新型数据加密算法与高效连续相位调制的研究

发布时间：2018-03-27 17:45

本文选题：CPM　切入点：串行级联码　出处：《南京航空航天大学》2014年硕士论文

【摘要】：保密通信系统中的保密信息在传输过程中不仅会遭受人为窃取,还会受到噪声干扰。本文基于以上问题对保密通信系统进行研究。一方面为了保证系统的安全性,文中采用分组加密算法对保密模块进行设计,并用线性密码分析验证其安全性。另一方面为了增强系统的抗噪声干扰能力,可以使用信道编码技术。但同时信道编码技术增加了信息的冗余位,降低了系统的频谱利用率。本文提出将连续相位调制(Continuous Phase Modulation,CPM)与信道编码级联构成串行级联码进行迭代译码,不仅可以提高系统的频谱利用率,而且能够达到接近Turbo码的误码性能。本文的主要工作及研究成果概括如下:1、采用多轮迭代结构的分组密码算法进行密码器设计。通过对加密结构的核心部分——非线性S盒进行线性逼近,分析密码器的安全性。针对算法中原始密钥固定不变、长度短、抗攻击性弱的问题,利用Logistic混沌映射进行改进,生成了动态的初始密钥,有效扩展了密钥空间,增强了系统安全性。2、研究CPM的内在编码特性。将CPM的传统相位替换为倾斜相位,推导出Rimoldi分解模型,同时得到时不变的相位状态转移图。用基于状态网格图的Viterbi算法对CPM中的MSK信号进行最大似然检测,并针对算法中相位路径选择造成的延时问题进行分析改进。仿真结果验证了Rimoldi分解模型的有效性,证明了CPM调制具有编码增益,可等效为编码器进行研究。3、针对保密通信系统中的噪声干扰,提出将CPM应用于串行级联码,构成串行级联CPM。推导了适用于CPM检测器的最大后验概率(Maximum A Posteriori,MAP)迭代译码算法,并通过分析修改相位分支度量,降低了运算复杂度。通过仿真,验证了串行级联CPM通过伪随机交织器进行迭代译码能够明显提高系统的可靠性。
[Abstract]:The confidential information in the secure communication system will not only be stolen by human beings, but also be disturbed by noise during the transmission. This paper studies the secure communication system based on the above problems. On the one hand, in order to ensure the security of the system, In this paper, the block encryption algorithm is used to design the security module, and the linear cipher analysis is used to verify its security. On the other hand, in order to enhance the anti-noise ability of the system, The channel coding technique can be used, but at the same time, the channel coding technique increases the redundant bits of information and reduces the spectrum efficiency of the system. In this paper, a serial concatenated code is constructed by cascading continuous phase modulation (CPM) and channel coding to perform iterative decoding. Not only can the spectrum efficiency of the system be improved, The main work and research results of this paper are summarized as follows: 1. The block cipher algorithm with multi-round iterative structure is used to design the cipher. Linear S-box for linear approximation, This paper analyzes the security of cryptographer. Aiming at the problems of the original key fixed, short length and weak attack resistance in the algorithm, the Logistic chaotic mapping is used to improve the algorithm, and the dynamic initial key is generated, which effectively expands the key space. The system security. 2 is enhanced, and the inherent coding characteristics of CPM are studied. The traditional phase of CPM is replaced by tilted phase, and the Rimoldi decomposition model is derived. At the same time, the phase state transition diagram of time invariant is obtained. The maximum likelihood detection of MSK signal in CPM is carried out by using the Viterbi algorithm based on state grid graph. The simulation results show the validity of the Rimoldi decomposition model and the coding gain of CPM modulation. For the noise interference in the secure communication system, a serial concatenated code is constructed by applying CPM to the serial concatenated code. The maximum posterior probability Maximum A Posteriori map iterative decoding algorithm is derived for the CPM detector. By analyzing and modifying the phase branching metric, the computational complexity is reduced, and the simulation results show that the serial concatenated CPM can improve the reliability of the system obviously by using pseudorandom Interleaver to perform iterative decoding.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN918.4;TN911.3

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