【作者】 赵永斌；

【导师】 胡予濮；

【作者基本信息】 西安电子科技大学 ， 密码学， 2014， 博士

【摘要】 流密码具有结构简洁、加密速度快、错误传播有限等特点,广泛用于高速数据传输与加密。基于硬件的流密码更因低功耗特性,在资源受限环境下发挥着无可替代的作用。本文对流密码的几类基本部件:线性反馈移位寄存器、非线性反馈移位寄存器和布尔函数进行了研究和分析,取得以下主要成果:(1)通过分析线性反馈移位寄存器延迟序列和初始状态间的关系,给出了能够完全抵抗能量攻击所需触发器数目的下界。提出了一种线性反馈移位寄存器设计方案,在抵抗线性反馈移位寄存器能量攻击时,附加触发器的个数至多为5个,有效降低了线性反馈移位寄存器的附加功耗。(2)针对基于非线性反馈移位寄存器和布尔函数的流密码算法,通过分析输出布尔函数和非线性反馈移位寄存器反馈函数的Walsh谱值,提出了一种基于Walsh谱的非线性部件的密码分析方法。在分析平衡性、非线性度、相关免疫度等密码学指标基础上,查找影响函数密码学性质的关键Walsh谱值点,对存在问题的谱值点进行函数值分析,判断算法是否符合安全性要求。最后利用该方法对流密码Grain v1进行了分析,通过Walsh谱分布指出了算法中存在的安全隐患。(3)重点研究了定义在2nZ上的4值广义Bent函数。给出了一种2nZ上4值Bent函数的构造方法,该方法主要用于生成奇数个变元的广义Bent函数。然后,通过布尔置换,给出了奇变元广义Bent函数的具体实现方法。(4)通过分析Bent函数的函数值和游程特性,提出了一种基于真值表的Bent函数搜索算法,与其他搜索算法相比,该方法具有较低的存储复杂度,易于使用并行计算实现等特点。更多还原

【Abstract】 Having advantages of simple structure and hardware, fast encryption speed and limited error propagation, stream cipher is widely used as an encryption in high-speed data transmission. Hardware-based stream ciphers are suitable for constrained environments because of its much lower power consumption than the other ciphers. This dissertation focuses on the primitive components of stream ciphers: linear feedback shift registers, nonlinear feedback shift registers and Boolean functions. The contributions of this dissertation are listed as follows.(1) By analyzing the relations between the delayed sequence and the initial states, the paper lower bounds the numbers of flip-flops in the design of LFSR-based stream ciphers resisting the power analysis attack. Besides, a novel lightweight design to resist power analysis attack is proposed. With this method, the number of flip-flops required is decreased to five and the power consumption is significantly reduced.(2) For stream ciphers combined by an NLFSR and a Boolean function, a new Walsh spectrum analysis method of nonlinear components is presented. This is achieved by analyzing the Walsh spectrum of the output Boolean function and NLFSR function. Besides the security properties of balancedness, nonlinearity and correlation immunity of nonlinear components, this paper also focuses on the key values of Walsh spectrum, which may influence these security indicators. With this method, the weakness of the nonlinear component can be found much easier. Finally, the work points out the security weakness of Grain v1.(3) The paper presents a construction of generalized bent Boolean functions defined on 2nZ with values in Z4. The main usage is to derive generalized bent functions on odd number of variables. In addition, by using Boolean permutations, we provide a specific method to construct generalized bent functions on odd number of variables.(4) Based on the analysis of the value and the run characteristics of the Bent function, we present an algorithm for searching the true value table of the Bent function. Comparing with the existing algorithms, the proposed algorithm has a lower storage complexity, and is easy to compute in parallel.更多还原