基于遗传算法的机动弹头再入段弹道优化设计

针对机动弹头攻击区优化问题,设计了改进遗传算法加约束可变多面体法的串行混合遗传算法,采用直接优化方法,基于分段优化思想,对再入段最大纵程、最小纵程和最大横程等边界弹道分别进行了优化设计,得到了满足约束条件的最优边界弹道,从而确定了机动弹头的最大可攻击范围.优化结果表明,最大可攻击区范围是一个长半轴为17 km,短半轴为10 km的椭圆区域,此结果优于针对该弹头进行的大量弹道仿真所得的结论,可为进一步弹道设计提供参考依据.     

Optimal quantitative cryptanalysis of permutation-only multimedia ciphers against plaintext attacks

Recently, an image scrambling encryption algorithm of pixel bit based on chaos map was proposed. Considering the algorithm as a typical binary image scrambling/permutation algorithm exerting on plaintext of size M×(8N), this paper proposes a novel optimal method to break it with some known/chosen-plaintexts. The spatial complexity and computational complexity of the attack are only O(32·MN) and O(16·n₀·MN) respectively, where n₀ is the number of known/chosen-plaintexts used. The method can be easily extended to break any permutation-only encryption scheme exerting on plaintext of size M×N and with L different levels of values. The corresponding spatial complexity and computational complexity are only O(MN) and O(⌈log_L(MN)⌉·MN) respectively. In addition, some specific remarks on the performance of the image scrambling encryption algorithm are presented.     

C2密码防攻击技术研究

简要介绍了C2密码的概念,依据参考文献分析了针对C2密码的攻击方法,并为相关安全风险的防范提供了理论依据。     

Corrosion of stainless steel grades in H2O/KOH 50% at 120 °C: AISI304 austenitic and 2205 duplex

We report on the corrosion of austenitic (AISI304) and duplex (2205) stainless steels in H₂O/KOH 50% at 120 °C. The research is based on a combination of electrochemical, structural and compositional analyses, aimed at assessing the surface modifications resulting from anodic attack and their impact on corrosion resistance. Linear sweep voltammetry and electrochemical impedance spectrometry measurements were carried out in an air‐tight high‐temperature cell. In‐plane and cross‐sectional SEM micrography, X‐ray diffractometry and EDX profiling were used to characterise samples attacked under electrochemically controlled conditions. Electrochemical results have shown that AISI304 exhibits a complex passivating behaviour, while the anodic electrokinetics of the duplex is characterised by mixed kinetic control. AISI304 was found to fail by intergranular corrosion and to be covered: in passive conditions by acicular compounds and in transpassive conditions by a compact layer of corrosion products. Duplex samples, instead, exhibit an uniform form of corrosion morphology and bear a compact layer of corrosion products both in passive and in transpassive conditions.     

Security strategy of powered-off SRAM for resisting physical attack to data remanence

time of data remanence is reduced by 82% while the operation power consumption only increases by 7%.     

激光制导炸弹投放域计算方法研究

根据激光制导炸弹在空中的运动规律,首先将其在空中的六自由度运动方程分解为纵向、横向两个平面内的运动,然后结合激光制导炸弹的控制规律,得到其在空中弹道的数学模型.在VC++6.0环境下对此弹道进行仿真,再设计合适的算法求出激光制导炸弹投放域的边界,最终得出激光制导炸弹在横向、纵向两个平面内的可投放域.仿真结果显示出不同的投放条件对激光制导炸弹可投放域的影响,为攻击机投放激光制导炸弹的战术决策提供了一些依据.     

末段脉冲修正弹攻击区研究

为了确定采用激光半主动制导的末段脉冲修正弹的攻击区域,建立了导引头探测区模型,建立了六自由度有控弹道方程组,并提出了攻击区建模和仿真的方法.利用上述模型对不同条件下的攻击区进行了仿真计算与分析,结果表明增大导引头视场角、脉冲修正能力、启控点高度和发射条件都将影响攻击区的范围.     

对安全协议的一些新攻击

论文提出了很多对安全协议进行的新攻击，并且讨论将来如何避免设计不正确协议的方法。     

Parallel Collision Search with Cryptanalytic Applications

A simple new technique of parallelizing methods for solving search problems which seek collisions in pseudorandom walks is presented. This technique can be adapted to a wide range of cryptanalytic problems which can be reduced to finding collisions. General constructions are given showing how to adapt the technique to finding discrete logarithms in cyclic groups, finding meaningful collisions in hash functions, and performing meet-in-the-middle attacks such as a known-plaintext attack on double encryption. The new technique greatly extends the reach of practical attacks, providing the most cost-effective means known to date for defeating: the small subgroup used in certain schemes based on discrete logarithms such as Schnorr, DSA, and elliptic curve cryptosystems; hash functions such as MD5, RIPEMD, SHA-1, MDC-2, and MDC-4; and double encryption and three-key triple encryption. The practical significance of the technique is illustrated by giving the design for three $10 million custom machines which could be built with current technology: one finds elliptic curve logarithms in GF(2¹⁵⁵) thereby defeating a proposed elliptic curve cryptosystem in expected time 32 days, the second finds MD5 collisions in expected time 21 days, and the last recovers a double-DES key from two known plaintexts in expected time 4 years, which is four orders of magnitude faster than the conventional meet-in-the-middle attack on double-DES. Based on this attack, double-DES offers only 17 more bits of security than single-DES. Received 21 December 1995 and revised 24 September 1996     

氢蚀对15CrMo钢疲劳裂纹扩展寿命的影响

对15CrMo钢在氢蚀环境下和疲劳裂纹行为作了研究，重点考察了不同温度、压力和时间等情况下的扩展特性，并找出了对Paris公式中系数的影响趋势。