分组密码的分析与设计

分组密码作为现代密码学的一个重要组成部分，是目前最重要和流行的一种数据加密技术，有着非常广泛的应用。此外，近年来分组密码或其组件还经常作为基础模块用于构造Hash函数，MAC算法等。因此对分组密码安全性的分析以及设计安全高效的分组密码算法，在理论研究及实际应用中都有着非常重要的意义。本文的研究内容主要包括两个方面：对现有常用分组密码的安全性分析，以及分组密码及其组件的设计。这两个方面是密不可分，相互融合的。通常都是利用算法存在的弱点或算法设计特点，提出新的密码分析算法。而在算法设计过程中，正是从密码分析获取经验，掌握设计算法的技巧和避免可能存在的缺陷。 本文首先对分组密码分析方法作了大量的调查和研究，在此基础上分析了一些国内外常用和有影响的分组密码，得到了一系列有价值的分析结果。并在密码分析工作的经验基础上，结合现有密码设计理论，在分组密码及其组件的设计方面做了比较深入的研究。本文的主要成果包括： (1) DES算法的分析。DES算法是迄今最重要的分组密码算法之一，目前在一些金融领域，DES和Triple-DES仍被广泛使用着。本文考察了DES算法针对Boomerang攻击和Rectangle攻击的安全性。通过利用DES算法各轮的最优差分路径及其概率，分别给出了这两种攻击方法对DES的攻击算法。 (2) Rijndael算法的分析。Rijndael算法是高级加密标准AES的原型。本文针对大分组Rijndael算法的各个不同版本，利用算法行移位和列混淆变换的一些密码特性，改进了原有的不可能差分攻击结果，极大的降低了攻击的数据和时间复杂度。同时还分别构造了一些新的更长轮的不可能差分路径，利用这些路径给出了一系列对大分组Rijndael算法的改进的不可能差分攻击，这些结果是目前已知的对该算法的最好攻击结果。 (3) SMS4算法的分析。SMS4算法是中国公布的用于无线局域网产品保护的算法。本文首先构造了SMS4算法的一类5轮循环差分特征，利用该特征分别给出了对16轮SMS4算法的矩阵攻击和对21轮SMS4算法的差分分析。随后考察了SMS4算法抵抗差分故障攻击的能力，基于字节故障模型，结合实验指出需要32次故障诱导来恢复全部密钥。后续的工作又进一步将结果改进为只需要进行一次故障诱导再结合2^{44}次密钥搜索即可恢复全部密钥。 (4) CLEFIA密码算法的分析。CLEFIA算法是索尼公司于2007年提出的用于产品版权保护和认证的分组密码算法。针对CLEFIA算法，本文构造了一条概率为1的5轮截断差分特征，再结合其扩散矩阵的密码特性构造了一条3轮线性逼近。随后利用这两条路径组成的8轮差分-线性区分器，给出了对10轮CLEFIA算法的有效的差分-线性攻击。 (5) 分组密码结构的设计及其应用。本文提出了两种新的分组密码结构，并指出了其与原有结构相比的优势，同时分别评估了这两种结构针对差分分析和线性分析等常用密码分析方法的安全性。基于这两个密码结构，结合部分密码组件的设计和测试工作，本文还完成了两个分组密码算法的概要设计，并简要评估了它们的实现效率及针对现有的几种主要密码分析方法的安全性。

迷宫流道转角对灌水器水力性能的影响

为研究齿形、梯形以及矩形流道转角变化对水力性能的影响,采用Fluent软件对不同形状下不同转角的流道进行了数值模拟。研究结果表明:当其他条件相同时,转角的变化与流量系数、流态指数呈负相关,其变化对梯形流道灌水器的流量系数影响最大,最多下降了19.03%,齿形流道次之,下降了10.14%,矩形流道是梯形流道转角角度增加的延伸,具有相同的水力性能变化规律;随着角度的增加,梯形流道总的局部水头损失系数最多增加了32.5%,而齿形流道总的局部水头损失系数最多增加了23.4%,变化都很明显;压力较高时,摩阻系数基本保持不变,流体为紊流状态。

The effect of human rhythm on packet delivery

In communication networks such as the Internet, the relationship between packet generation rate and time is similar to a rectangle wavefunction due to the rhythm of humans. Thus, we investigate the traffic dynamics on a network with a rectangle wavepacket generation rate. It is found that the critical delivering capacity parameter beta(c) (which separates the congested phase and the free phase) decreases significantly with the duty cycle r of the rectangle wave for package generation. And, in the congested phase, more collective generation of packets (smaller r) is helpful for decreasing the packet aggregation rate. Moreover, it is found that the congested phase can be divided into two regions, i.e., region1 and region2, where the distributions of queue lengths are nonlinear and linear, respectively. Also, the linear expression for the distribution of queue lengths in region2 is obtained analytically. Our work reveals an obvious effect of the rectangle wave on the traffic dynamics and the queue length distribution in the system, which is of essential interest and may provide insights into the designing of work-rest schedules and routing strategies.

八单元一维位置灵敏雪崩室

In the experiment of nuclear reaction, it is important to measure the mass, charge, energy and emitted direction of particles. For multiparameter measurement, we must use a detector or a group of detectors which can give the time, energy, and position information. The Large Area position sensitive Ionization Chamber(LAIC) is one of the eight experiment terminals of HIRFL. It is built for researching nuclear reactions from low energy to intermediate energy. It is an excellent equipment for energy measurements and atomic number identification of emitted fragments in this energy region. It is also designed to give the time and position information of the emitted fragments by itself. Obviously, an IC can not supply a good timing signal. Moreover, the mechanical installation is different from the original design by some other reasons. In this case, it is not enough to obtain the correct direction information of the emitted fragments. To obtain good timing signals and the correct direction information, some modifications must be made. It is well known that a PPAC can give us excellent timing signals. It also can be easily built as a position sensitive detector. For this reason, a specially designed PPAC is installed in the entrance of the LAIC. For the different purposes, two types of PPACs were designed and tested. Both are OCTPSACs (OCTunit one dimension Position Sensitive Avalanche Counter). In this paper, both OCTPSACs will be introduced. Based on the requirements of the LAIC, the OCTPSACs consist of eight position sensitive PPACs. Each PPAC has an anode and a cathode. In both cases, the sizes are same. But different type of cathodes are used. In one type of OCTPSAC, its cathode is made of wire plane. It consists of gold-plated tungsten wires with the diameter of 20μm, spaced 0.5 mm apart from each other. The anode is a mylar foil which was evaporated by gold layer with the thickness of 50μg/cm~2 mounted on a printed plate in the shape of rectangle. the thickness of mylar foil is 1.5μm. The gap between anode and cathode is 3mm. The performance of the OCTPSAC has been tested by using a ~(252)Cf source in flowing isobutylene gas at the pressure of 3.4mb. The intrinsic time resolution of 289ps and position resolution of 2 mm have been obtained. In another type of OCTPSAC, the cathode is made of mylar foil, which is composed of gold strip by vacuume evaporation method with a special mask on the mylar foil. The thickness and the width of the gold strip is 50μg/cm~2 and 1.7mm. The strips are spaced 0.3 mm apart from each other. The anode is the same as the former type. We have obtained the time resolution of 296ps and position resolution of 2mm by using ~(241)Am-a source when the gas pressure is 6 mb and high voltage is 600V. The working gas is heptane

Phase transition of BaNd2Mn2O7

Phase transition of BaNd2Mn2O7 from orthorhombic (space group Fmmm) to tetragonal phase (I4/mmm) was studied by high temperature powder X-ray diffractometry and Rietveld analysis. The transition temperature was identified at 523 K, which is almost the same transition temperature as the compounds with other rare earth ions in this BaLn(2)Mn(2)O(7) family (Ln=Sm and Eu) with Fmmm space group. During the transition an oxygen octahedron of each phase changes a little its form, in which four oxygen atoms perpendicular to C-axis make a rectangle and a square for orthorhombic and tetragonal phases, respectively. Manganese ion is not on the center of the quadrilateral consisting of these four oxygen ions, but a little apart from the center along c-axis in both phases.

Trichodinid ectoparasites (Ciliophora, Peritrichia) from the tiger puffer Takifugu rubripes in the Yellow Sea, with revision of Trichodina jadranica Raabe,1958

Two ectoparasitic ciliates, Trichodina fugu Imai et al., 1997 and T. jadranica Raabe, 1958, found on the gills and skin of the maricultured tiger puffer Takifugu rubripes on the China coast of the Yellow Sea, were studied using the dry silver nitrate method. Trichodina fugu is distinguished by its almost rod-shaped denticle blades. Trichodina jadranica is usually described as a small trichodinid with a clear central circle in the adhesive disc and with a low number of denticles. However, the data available suggest that the species is highly variable in morphometry and the Chinese population represents the largest in body size and denticle dimensions found to date. Based on the revision of T. jadranica, two major morphotypes, each represented by several populations are classified, differing in the shape of the blades, viz., distinctly curved and sickle-shaped with pointed distal ends (as in the classical T. jadranica) vs. less curved and more or less rectangle-like with rounded distal ends (as in T. domerguei gobii). Trichodina domerguei gobii Raabe,.1959, which was synonymised with T. jadranica, is thus elevated to species rank. Furthermore, Trichodina jadranica noblei Lom, 1970 has straight and stout blades with broadly rounded distal ends and is raised to species rank: T noblei Lom, 1970. Trichodina jadranica sensu Xu et al., 1995 shows high similarities in denticle shape and dimensions as well as the central granule pattern with T chlamydis Xu et al., 1999. Thus, it is synonymised with the latter species.

基于水下作业系统阻抗力控制水下目标定位

提出了基于水下作业系统阻抗力控制的水下矩形围壁定位方法。水下作业系统末端执行器跟踪期望运动轨迹,通过与水下矩形围壁环境表面接触力反馈信息的变化获得与环境接触的特殊点,计算得到矩形围壁环境相对水下作业系统的位姿。以带有三自由度机械手的水下作业系统为例进行水下矩形围壁目标表面恒力跟踪的计算机仿真,仿真结果表明定位方法可以很好的获得矩形围壁环境的位姿,控制策略具有很好的表面跟踪和力控制能力。

各向同性与各向异性介质中地震波旅行时正演模拟与反演成像

By seismic tomography, interesting results have been achieved not only in the research of the geosphere with a large scale but also in the exploration of resources and projects with a small scale since 80'. Compared with traditional inversion methods, seismic tomography can offer more and detailed information about subsurface and has been being paid attention by more and more geophysicists. Since inversion based on forward modeling, we have studied and improved the methods to calculate seismic traveltimes and raypaths in isotropic and anisotropic media, and applied the improved forward methods to traveltime tomography. There are three main kinds of methods to calculate seismic traveltime field and its ray path distribution, which are ray-tracing theory, eikonal equation by the finite-difference and minimum traveltime tree algorithm. In ray tracing, five methods are introduced in the paper, including analytic ray tracing, ray shooting, ray bending, grid ray tracing and rectangle grid ray perturbation with three points. Finite-difference solution of eikonal equation is very efficient in calculation of seismic first-break, but is awkward in calculation of reflection traveltimes. We have put forward a idea to calculate traveltimes of reflected waves using a combining way of eikonal equation method and other one in order to improve its capability of dealing with reflection waves. The minimum traveltime tree algorithm has been studied with emphases. Three improved algorithms are put forward on the basis of basic algorithm of the minimum traveltime tree. The first improved algorithm is called raypath tracing backward minimum traveltime algorithm, in which not only wavelets from the current source but also wavelets from upper source points are all calculated. The algorithm can obviously improve the speed of calculating traveltimes and raypaths in layered or blocked homogeneous media and keep good accuracy. The second improved algorithm is raypath key point minimum traveltime algorithm in which traveltimes and raypaths are calculated with a view of key points of raypaths (key points of raypths mean the pivotal points which determine raypaths). The raypath key point method is developed on the basis of the first improved algorithm, and has better applicability. For example, it is very efficient even for inhomogeneous media. Another improved algorithm, double grid minimum traveltime tree algorithm, bases upon raypath key point scheme, in which a model is divided with two kinds of grids so that the unnecessary calculation can be left out. Violent undulation of curved interface often results in the phenomenon that there are no reflection points on some parts of interfaces where there should be. One efficacious scheme that curved interfaces are divided into segments, and these segments are treated respectively is presented to solve the problem. In addition, the approximation to interfaces with discrete grids leads to large errors in calculation of traveltimes and raypaths. Noting the point, we have thought a new method to remove the negative effect of mesh and to improve calculation accuracy by correcting the traveltimes with a little of additional calculation, and obtained better results.

Mieszanie stanów magnetycznych w skończonych układach spinowych opisywanych modelem Heisenberga

Wydział Fizyki: Zakład Fizyki Komputerowej

RECTANGLES MAY APPEAR TO REVERSE LIKE TRAPEZIA WHEN THEY ROTATE AT AN UNEVEN RATE

A 1983-1985 theory by Mitchell and Power predicts that, when rotating rectangles undergo certain kinds of speed fluctuation, they should appear to reverse just as trapezia do. The prediction is partially confirmed. One of two 'mimic' rectangles underwent apparent reversals more often than a control rectangle undergoing even rotation and in the same places as rotating trapezia. However, its reversal frequency was less than those of the trapezia, and a second 'mimic' showed an inappropriate distribution of reversals round the cycle. These anomalies call for some modification to Mitchell and Power's theory, but minor qualifications may be sufficient.

Epitaxial growth of non-c-oriented ferroelectric SrBi2Ta2O9 thin films on Si(100) substrates

Epitaxial SrBi2Ta2O9 (SBT) thin films with well-defined (116) orientation have been grown by pulsed laser deposition on Si(100) substrates covered with an yttria-stabilized ZrO2 (YSZ) buffer layer and an epitaxial layer of electrically conductive SrRuO3. Studies on the in-plane crystallographic relations between SrRuO3 and YSZ revealed a rectangle-on-cube epitaxy with respect to the substrate. X-ray diffraction pole figure measurements revealed well defined orientation relations, viz. SBT(116)\\ SrRuO3(110)\\ YSZ(100)\\ Si(100), SBT[110]\\ SrRuO3[001], and SrRuO3[111]\\ YSZ[110]\\ Si[110].

New FMO Type to Flag ROI in H264/AVC

This paper presents a new type of Flexible Macroblock Ordering (FMO) type for the H.264 Advanced Video Coding (AVC) standard, which can more efficiently flag the position and shape of regions of interest (ROIs) in each frame. In H.264/AVC, 7 types of FMO have been defined, all of which are designed for error resilience. Most previous work related to ROI processing has adopted Type-2 (foreground & background), or Type-6 (explicit), to flag the position and shape of the ROI. However, only rectangular shapes are allowed in Type-2 and for non-rectangular shapes, the non-ROI macroblocks may be wrongly flagged as being within the ROI, which could seriously affect subsequent processing of the ROI. In Type-6, each macroblock in a frame uses fixed-length bits to indicate to its slice group. In general, each ROI is assigned to one slice group identity. Although this FMO type can more accurately flag the position and shape of the ROI, it incurs a significant bitrate overhead. The proposed new FMO type uses the smallest rectangle that covers the ROI to indicate its position and a spiral binary mask is employed within the rectangle to indicate the shape of the ROI. This technique can accurately flag the ROI and provide significantly savings in the bitrate overhead. Compared with Type-6, an 80% to 90% reduction in the bitrate overhead can be obtained while achieving the same accuracy.

Signal Reliability Improvement Using Selection Combining Based Macro-Diversity for Off-Body Communications At 868 MHz

This paper investigates the potential improvement in signal reliability for outdoor short-range off-body communications channels at 868 MHz using the macro-diversity offered by multiple co-located base stations. In this study, ten identical hypothetical base stations were positioned equidistantly around the perimeter of a rectangle of length 6.67 m and width 3.3 m. A body worn node was placed on the central chest region of an adult male. Five scenarios, each considering different user trajectories, were then analyzed to test the efficacy of using macro-diversity when the desired link is subject to shadowing caused by the human body. A number of selection combining based macro-diversity configurations consisting of four and then ten base stations were considered. It was found that using a macro-diversity system consisting of four base stations (or equivalently signal branches), a maximum diversity gain of 22.5 dB could be obtained while implementing a 10-base station setup this figure could be improved to 25.2 dB.

A aprendizagem da trigonometria do triângulo rectângulo através da resolução de problemas

Relatório da prática de ensino supervisionada, Mestrado em Ensino da Matemática, Universidade de Lisboa, 2010

Conhecimento dos alunos sobre geometria no início do 3.º ciclo

Dissertação apresentada para obtenção do grau de Mestre em Educação Matemática na Educação Pré-Escolar e nos 1.º e 2.º Ciclos do Ensino Básico