Hash差分攻击算法研究

Hash函数广泛应用于商业.军事等领域,因此对Hash算法的攻击在理论上和实际应用上都有重要的意义.自王小云教授提出差分攻击算法并攻破SHA-1,MD5,RIPEMD,MD4以来,对该算法的研究日益受到关注.然而王教授没有给出如何寻找差分和差分路径的方法.国内外专家都猜测她是靠非凡的直觉手工完成的,如何寻找差分和差分路径的方法成为关注的热点.构造差分路径涉及到如何处理差分循环移位和选择高概率的充分条件.业已证明,一般情况下,差分位移后有4种情况,并给出了4种情况的概率,最后比较了4种情况的概率.     

针对51步RIPEMD-160区分攻击的复杂度分析

SASAKI Y等人使用消息修改技术对51步RIPEMD-160算法进行区分攻击时(Lecture Notes in Computer Science,Vol.7341),未考虑模减差分对差分路线的影响,不能保证左右操作前半部分成立的概率为1,导致所得到的复杂度有误。为此,通过2-dimension sums方法构建RIPEMD-160区分器,在此基础上提出一种改进的区分攻击复杂度分析方法。给出保证差分路线中模减差分成立的充分条件,使消息修改后左右操作差分路线前半部分成立的概率由2~(-7.717)增加到1,从而提高区分器成立概率,同时通过实验测试得到后半部分差分路线成立的概率。分析结果表明,51步RIPEMD-160算法区分攻击的复杂度为2~(152.672)。     

BLAKE抗线性化差分分析安全性研究

基于模加、循环及异或运算的系统(ARX系统)通常被认为是设计密码算法的重要基础。在SHA-3第二轮候选算法中,BLAKE等杂凑函数基于该系统设计。通过对BLAKE-32中的模加运算进行线性化,分析了初始差分在各轮运算过程中的扩散情况,得出了初始状态字存在差分时各轮运算中差分的扩散特征。在此基拙上,研究了多次加法运算的线性化逼近概率,并分析了线性化逼近方法对分析算法的有效性。研究表明,线性化情况下,部分初始差分字在BLAKE-32中的扩散效果并不理想,可以将BLAKE算法局部线性化后进行差分攻击。     

MD5碰撞攻击中的充要条件集

通过分析MD5中非线性函数的性质以及模2³²减差分和异或差分的性质,证明了Liang Jie和Lai Xuejia 给出的产生MD5碰撞的充分条件集中的条件是保证第23～62步的差分路径满足的充要条件,给出了保证第63、64步的输出差分满足的充要条件集.利用得到的充要条件集,提出了对MD5的改进的碰撞攻击算法,该算法的平均计算复杂度约为已有碰撞攻击算法的0.718 7倍,并通过实验对该算法的改进效果进行了验证.     

基于MILP方法的LED密码安全性分析

基于自动化搜索算法求解差分特征与线性逼近,成为了分组密码的差分与线性攻击研究热点。提出一种面向半个字节MILP模型自动化搜索密码算法的差分特征与线性逼近方法,对轻量级LED密码进行分析,以较少的变量与约束不等式求解活跃S盒数量,4轮运算至少有25个活跃S盒,这个结果与算法设计者给出的活跃S盒理论值相同,验证了该方法的正确性。最后,计算LED算法的最大差分特征及线性逼近概率,证明其能够抵抗差分与线性攻击。     

SHA-3的安全性分析*

为分析Hash函数新标准SHA-3算法的安全性,从算法统计性能和轮函数Keccak-f的对称性两个方面对其进行测试。测试结果表明,SHA-3算法雪崩效应良好,平均变化比特数和平均变化概率都非常接近理想值且方差比较小,具有较高的稳定性和较低的碰撞程度; Keccak-f中添加常数的变换会严重扰乱轮函数的对称性,利用轮函数对称性对SHA-3进行内部差分攻击只适用于轮数较少的情况。     

SHA-1差分路径搜索算法和连接策略研究

Hash函数SHA-1的攻击技术研究一直受到密码分析者的广泛关注,其中,差分路径构造是影响攻击复杂度大小的重要环节.提出了带比特条件的全轮差分路径构造方法,统一了第1轮差分路径构造和后3轮的差分路径构造.该方法既与原有第1轮路径构造相容,又能省去后3轮路径约简、消息约简等繁琐技术环节,具有良好的兼容性.此外,综合考虑状态差分、布尔函数差分与比特条件之间的制约关系,提出了带比特条件的前向扩展、后向扩展和中间连接这3个子算法,并提出3个指标——比特条件的更新次数、扩展结果的相容性和候选集合的正确率对中间连接的成功率进行评价,结合提前终止策略,提出了最优的中间连接算法.理论分析结果表明,该方法有助于提高SHA-1差分路径构造的成功率.最后,采用该算法进行路径搜索,可以得到正确的可用于碰撞搜索的差分路径.     

改进Twister碰撞攻击技术

Twister是SHA-3候选算法中的一个典型的基于AES结构的分组密码算法。介绍Twister算法现有攻击技术,并对计算复杂度进行分析。运用反弹攻击,设计了一种可行的差分路径,对Twister算法圈的碰撞攻击进行分析,得到计算复杂度分别为2128和2184的圈碰撞。基于此对Twister压缩函数的碰撞攻击进行分析,可以降低其计算复杂度。     

一类SHA-x改进杂凑算法的设计及分析

在SHA-1和SHA-2标准算法的基础上,提出一类SHA-x改进杂凑算法的设计。该算法重新设计了杂凑函数Hash值的生成方法,将输出消息摘要的长度从SHA-1的160bit提高到192bit,同时保留了SHA-1模2^32加法的计算特性,以保证整个算法的加密速度。安全性分析表明,新设计的杂凑算法在不过分减慢加密速度的前提下,具有较SHA-1更好的抗攻击能力。     

SHA-3轮函数中ρ、π及χ变换的逆变换

Keccak自2012年被宣布为新一代Hash函数标准SHA-3后受到密码学界的高度关注,成为当前Hash函数研究的热点。文中给出了SHA-3轮函数中ρ、π和χ三个变换的逆变换。ρ变换只在同一道内沿z轴正向循环移位,故依据其移位距离表沿z轴负方向移位同样距离即得到其逆变换ρ-1;π变换依赖于GF（5）上一个2阶变换矩阵,利用高斯消元法对此方阵求逆可得到其逆矩阵,也即得到了π变换的逆变换;χ变换是SHA-3轮函数中唯一的非线性变换,首先列出χ变换的真值表,然后通过真值表推导得出了其逆变换χ-1的布尔函数表达式。基于ρ^-1、π^-1和χ^-1,可利用中间相遇攻击的思想构造差分路径对SHA-3进行攻击,通过消息修改技术使差分路径以概率1通过χ-1,能够大大提高攻击成功的概率。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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