低轮FOX分组密码的碰撞-积分攻击

FOX是最近推出的系列分组密码，它的设计思想基于可证安全的研究结果，且在各种平台上的性能优良．本文利用碰撞攻击和积分攻击相结合的技术分析FOX的安全性，结果显示碰撞-积分攻击比积分攻击有效，攻击对4轮FOX64的计算复杂度是2^45.4，对5轮FOX64的计算复杂度是2^109.4，对6轮FOX64的计算复杂度是2^173.4，对7轮FOX64的计算复杂度是2^237.4，且攻击所需数据量均为2^9；也就是说4轮FOX64／64、5轮FOX64／128、6轮FOX64／192和7轮FOX64／256对本文攻击是不免疫的．

压缩函数局部平衡度与Hash函数平衡度的关系研究

主要探讨了基于MD方式构造hash函数时平衡度的保持问题，说明了压缩函数满足何种条件时hash函数能够取得最好的平衡度，提出了局部平衡度的概念，并利用此概念解决了压缩函数局部平衡度与hash函数平衡度的关系问题．这对于未来的hash函数的设计有非常重要的意义．

关于Noekeon分组密码

Noekeon是NESSIE公布的17个候选算法之一,讨论了Noekeon各个模块的密码特性及它们在整个密码中的作用,从中体会Noekeon的设计技巧.

N-烷基氮杂糖及其衍生物的合成

多羟基哌啶类化合物通常称为氮杂糖，由于与糖结构的相似性，亚胺基环醇表现出强的糖苷酶和糖基转移酶抑制活性，可调控在生物识别及酶结构控制中起到重要作用的糖蛋白的生物合成与水解。因此这类抑制剂有望成为与糖代谢紊乱有关的疾病的治疗药物，如：抗糖尿病、抗肿瘤、抗溶酶体贮积症及抗病毒感染（包括艾滋病）等药物。正是由于氮杂糖的重要生物活性及诱人的药用开发前景，近年来，有关氮杂糖及其衍生物的合成、生物活性及应用研究备受关注。 本论文探索了一系列的作为潜在的迈克加成中间体1-C-乙酰甲基/甲氧羰基甲基-5-N-取代呋喃核糖碳苷衍生物在碱的作用下先发生β-消除反应，接着发生分子内的迈克加成反应生成1-C-乙酰甲基-N-取代氮杂吡喃糖碳苷衍生物及1-C-甲氧羰基甲基-N-取代氮杂吡喃糖碳苷衍生物的方法，该转变过程为先通过β-消除得到非环状的α/β不饱和共轭酮或酯的中间体，接着5-N-取代氨基与分子内的α/β不饱和共轭酮或酯发生分子内的1,4-亲核加成，其中，2'-酯的环加成立体选择性的得到β型1-C-乙酰甲基-N-取代氮杂吡喃糖碳苷衍生物，而2'-酮的环加成得到立体异构体1-C-乙酰甲基-N-取代氮杂吡喃糖碳苷衍生物。此外，该类N-取代氮杂吡喃糖碳苷衍生物进一步脱除保护基，得到了一系列新的N-取代氮杂吡喃糖衍生物，拓展了氮杂吡喃糖碳苷分子库。 中间体1-C-(2'-oxoalkyl)-5-N-alkylated glycoribofuranoside的合成是由核糖为原料，通过对其结构修饰，在C-5氮原子上先引入不同的取代基，在C-1上引入乙酰甲基或甲氧羰基甲基。C-5取代氨基的引入通过两种方法：(a) 5-取代链状脂肪氨基可由链状的伯胺直接与5-甲磺酰基发生SN2亲核取代得到；(b) 5-取代芳香氨基可通过芳香醛与C-5氨基缩合再由硼氢化钠还原得到。2'-酰基的引入通过烯丙基氧化得到：2'-酮羰基由醋酸汞和琼斯试剂氧化得到；2'-酯基由高锰酸钾氧化再碘甲烷的作用下得到。 The polyhydroxylated piperidines, commonly be called azasugars. Iminocyclitols and their derivatives have exhibited remarkable biological activity to inhibit glycosidase-processing enzymes, with resulting potential chemotherapeutic applications against diabetes, cancer, lysosomal storage disorders and viral infections including AIDS. Recently, because of the important biological activity and excellent foreground on pharmaceutical application, great attention has been attracted to the synthesis of the new derivatives and analogues. In this dissertation, 1-C-(2'-oxoalkyl)-5-N-substituted-glycoribofuranosides, which used as latent substrates for intramolecular hetero-Michael addition, were converted to 2-ester and 2-ketone aza-C-glycopyranosides by base treatment. The transformation was achieved through β-elimination to an acyclic α/β-conjugated ketone or ester, followed by an intramolecular hetero-Michael addition by the 5-N-alkylated amino group. The 2-ester cycloaddition was highly stereoselective in favor of an equatorial 1-C-substitution while the 2-ketone cycloaddition was produced a pair of stereoisomers of 2′-ketonyl aza-C-glycoside. Additionally, the resultant different N-alkylated aza-C-glycopyranosides could be further prepared for various azasugar library constructions by removal of protecting groups. Synthesis of the key intermediate 1-C-(2'-oxoalkyl)-5-N-alkylated glycoribo- furanoside involved the introduction of 5-substituted amino and 1-C-2′-oxoalkyl groups from D-ribose. The 5-alkylated amino was introduced through two methods: (a) the 5-aliphatic series amino synthesized by the nucleophilic substitution of 5-mesylate using neat ethylamine, propylamine, butylamine, and hexylamine, (b) the 5-aromatic series amino synthesized by various aromatic aldehydes with C-5 amino under NaBH4 reduction. The 1-C-2′-oxoalkyl groups were introduced through oxidation of the ally group: the 1-C-allyl group was oxidized with Hg(OAc)2 and Jones reagent to the 2-ketonyl C-glycoside; the 1-C-allyl group was oxidized with KMnO4 and CH3I/NaHCO3 to 1-C-methyl acetate glycoside.

Degradation mechanism of polystyrene sulfonic acid membrane and application of its composite membranes in fuel cells

The lifetime behavior of a H-2/O-2 proton exchange membrane (PEM) fuel cell with polystyrene sulfonic acid (PSSA) membrane have been investigated in order to give an insight into the degradation mechanism of the PSSA membrane. The distribution of sulfur concentration in the cross section of the PSSA membrane was measured by energy dispersive analysis of X-ray, and the chemical composition of the PSSA membrane was characterized by infrared spectroscopy before and after the lifetime experiment. The degradation mechanism of the PSSA membrane is postulated as: the oxygen reduction at the cathode proceeds through some peroxide intermediates during the fuel cell operation, and these intermediates have strong oxidative ability and may chemically attack the tertiary hydrogen at the a carbon of the PSSA; the degradation of the PSSA membrane mainly takes place at the cathode side of the cell, and the loss of the aromatic rings and the SO3- groups simultaneously occurs from the PSSA membrane. A new kind of the PSSA-Nafion composite membrane, where the Nafion membrane is bonded with the PSSA membrane and located at the cathode of the cell, was designed to prevent oxidation degradation of the PSSA membrane in fuel cells. The performances of fuel cells with PSSA-Nafion101 and PSSA-recast Nafion composite membranes are demonstrated to be stable after 835 h and 240 h, respectively.

Zodiac算法新的Square攻击

该文重新评估了Zodiac算法抗Square攻击的能力。Zodiac算法存在8轮Square区分器,该文首先根据算法的结构特性,给出了Zodiac的4个等价结构,而后利用等价结构得到了两个新的9轮Square区分器。利用新的区分器,对不同轮数的Zodiac算法实施了Square攻击,对12轮,13轮,14轮,15轮和16轮Zodiac的攻击复杂度分别为237.3,262.9,296.1,2137.1和2189.5次加密运算,选择明文数分别为210.3,211,211.6,212.1和212.6。结果表明:完整16轮192bit密钥的Zodiac算法是不抗Square攻击的。

一种基于排队论的DoS攻防绩效评估方法

提出了一种新的基于排队论的DoS攻防绩效评估方法.针对不同种类DoS攻防手段建立了统一的指标体系和绩效计算方法,基于排队论方法分别建立评估模型,对UDP Flood和SYN Flood攻击的绩效进行不包含主观因素的定量评估,分析不同攻击手段和强度的有效性.针对典型DoS攻防场景,利用网络仿真工具进行模拟,通过实验与模型推导结果对比验证了排队论模型的合理性,并阐述了此方法在不同类型DoS攻防手段中的应用.

33轮SHACAL-2的差分非线性攻击

利用SHACAL-2的一个17轮差分非线性区分器,结合被猜测子密钥空间分割的方法和快速傅立叶变换,提出了一种攻击33轮SHACAL-2的新方法.该方法攻击33轮SHACAL-2需要244的选择明文、2496.6的33轮SHACAL-2加密和2502次算术运算,攻击成功概率为99%.与已有的结果相比较,新攻击有效地提高了单密钥下SHACAL-2的攻击轮数.

A Facile and Efficient Synthesis of Polyfunctionalized Pyridin-2(1H)-ones from β-Oxo Amides under Vilsmeier Conditions

A facile and efficient one-pot synthesis of polysubstituted pyridin-2(1H)-ones from a variety of beta-oxo amides under Vilsmeier conditions is described, and a mechanism involving sequential halogenation, formylation and intramolecular nucleophilic cyclization is proposed

Efficient and Divergent Synthesis of Fully Substituted 1H-Pyrazoles and

Efficient and divergent one-pot synthesis of fully substituted 1H-pyrazoles and isoxazoles from cyclopropyl oximes based on reaction conditions selection is reported. Under Vilsmeier conditions (POCl3/DMF), substituted 1H-pyrazoles were synthesized from 1-carbamoyl, 1-oximyl cyclopropanes via sequential ring-opening, chlorovinylation, and intramolecular aza-cyclization. In the presence of POCl3/CH2Cl2, substituted isoxazoles were obtained from the cyclopropyl oximes via ring-opening and intramolecular nucleophilic vinylic substitution (SNV) reactions

Efficient synthesis of α-alkylidene-β-lactams via NaOH-promoted intramolecular aza-Michael addition of α-carbamoyl ketene-S,S-acetals in aqueous media

A facile and efficient synthesis of substituted alpha-alkylidene-beta-lactams have been developed via a NaOH-promoted intramolecular aza-Michael addition of alpha-carbamoyl, alpha-(1-chlorovinyl) ketene-S,S-acetals and subsequent nucleophilic vinylic substitution (SNV) reaction in alcoholic aqueous media. (C) 2008 Elsevier Ltd. All rights reserved.

Vilsmeier Reaction of Enaminones: Efficient Synthesis of Halogenated Pyridin-2(1H)-ones

A facile and efficient one-pot synthesis of halogenated pyridin-2(1H)-ones from a series of readily available enaminones under Vilsmeier conditions is described, and a mechanism involving sequential halogenation, formylation, and intramolecular nucleophilic cyclization is proposed.