蓝牙组合生成器相关系数的计算方法

蓝牙组合生成器是蓝牙协议中使用的密钥流生成算法,它是一个带4 bit记忆的非线性组合生成器,其输入和输出之间相关系数的表示和计算是一个困难的问题,而这是对这种生成器进行相关性分析和相关攻击的基础.该文对一般的带记忆组合生成器给出了相关系数和条件相关系数的计算公式,该公式易于实现快速计算.基于此公式计算了蓝牙组合生成器的各种相关系数,并列出了部分结果.     

一类钟控组合生成器的符合率

给出3个停走生成器在模2加组合方式下符合率的有关结论。此类生成器的输出序列与相应停走生成器的控制序列相互独立;输出序列与相应停走生成器的目标LFSR输出序列不独立,本文对输出序列与目标LFSR序列的符合率进行了讨论,给出有限维联合分布的计算公式。     

滤波生成器的旋转对称攻击

滤波生成器的安全性主要由滤波函数提供.为抵抗代数攻击,通常选取代数免疫函数作为滤波函数.我们发现已知的几类代数免疫函数都具有较强的旋转对称性,并在此基础上给出了一种针对滤波函数的旋转对称性质的攻击方法.我们还讨论了布尔函数的旋转对称性质以及该性质对旋转对称攻击的影响,分析了最优代数免疫函数对旋转对称攻击的脆弱性,提出了...     

联合的F-FCSR密钥流生成器

 在分析带进位反馈移位寄存器(FCSR)的滤波密钥流生成器族F-FCSR线性弱点和其硬件方案F-FCSR-Hv2被攻破原因基础之上,提出了利用两个F-FCSR输出简单非线性运算而成的联合的F-FCSR密钥流生成器.该生成器避免了利用该种情况而进行的Hell-Johansson攻击,其生成序列通过了美国技术与标准局(NIST)STS的16项随机性测试,有高的复杂度,且能抵抗相关攻击和代数攻击.     

带记忆多值组合生成器的相关免疫性

考察带l位记忆多值组合生成器输入序列和输出序列的相关免疫性以及k阶相关免疫组合函数的构造。     

对一类过滤生成器的攻击

为了对过滤生成器实施攻击,提出一种求解概率方程组的算法,此算法利用系数矩阵的逆矩阵选取概率方程组的解;然后分析一类支撑集具有特殊结构的过滤函数,得到一条间断序列,再结合求解概率方程组的算法对过滤生成器实施攻击.分析结论可知,得到的攻击方法具有较好的灵活性和可行性.     

一类密钥流生成器的相关分析

多输出逻辑函数是构造密码系统的重要工具,相关免疫性是设计安全逻辑函数的重要准则。该文利用一种较为简单的方法证明了多输出逻辑函数相关免疫性两种刻划的等价性。还对一类利用多输出逻辑函数相关免疫函数构造的密钥流生成器进行了相关性分析,证明了这种构造方法是不成立的,并不能达到构造者期望的相关免疫性,并且分别利用Walsh变换技术和线性序列电路逼近方法找出了这类密钥流生成器的漏洞,从而说明这类生成器在相关攻击下是脆弱的。     

全动态密钥流生成器DF-FCSR-8

研究了基于带进位的反馈移位寄存器(FCSR)滤波的密钥流生成器族(F-FCSR),在分析F-FCSR线性弱点和F-FCSR-Hv2被攻破原因的基础之上,提出了全动态滤波密钥流生成器DF-FCSR-8。避免了利用该种情况而进行的Hell-Johansson攻击。其生成序列通过了美国技术与标准局(NIST)STS软件包的16项随机性测试,有良好的随机性。同时生成器也能抵抗其他攻击。     

基于FCSR的双滤波密钥流生成器

当前,由于还没有一个适于一般目的的流密码国际加密标准,流密码的设计与分析引起了广泛关注。在以前的流密码的设计中多采用线性反馈移位寄存器（LFSR）作为基本的部件。然而由于LFSR本身的线性性,基于LFSR的流密码备受攻击,进而相继出现了一些替换部件,例如T函数,带进位的反馈移位寄存器（FCSR）等等。文中给出了一个新的基于FCSR的密钥流生成器。理论分析表明该密钥流生成器具有高度的安全性。NIST统计测试表明该密钥流生成器的伪随机特性是理想的。     

Fast Correlation Attacks on the Summation Generator

The linear sequential circuit approximation method for combiners with memory is used to find mutually correlated linear transforms of the input and output sequences in the well-known summation generator with any number of inputs. It is shown that the determined correlation coefficient is large enough for applying a fast correlation attack to the output sequence to reconstruct the initial states of the input linear feedback shift registers. The proposed attack is based on iterative probabilistic decoding and appropriately generated low-weight parity-checks. The required output sequence length and the computational complexity are both derived. Successful experimental results for the summation generators with three and five inputs are obtained. Received 13 December 1996 and revised 7 October 1998     

Correlation properties of a general binary combiner with memory

Correlation properties of a general binary combiner with an arbitrary number M of memory bits are derived and novel design criteria proposed. For any positive integer m, the sum of the squares of the correlation coefficients between all nonzero linear functions of m successive output bits and all linear functions of the corresponding m successive inputs is shown to be dependent upon a particular combiner, unlike the memoryless combiners. The minimum and maximum values of the correlation sum as well as the necessary and sufficient conditions for them to be achieved are determined. It turns out that the security of combiners with memory can be considerably improved if M is not small.An efficient linear sequential circuit approximation (LSCA) method is developed for obtaining output and input linear functions with comparatively large correlation coefficients which is feasible for large M and works for any practical scheme. The method consists in deriving and solving a linear sequential circuit with additional nonbalanced inputs that is based on linear approximations of the output and the component next-state functions. The corresponding correlation attack on combiners with linear feedback shift registers is analyzed and it is shown that every such combiner with or without memory is essentially zero-order correlation immune.A preliminary version of this paper was presented at Eurocrypt '92 and was published in the proceedings. This research was supported in part by the Science Fund of Serbia, Grant #0403, through the Institute of Mathematics, Serbian Academy of Arts and Sciences.     

Conditional correlation attack on combiners with memory

A connection between linear codes and the correlation attack conditioned on the output of binary combiners with memory is established. Using a sort of random coding argument, it is shown that an average combiner with memory is potentially vulnerable to such an attack only if the number of outputs is equal to or greater than the number of inputs. The required computational complexity in the former case is exponentially greater than in the latter case     

Optimal diversity combining under correlated noise in mobile radio

In this paper the performance of predetection maximal ratio and equal gain combiners are investigated under conditions of correlated branch noise. A statistical model is devised to determine the spatial noise correlation coefficients at metropolitan‐area base stations, and the cases where significant correlation is likely are clarified. Optimal weighting coefficients for a maximal ratio combiner with two‐branch space diversity are derived under correlated noise. Based on this result it is shown that correlation in branch noise can be used to improve the combiner performance by dynamically adjusting the weightings so as to partially cancel the noise. Performance of equal gain combiners is also shortly discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Multi-step attack detection method based on network communication anomaly recognition

In view of the characteristics of internal fixed business logic,inbound and outbound network access behavior,two classes and four kinds of abnormal behaviors were defined firstly,and then a multi-step attack detection method was proposed based on network communication anomaly recognition.For abnormal sub-graphs and abnormal communication edges detection,graph-based anomaly analysis and wavelet analysis method were respectively proposed to identify abnormal behaviors in network communication,and detect multi-step attacks through anomaly correlation analysis.Experiments are carried out on the DARPA 2000 data set and LANL data set to verify the results.The experimental results show that the proposed method can effectively detect and reconstruct multi-step attack scenarios.The proposed method can effectively monitor multi-step attacks including unknown feature types.It provides a feasible idea for detecting complex multi-step attack patterns such as APT.And the network communication graph greatly reduces the data size,it is suitable for large-scale enterprise network environments.     

Harmonic Power Combining Of Microwave Solid-State Active Devices

A method for combining the power in a selected harmonic of the fundamental frequency for a symmetrical array of oscillating solid-state devices is described and demonstrated. These combiners convert fundamental power to harmonic power with filtering accomplished by symmetry. This technique appears useful for improving the performance of microwave and millimeter-wave power sources by effectively enhancing the frequency-power limitations of existing solid-state devices. An example of the method is provided by a simple three-phase frequency-tripling varactor-tuned transistor oscillator.     

线性反馈移位寄存器的差分能量攻击

能否有效去除算法噪声的影响,直接关系到能量攻击成败。该文以线性反馈移位寄存器(LFSR)相邻两个时钟周期的能量消耗差异为出发点,提出了一种新的差分能量攻击算法。它从根本上去除了密码算法噪声在攻击过程中带来的影响。由于该算法随机选择初始向量(initialization vector),从而使攻击者能够容易地将其推广到具有类似结构的流密码体制。为了进一步验证攻击算法的有效性,该文利用软件仿真的方法对DECIM进行了模拟攻击。仿真结果表明,该攻击算法能够有效降低LFSR的密钥搜索的复杂度。