A genetic tango attack against the David–Prasad RFID ultra‐lightweight authentication protocol

Radio frequency identification (RFID) is a powerful technology that enables wireless information storage and control in an economical way. These properties have generated a wide range of applications in different areas. Due to economic and technological constrains, RFID devices are seriously limited, having small or even tiny computational capabilities. This issue is particularly challenging from the security point of view. Security protocols in RFID environments have to deal with strong computational limitations, and classical protocols cannot be used in this context. There have been several attempts to overcome these limitations in the form of new lightweight security protocols designed to be used in very constrained (sometimes called ultra‐lightweight) RFID environments. One of these proposals is the David–Prasad ultra‐lightweight authentication protocol. This protocol was successfully attacked using a cryptanalysis technique named Tango attack. The capacity of the attack depends on a set of boolean approximations. In this paper, we present an enhanced version of the Tango attack, named Genetic Tango attack, that uses Genetic Programming to design those approximations, easing the generation of automatic cryptanalysis and improving its power compared to a manually designed attack. Experimental results are given to illustrate the effectiveness of this new attack.     

Preparation and self‐assembly of poly(diglycidyl maleate‐co‐stearyl methacrylate)

Poly(diglycidyl maleate‐co‐stearyl methacrylate) (P(DGMA‐co‐SMA)) with reactive epoxy groups was synthesized by reaction of poly(maleic anhydride‐co‐stearyl methacrylate) (P(MA‐co‐SMA)) and epichlorohydrin. The effect of precipitant on self‐assembly behaviors of the resultant copolymer was investigated. It was found that vesicles and nanotubule liked aggregates can be obtained through self‐assembly of P(DGMA‐co‐SMA) in THF solution using CH₃CH₂OH (EtOH) as precipitant while spheral aggregates can be obtained using H₂O as precipitant. The mechanism of the self‐assembly behavior was discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

1，3－取代方酸衍生物的光谱研究及二聚体、簇集体的形成

本文合成了１，３－取代方酸衍生物：１，３－双［４－二甲胺苯基］－２，４二羟基环丁二烯氢氧双内盐（ＤＭＣＳ），１，３－双［４－双十六烷胺苯基］－２，４二羟基环丁二烯氢氧双内盐（ＤＨＣＳ）。研究了ＤＭＣＳ和ＤＨＣＳ在不同溶剂中的光物理行为，估算了ＤＭＣＳ、ＤＨＣＳ的基态与激发态之间偶极矩差值。在ＣＴＡＢ胶束中，除ＤＭＣＳ单体分子外，ＤＭＣＳ形成了二聚体。在二氧六环－水体系中，研究了ＤＨＣＳ的簇集行为，并测定了ＤＨＣＳ的临界簇集组成（Ｃ＿ψ）及临界簇集浓度（Ｃ＿Ａ）     

基于FPGA的GIFT分组密码算法实现

GIFT算法作为PRESENT算法的改进版本,结构上更加简洁高效,在FPGA上运行时,性能仍然存在提升空间。对此提出了一种新的实现方案,通过将算法的40轮迭代计算优化为20轮迭,并将加解密与轮密钥生成操作并行执行。在xc6slx16 FPGA平台综合后,频率可达194 MHz,吞吐量可达1.2 Gbps,消耗时钟周期21个,结果表明,所提方法相比现有工作具有更好的性能表现和更少的时钟周期消耗,实现在FPGA上高速运行是切实可行的。     

刚玉瓷指痕缺陷的研究

本文采用两种不同Al2O3粉为原料，结合Al2O3预烧与材料的生产工艺，对刚玉瓷的指痕缺陷及其对材料性能的影响进行了研究。结果发现：Al2O3粉预烧温度不匀时，部分颗粒（γ-Al2O3）周边存在层错缺陷，激活能的存在，人体中颗粒粘连（团聚）；该团聚体在坯体及烧结体中的残留直接引起烧结体中的结构缺陷，由Al2O3预烧温度高且均匀的粉体制备材料，才能获得具有优良性能的刚玉体。     

EFFECT OF NONSOLVENT ADDITIVES ON THE PORE SIZE AND THE PORE SIZE DISTRIBUTION OF AROMATIC POLYAMIDE RO MEMBRANES

In this paper discussions are made on the effect of nonsolvent swelling agents on the average pore size and pore size distributions at the surface of polyamide membranes which result from casting solutions involving above nonsolvent swelling agents.

The size of the polymer aggregate in the film casting solution and the size of polymer network pores are correlated to physicochemical data of ions which constitute the electrolytes used as nonsolvent swelling agents. As such ionic properties the charge density and the free energy of transition of ions from polyamide phase to water phase were considered. The validity of the correlation is limited in a range of casting solution composition where the polymer concentration in the casting solution is close to the limiting concentration of polymer at the phase boundary and the molar ratio of the nonsolvent swelling agent to the amide group involved in the polyamide polymer is equal to or slightly more than 0.7.     

Radial density distribution of fractal clusters

The radial density distributions of fractal clusters generated in both DLCA and RLCA conditions by Monte-Carlo off-lattice cluster-cluster aggregation have been investigated. It has been computed by averaging a large number of clusters of same mass to form an average cluster, which is then considered as spherically symmetric. It is found that the radial density distribution, calculated using the mass center of the cluster as the center point, does not follow the fractal scaling, as sometimes assumed in the literature. An empirical model has been proposed to describe the dependence of the radial density distribution on the number of particles in the cluster. The obtained radial density distribution is used to compute permeability profile of the fractal cluster using several literature models, which is then applied to estimate the cluster hydrodynamic radius, R_h, by considering the cluster as a porous permeable object and using the solution of Brinkman equations for the fluid flow inside the cluster. The so obtained R_h values are compared to those in the literature, computed using the Kirkwood-Riseman (KR) theory. It has been found that, among the five permeability models examined, only the model proposed by Davis (Proceedings of the Institution of Mechanical Engineers Part B 1, 185) provides results in good agreement with those obtained using the KR model. Furthermore, it has been verified that the R_h values are insensitive to the model used for the density distribution.     

再生混凝土力学性能提升技术与应用

针对大量混凝土废弃物造成生态环境日益恶化及天然骨料资源日益缺乏的问题,通过配制不同强度等级和不同再生骨料掺量的再生混凝土,并结合锡澄运河三级航道整治工程对再生混凝土力学性能及其提升技术进行试验研究。结果表明:再生骨料的掺量对C35及以下中低强度混凝土力学性能影响较小,而对C40及以上中高强度混凝土有较大影响,随再生骨料掺量的增加,再生混凝土力学性能降低;通过合理选用再生骨料级配、与天然骨料复掺、对再生骨料进行强化以及优化配合比参数等措施能提升混凝土力学性能;锡澄运河三级航道整治工程实际应用取得了很好的技术经济效益。     

再生骨料的基本物理力学性能试验研究

再生骨料的物理力学性质是影响其运用范围、再生混凝土性能的本质因素。通过对公路废弃混凝土所制成的再生骨料和天然骨料同时进行物理力学性能试验研究,获得了骨料的表观密度、吸水率、压碎值、磨耗损失和针片状颗粒含量值。通过对再生骨料和天然骨料的试验结果进行对比分析发现,再生骨料除了针片状颗粒含量值会略优于天然骨料,其他四种物理力学性质均比天然骨料差,但两者的差异性不大。     

后掺粗骨料工艺对高性能泵送混凝土性能影响研究

为解决建筑工程中高性能泵送混凝土的环境问题、成本问题,基于粗骨料嵌锁效应和界面水灰比强度理论,在保证高性能和泵送要求的条件下,提出了后掺骨料工艺,并对不同粗骨料后掺比例下的混凝土进行了力学性能和抗冻性能的研究。结果表明,随着粗骨料后掺比例的增大,7 d、28 d混凝土抗压强度持续增大,而28 d混凝土劈裂抗拉强度和抗折强度均呈先增大后减小的趋势;在冻融循环作用下,质量损失率的上升速率呈先减小后增大的趋势,而抗压、抗拉、抗折强度、动弹性模量以及超声波速的下降速率均呈先减小后增大的趋势。据此建议本C30高性能泵送混凝土的粗骨料最佳后掺比例为20%。