共查询到19条相似文献,搜索用时 187 毫秒
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提出了用于分组密码分析的分区线性分析法.以SAFER++为例,通过基础模块的密码特性分析,建立密码分析的线性逼近式.该逼近式的特点是把密钥的比特位分区出现在逼近式的任选项中,这样不仅可以攻击密钥的所有比特位,而且大大降低了攻击的复杂度,并从理论上证明了逼近式的优势与任何子密钥的最低有效位无关.迄今为止有关文献都认为相关子密钥最低有效位等于0是逼近优势非零的前提条件. 相似文献
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SAFER-64的弱密钥 总被引:1,自引:1,他引:0
侯宇 《中国计量学院学报》2007,18(1):54-58
通过对SARER-64系统基础模块的深入分析,构建了由6个线性逼近式组成的循环逼近式系统.由于循环性,该逼近式系统可以用来对任意轮次的SARER-64进行多重线性密码分析,从而确定系统的弱密钥.现以五轮SARER-64为例,构建多重线性逼近式并分析系统的弱密钥. 相似文献
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在混合差分法基础上研究SARER-64系统密码分析的加速技术.建立了明文对选择策略,给出了限定字节密钥范围算法和错误密钥的快速剔除法.结果表明,运用加速技术可大大地加快密码分析速度. 相似文献
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分析了RSA和DES的算法优点和安全弱点,设计了一个新的密码算法方案。该方案以类FEISTEL结构为基础增强了左右两半部分结构的安全设计,利用了RSA进行密钥分配,并以序列密码算法的生成原理改变了固定密钥的缺点。该新方案具有一次一密的特点,给破译者获得大量的明密文对造成了很大的困难,可较好地抵抗差分分析与线性分析,是一种安全性较强的加密方案。 相似文献
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重点研究由CdO-SnO2-WO3系列(以下简称Cd-Sn-W)和CdO-Sb2O3-WO3系列(以下简称Cd-Sb-W)及由它们共同组成的双基体三相(Cd2Sb2O7、CdSnO3、CdWO4)结构线性敏感陶瓷的制备方法.给出了上述半导体陶瓷的电子转移式;分析了半导相Cd2Sb2O7和CdSnO3的导电机理和电阻-温度(R-T)曲线呈线性的机理.并对其他相关特性进行了深入的分析和研究. 相似文献
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网络即时通讯在为人们日常交流带来便利的同时,也伴随着信息泄露、个人隐私被窃等烦扰。如何保证敏感信息在网络上安全的传输成为一个重要的研究课题。基于网络通信的软件都需要采用加密手段来最大限度上对用户的敏感信息进行保护,其中密钥的管理将影响整个系统的性能和安全性。模拟SSL协议原理,提出使用公钥密码进行私密钥的分配,并通过密钥分配中心(KDC)对公钥密码进行认证的解决方案。 相似文献
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高级像差对人眼成像质量和视觉的影响 总被引:3,自引:0,他引:3
定量地研究高级像差对人眼成像质量和视觉的影响对人眼像差矫正具有重要的实验和临床意义.利用Hartmann-Shack波前传感器人眼像差仪测量了正常人眼6mm瞳孔的波前像差,由波前像差计算出人眼光学系统的光学调制传递函数MTF和Strehl比率,并由MTF和视网膜空间像调制度AIM曲线计算出人眼视锐度和对比敏感度函数CSF.根据MTF和Strehl比率分析了高级像差对人眼成像质量的影响,根据视锐度和对比敏感度函数CSF分析了高级波像差对视觉的影响.研究表明Zernik前6级像差对人眼成像质量和视觉的影响是不可忽略的,更高级的像差对人眼成像质量和视觉的影响较小,甚至可以忽略.对Zemik前6级像差进行矫正,可以得到相当好的视觉. 相似文献
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考虑轴的自重的影响,研究轴的质量中心分布线与旋转中心线不重合时的扭/弯耦合振动情况。研究中,基于轴的基本理论建立了轴的扭/弯耦合振动的方程组,并根据振型叠加法以及模态的正交性进行了耦合方程组的求解。对简支轴仅考虑自重情况下轴的扭/弯耦合振动进行了自由振动和强迫振动的研究,对与理论研究条件相同的实际简支轴进行了耦合振动响应的实测研究。研究结果表明:第一、三、五…阶弯曲振动是跟第二、四、六…阶扭转振动相耦合的,而第二、四、六…阶弯曲振动则是跟第一、三、五…阶扭转振动相耦合。 相似文献
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Kim Y 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(12):1683-1688
Amplitude-frequency effect of a Y-cut langanite (LGN) resonator and a Y-cut langatate (LGT) resonator were measured. The frequency shifts from the baseline frequency with 1 mA were measured as a function of drive currents up to 28 mA. High-drive current shifted the frequency, but it also heated the crystal locally, causing temperature-related frequency changes. The local heat transfer and its influence on the frequency were analyzed. The amplitude-frequency shift was effectively measured, and was not affected by the temperature-related frequency changes. The 3rd, 5th, and 7th overtones (OT's) were found to behave as soft springs, i.e., resonant frequency decreases as drive current increases. The drive sensitivity coefficients of the 3rd and 5th OT's are in the vicinity of -2 ppb/mA/sup 2/ for both resonators. The 7th OT's are higher than the other OT's: -5/spl sim/- 7 ppb/mA/sup 2/. The lowest drive sensitivity is -1.2 ppb/mA/sup 2/ on the 5th OT of the LGT. 相似文献
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The generalized stacking fault (GSF) energies and surface energies of magnesium and its alloys with alloying atoms X- C, B, N, O and vacancy have been investigated using the first-principles methods. It is found that the predominant reducing effects of the alloying atoms and vacancy on the stacking fault energy are resulted from the position of them in the 1st layer near the slip plane. The stacking fault energies are nearly the same as the pure magnesium while the alloying atoms and vacancy are placed in the 2nd, 3rd, 4th, 5th and 6th layers. It has been shown that O strongly reduces the GSF energy of Mg. The alloying atoms C, B and N increase the surface energy, but O and vacancy reduce the surface energy of Mg. The ductilities of Mg and Mg alloys have been discussed based on the Rice criterion by using the ratio between surface energy and unstable stacking fault energy. 相似文献
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介绍了核电堆型发展的四个阶段和第一、二代核电堆型的发展历史;论述了第三代先进堆型的发展、设计特点和第四代先进堆的开发目标 相似文献
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介绍了一种新型的ATM-PON系统,它采用在PON传输层上定义ATME层的方法取代传统的ATM层,并采用包含6byte信头的双向54byte信元格式,可获得较高的传输容量。在VP级上控制上行信号的发送和管理连接资源,可实现灵活的动态带宽分配。 相似文献
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E. Dul'kin 《Journal of Superconductivity and Novel Magnetism》2003,16(6):953-956
YBa2Cu3O7?X ceramic samples voltage–current characteristics at 77 K and acoustic emission activity during thermocycling 500–600 K region have been studied. Partial oxygen sorption by these samples through heating has been established by critical-current value and acoustic emission activity at 540–550 K. During thermocycling an acoustic emission maximums have been observed on 3rd and 6th thermocycles, and these maximums correlate with some decrease of the critical-current value. It is shown that observed acoustic emission maximums are because of a phase-work hardening during thermocycling of these samples. A mechanism of this phase-work hardening influencing the critical-current value in YBa2Cu3O7?X ceramic samples is discussed. 相似文献
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《Composites Part A》2002,33(5):725-734
The aim of this paper is to describe a model for the prediction of the formability of a multiaxial warp knitted (MWK) fabric to a 3D surface. For this purpose, we first characterized in detail the forming behavior of MWK fabrics containing two bias inserting yarns (TBMWK fabric). Through experimental observation, it was found that the two bias inserting yarns always tend to gather along the weft direction. The angle between the two bias yarns has a linear relationship with the perpendicular distance from the measured points to the longitudinal axis of the hemisphere during forming process. The slope of this linear relationship is also linear with the magnitude of radius of the pressing hemisphere provided that the radius is larger than 7 cm.Based on the above finding, a mathematical model is established for predicting the deformations of TBMWK fabrics during the hemisphere-forming process. The shape of flat TBMWK fabric that can yield the corresponding hemisphere during the forming process as well as local deformations can be calculated through this model. The hemisphere-forming experiments show that the present model is workable and accurate. The results from both the model and experiments suggest that the shape of flat TBMWK fabric that can yield the corresponding hemisphere which is close to a rectangular, not to a square as presented by woven fabric.The method developed in the paper has laid a foundation for further modeling of the forming behavior of MWK fabrics onto other 3D surfaces. More importantly, it is of great value to find that the two bias inserting yarns always tend to gather along the weft direction of the fabric which is a starting point for modeling of the forming behavior of MWK fabrics. 相似文献