基于蔡氏电路的通信保密系统的设计(1)

基于蔡氏电路的通信保密系统的设计(1)

混沌理论自上世纪70年代兴起以来于和各学科相互渗透，成为了各个领域内研究的热点。在信息科学高度发达的今天，信息安全也与人们的生活息息相关，信息安全、无损的传输不仅对于军事有重要的意义，对于人们生活的影响也是巨大的。混沌系统所具有的系统对于初始参数、系统参数极为敏感、混沌信号类似噪声等特点均适用于通信保密。利用混沌系统产生的混沌信号对信号进行掩盖保密传输具有可行性与实用性。随着现代科学技术的发展，计算机仿真技术得到广泛的运用使得系统的设计分析更加容易，本文通过采用Multisim以及Matlab仿真技术对混沌电路以及通信保密系统的特性进行验证、分析。

蔡氏电路是混沌理论转化为实际电路模型的典型电路，蔡氏电路具有完整的混沌系统的特性，因此蔡氏电路得到广泛的研究与运用。本文首先通过对蔡氏电路的微分方程组利用Matlab进行数值求解，绘出对应状态变量的相轨迹图。利用Multisim搭建仿真电路原理图，同样绘出相应状态变量的相轨迹图，并与Matlab的结果进行对比，确保仿真原理图所选的元件参数能够满足蔡氏电路微分方程的特性。在Multisim提供的仿真环境下，无法直接观察电感电流的波形图，本文通过串联一个微小电阻，通过观测电阻两侧的电压作为电感电流信号。调整蔡氏电路的参数，研究不同参数下的电路特性，分析系统参数对混沌信号的影响情况。

混沌电路对电路的参数变化极为敏感，为增强通信保密系统的工作稳定性，采用有源元件对无源电感进行等效。对等效后的蔡氏电路的电压信号进行调制、耦合同步等关键技术处理，并对耦合的情况进行分析，以此来说明基于蔡氏电路的通信掩盖保密系统的工作原理，以及信号的耦合同步对于本系统的必要性。

在对完成了电路的改进、信号调制、耦合同步后的主从结构的蔡氏电路，通过增加减法器、反相器等基本模块构成的信号通道的实现传输信号与混沌掩盖保密信号的叠加、消去。为了检验设计的模拟信号的通信保密系统的运行效能及可靠性，选取了正弦信号、chirp电压信号等模拟信号作为测试信号，测试系统对模拟量的保密传输性能；选取了锯齿信号、方波信号作为数字信号的测试信号，测试系统对数字信号的保密传输性能。在测试过程中分别分析了系统正常运行时的原始信号、接收端信号以及在传输通道中得任意位置处的信号。信号保密系统正常工作时在信号接收端，接收的信号与原始传输的信号一致，而在信号传输的任意位置处截获的信号为一任意的随机序列。验证了通信保密系统的良好工作性能，系统从测试信号的结果分析可得，本系统具有可靠性高，电路易于实现等优点。

作为对比，同时分析了在未进行耦合的情况下对应电路参数一致的情况下的信号传输情况，该情况对应了实际运用中电路的参数已经完全泄密的情况。通过分析此种情况下信号的传输特性，估计信号被窃听揭秘的可能。通过分析发现，当未进行耦合时，在通信保密系统信号接收端接收的信号是一个无序的信号序列，这是一个无效的信号序列。因此，即使通信保密系统接收端的参数与混沌信号发射端的数据相匹配依然无法揭秘传输信号。

关键词：混沌理论蔡氏电路 Multisim Matlab 通信保密系统

Abstract

Since chaos theory be come up in the 1970s, it mutual infiltrated with many subjects and become a hot spot of these subjects. With the highly developed of the information science nowadays, information security is very important to people's life. Information transmission security and without a distortion is not only very important for military, but also has an important significance in people's life. As a chaos system is very sensitive to the initial parameters of the system, a tiny parameters of the system changed has a huge influence to chaos signal and the chaotic signal is similar to the noise, so chaos system is very suitable be used for communication security. Using a chaos system to produce a chaotic signal to cover the signal that need to transmission is feasible and practical. With the development of modern science and technology, computer simulation technology is much more widely using of the system design and analysis, this paper using Matlab® and Multisim® to verify and analysis the circuit's and system's characteristics.

Chua's circuit is the model circuit of the chaos theory transform into practical circuit, Chua's circuit has all the characteristics of a chaos system. Therefore Chua's circuit is widely researched and applied. This paper using Matlab® to solve the Chua's circuit's differential equations and draw corresponding state variable phase track diagram. Using Multisim® to build the simulation circuit principle diagram and draw the same state variable phase track diagram as Matlab's. Comparing the results of the Matlab® simulation with the MUltisim®'s, to ensure that the principle diagram of the selected device parameters can meet the Chua circuit differential equation of characteristics. In Multisim® provide simulation environment, it can't be directly observed inductance current waveform diagram, series a small resistance in order to change the inductance current to the voltage on both sides of the resistance. Changing the parameters of the Chua circuit, research the circuit characteristics under different parameters, analysis the system parameters' influence to the chaotic signal.

Being sensitive to the system parameters, the inductance are replace by the active element to make the system more stable. Modulation, coupling, and other key technology are processing in the new circuit. Analyzing the coupling of the situation to explain how the communication hide secret system based on Chua circuit works, and the coupling for communication security system of necessity.

After finishing improvement, modulation, coupling of the Master/Slaver Chua circuit, by increasing the subtracted, inverter and signal channel basic module to realize the transmission signal and chaos masking secret signal superposition and elimination. In order to test the paper presents the design of analog signal communication security system operation efficiency and reliability, the selection of the sine signal, chirp voltage signal as a test signal, the testing system of secrecy transmission performance. In the test process separately