【作者】 肖要强；

【导师】 王玲；

【作者基本信息】 湖南师范大学 ， 电路与系统， 2005， 硕士

【摘要】 混沌现象作为非线性动力系统中一种确定的类随机过程,广泛存在于客观世界中。由于混沌动力系统对初始条件的极端敏感性,而能产生大量的非周期、连续宽带频谱、似噪声且可再生的混沌信号,使它具有天然的隐蔽性,再加上混沌信号的长期不可预测性,高复杂性和易于实现,对该问题的研究,将具有十分重要的理论意义和实际应用价值,混沌理论的应用已成为目前国内外关注的学术热点和前沿课题。 本文围绕混沌技术在现代保密通信中的应用这一课题进行了较为深入的研究,所得的新成果主要包括: 1.研究了码分多址(CDMA)通信系统中应用的伪随机序列技术,主要包括混沌直扩序列的产生和性能分析。文章提出了一种改进的混沌映射——变参Tent混沌映射,由于此映射的分形参数在演化过程中不断变化,从而能进一步加强通信系统的保密性。并就此提出了一种新型的混沌扩频序列——变参Tent混沌扩频序列,对所产生的扩频序列的伪随机性能进行了计算和仿真,结果表明所提出的混沌序列具有优良的伪随机特性。随后,研究了变参Tent混沌扩频序列和Tent混沌扩频序列在直扩CDMA系统的应用情况,并进行了仿真,发现变参Tent混沌扩频序列有较好的抗多用户干扰和抗多径干扰能力,进一步验证提出的新混沌扩频序列确实具有优良的性能,从而证明了此混沌序列作为扩频序列的可行性。 2.研究了超混沌信号在活动图像加解密技术中的应用,着重探索了一种如何利用超混沌技术对活动图像的加解密方法,阐述了怎样用多维微分方程得到超混沌序列,进而详细的论述了加密矩阵的实现,用产生的加密矩阵随机的改变每一帧图像的每一个像素,并利用图像置乱变换技术来实现对活动图像的加密的目的。从Shanon证明的一次一密的密码体制不可破译的原理来看,利用此加解密技术对活动图像加密与解密具有安全性和高效性,从计算机仿真来看,结果表明此方法是切实可行的。更多还原

【Abstract】 As a random-like phenomenon in non-linear deterministic dynamical system, Chaos widely exists in the real world. Because chaos is extremely sensitive to initial conditions of the chaotic system, and a large number of non-periodic, continuous broadband frequency spectrum, noise-like, yet deterministic and reproducible signals can be generated, it has natural concealment. What’s more, chaotic signals can’t be forecast for a long term, and it is very complicated, and easily realized, the application of chaos theory has been one of important issues and forefront project. Based on applications of chaotic technology in contemporary secure communication, some deeper researches has been performed, the following innovative results are given:1. The PN sequence of CDMA communication system is focused in the thesis, mainly including generation and performance analysis of chaos direct spread sequences. Firstly, an improved chaos map (varying-parameter Tent chaos map) is put forward. Owing to the bifurcation parameter varied in a limited range, and chaos is sensitive to initial condition, the security of communication system is greatly enhanced. And a kind of new chaotic spread-spectrum sequence is presented, the performance of PN code is calculated and simulated. Results show the chaotic spread-spectrum sequence has good properties. Then, both varying-parameter Tent chaotic sequence and Tent chaotic sequence are applied to the model of direct spread CDMA system and the error rate of system is demonstrated, the simulation results further indicate that the multiple-access interferences (MAI) from other users and the multiple-path interference (MPI) using the presented chaotic sequence are very small, they can be used as spread-spectrum sequence because of their excellent properties.2. Application of hyperchaos signals to encryption of active images is studied, a new method for encryption of active images utilizing更多还原