. The periodic orbits theory indicates that the fundamental frequency of the spiraling orbits is the natural frequency of associated linearized system, which is decided by the parameters of the chaotic system. Thus, it is possible to recover the plaintext of secure communication systems based on chaotic shift keying by getting the average time on the spiraling orbits. Analysis and simulation results show that the security analysis method can break chaos shift keying secure communication systems, which use the parameters as keys.     

光纤混沌双芯双向保密通信系统研究

把量子阱激光混沌耦合反馈同步系统应用于光纤保密通信中,提出光纤混沌双芯双向保密通信设想.通过耦合外部光注入多量子阱激光混沌全光耦合反馈同步系统和光纤传输信道,建立了光纤混沌双芯双向通信系统物理模型.理论和数值证明了激光混沌同步,理论分析指出光纤中的自相位调制是限制激光混沌在光纤传输中同步的主要原因,并推导出混沌信号双芯双向传输中的非线性相移以及混沌激光功率限制和传输距离公式.数值实现了该系统在长距离二根光纤传输中的同步,详细地分析了系统同步时间随光纤传输长度的关系.模拟了调制频率06 GHz的混沌模拟通 关键词： 混沌 同步 光纤 保密通信     

Dispersion compensation in an open-loop all-optical chaotic communication system

The optical chaotic communication system using open-loop fiber transmission is studied under strong injection conditions. The optical chaotic communication system with open-loop configuration is studied using fiber transmission under strong injection conditions. The performances of fiber links composed of two types of fiber segments in different dispersion compensation maps are compared by testing the quality of the recovered message with different bit rates and encrypted by chaotic modulation (CM) or chaotic shift keying (CSK). The result indicates that the performance of the pre-compensation map is always worst. Two types of symmetrical maps are identical whatever the encryption method and bit-rate of message are. For the transmitting and the recovering of message of lower bit rate (1 Gb/s), the post-compensation map is the best scheme. However, for the message of higher bit rate (2.5 Gb/s), the parameters in communication system need to be modified properly in order to adapt to the high-speed application. Meanwhile, two types of symmetrical maps are the best scheme. In addition, the CM method is superior to the CSK method for high-speed applications. It is in accordance with the result in a back-to-back configuration system.     

Synchronization of randomly multiplexed chaotic systems with application to communication

Synchronized chaotic systems have recently been applied to the area of secure communications in a variety of ways. At the same time, there have also been significant advances in deciphering messages masked by chaotic signals. It is important, therefore, to explore more secure approaches to using chaos in communication. We show that multiple chaotic systems can be synchronized through a scalar coupling which carries a stochastic signal generated by random multiplexing of the source systems. This approach, which is a variant of the active-passive decomposition method, promises enhanced security in chaos-based communication.     

一种新型的双向长距离光纤混沌保密 通信系统性能研究

基于两个在驱动混沌信号注入下的响应半导体激光器之间的混沌同步, 提出了一种新型的可实现信息双向、长距离保密传输的系统, 并建立了相应的理论模型. 利用该理论模型, 研究了系统的双向传输性能、 安全性能以及系统性能随传输距离的变化. 结果表明: 两个响应激光器在受到发自同一驱动混沌激光器的混沌光注入下, 其混沌输出虽然与注入混沌信号相差很大, 但两个响应激光器的混沌输出却能实现非常好的无时间延迟的等时同步; 对窃听者可能获取信息的各个途径进行了考察, 结果显示该系统具有很好的安全性; 采用普通单模光纤作为传输信道, 信息经过50 km传输后, 解调信息Q因子可达到6以上; 采用色散位移光纤, 信息经过200 km的传输, 解调信息Q因子还可达6以上.     

开环全光混沌通信系统中的光纤信道结构

根据外光反馈半导体激光器及光纤传输方程,构建了基于光纤信道的开环全光混沌通信系统.考虑混沌调制和混沌键控两种信息加密方法,采用先进的校正相减解调法恢复信息,并且通过解调Q因子衡量系统性能.以不同次序排列单模光纤和色散补偿光纤构成4种结构的光纤信道,通过数值仿真分析信道结构对系统通信性能的影响.结果表明,为光纤信道保留少量的负累积色散有利于改善远程传输性能;两端补偿和中间补偿这两种对称结构的性能一致,对称结构优于非对称结构即预补偿和后补偿,适用于远程高速开环全光混沌通信.另外,无论光纤信道结构怎样,在远程高速激光混沌通信中混沌调制方法总是优于混沌键控方法.     

Generation of higher degree chaos by controlling harmonics of the modulating signal in EDFRL

Erbium doped fiber ring lasers (EDFRL) are being used to generate optical chaos for secure communication by modulating the cavity loss/pump power or exploiting nonlinearities. The security level in chaotic communication depends on degree of chaos quantified by the Lyapunov exponent and its variability which is determined by the number of tuneable system parameters which were limited to five main parameters, i.e. modulation index, modulation frequency, pump power, cavity gain and loss. In this study we have increased the number of tuneable parameters using square, triangular and sum of harmonics waveforms. We have analysed the effect on degree of chaos of phase and duty cycle of square modulating signal with gradual addition of harmonics. For the given cavity parameters, the Lyapunov exponents can be increased by more than fifteen times using square wave modulating signal and a duty cycle of 60%. The electrical parameters identified make generation of new chaotic sequences more flexible in a field deployed EDFRL chaotic system.     

开环全光混沌通信系统中的光纤信道结构

根据外光反馈半导体激光器及光纤传输方程,构建了基于光纤信道的开环全光混沌通信系统.考虑混沌调制和混沌键控两种信息加密方法,采用先进的校正相减解调法恢复信息,并且通过解调Q因子衡量系统性能.以不同次序排列单模光纤和色散补偿光纤构成4种结构的光纤信道,通过数值仿真分析信道结构对系统通信性能的影响.结果表明,为光纤信道保留少量的负累积色散有利于改善远程传输性能;两端补偿和中间补偿这两种对称结构的性能一致,对称结构优于非对称结构即预补偿和后补偿,适用于远程高速开环全光混沌通信.另外,无论光纤信道结构怎样,在远程高速激光混沌通信中混沌调制方法总是优于混沌键控方法.     

Parameter adaptation technique for rapid synchronization and secure communication

An effort is made here to show how parameter adaptation can be used for achieving rapid synchronization between two chaotic systems in a time much smaller than the time scale of chaotic oscillations. This rapid synchronization can be used for faster and more secure communication of digital messages. Different symbols of the message are coded by assigning different values to a parameter set. At the receiving end the parameter values quickly adapt to the changing transmitter parameters, thereby permitting the messages to be decoded. The technique presented here is significantly more secure compared to other similar schemes because in our scheme the transmitting parameters change so rapidly that an intruder cannot infer any information about the attractors corresponding to the different parameter values. Another feature, which enhances security, is that a subsystem of the transmitter can be changed, without having to convey this information to the bona fide recipient. Thus for the same plaintext and the same key, several different cipher-texts can be generated. Further, the variables, whose evolution equations contain the coding parameters, are not transmitted.     

Adaptive strategies for recognition,noise filtering,control, synchronization and targeting of chaos

Combining knowledge of the local variation rates with some information on the long time trends of a dynamical system, we introduce an adaptive recognition technique consisting in a sequence of variable resolution observation intervals at which the geometrical positions are sampled. The sampling times are chosen so that the sequence of observed points forms a regularized set, in the sense that the separation of adjacent points is almost uniform. We show how this adaptive technique is able to recognize the unstable periodic orbits embedded within a chaotic attractor and stabilize anyone of them even in the presence of noise, through small additive corrections to the dynamics. These techniques have been applied to the synchronization of three chaotic systems, assuring secure communication between a message sender and a message receiver; furthermore they provide robust solutions to the problems of targeting of chaos and of filtering the noise out of an experimental chaotic data set. Implementation of adaptive methods to chaotic Lorenz, three and four dimensional Roessler models and Mackey-Glass delayed system are reported.(c) 1997 American Institute of Physics.