一个新的具有前向安全有代理的多重数字签名方案

文章在研究有代理的多重数字签名的基础上,将前向安全的概念引人在有代理多重数字签名中,提出了一个具有前向安全性的有代理多重数字签名方案,在这种多重签名中,允许部分签名人委托其代理人进行签名．同时该方案能实现即使所有签名人的签名密钥被泄露,攻击者也无法伪造前阶段签名,以前所产生的有代理多重数字签名依然有效．     

强前向安全的椭圆曲线数字签名方案

为解决数字签名方案中的强前向安全问题,分析了一类基于椭圆曲线的前向安全数字签名方案,结果表明该方案不具备后向安全的性质。引入双私钥演化的方法,提出了一种具有强前向安全的椭圆曲线数字签名方案。安全性分析表明,改进方案具有强前向安全性和抗伪造性,同时满足后向安全的要求。     

基于Guillou-Quisquater体制的前向安全代理签名方案

对最近提出的一个前向安全强代理数字签名方案进行了安全性分析,发现该方案不具有前向安全性.提出了一个基于Guillou-Quisquater签名体制的前向安全代理数字签名方案,并分析了所提方案的安全性.     

一个基于GDH群的前向安全分布式数字签名方案

将一个基于GDH群的数字签名方案扩展到分布式数字签名中,并将前向安全的概念扩展到该签名方案中,提出一个有效的前向安全分布式签名方案.使用部分签名密钥安全前向更新,使集体签名安全前向更新,使得任何成员都不可能单独控制签名密钥的更新.增强密钥的安全性,使签名方案具有前向安全性.     

具有前向安全性质的限制次数代理签名方案

借鉴前向安全的数字签名的思想,利用已有的基于Fiat-Shamir的代理签名方案,引入两个验证参量,修改签名、验证等式及过程,构造了一个具有前向安全特性的代理签名方案。方案的安全性基于大整数因子分解的难度。在本方案中。代理签名者的代理密钥是前向安全的,代理签名者每签名一次即改变代理密钥,在代理签名中同时包含签名的次数,原始签名者通过公布允许签名的次数来限制代理签名者签名的次数。     

对前向安全数字签名方案的分析与改进

针对基于椭圆曲线的前向安全数字签名方案存在较为严重的安全性漏洞问题, 给出一种针对该前向安全 数字签名方案进行伪造签名的方法, 对其合理性和正确性进行了验证, 并对该方案进行了改进。 验证结果证 明, 改进后的方案足以抵御所提出的伪造签名方法, 从而提高了安全性。     

基于Guillou-Quisquater体制的前向安全数字签名方案

对具有前向安全的一种数字签名方案进行了密码分析,发现该方案存在安全隐患,不具有前向安全性。本文提出了一种新的基于Gu illou-Qu isquater体制的前向安全数字签名方案,新方案主要利用强RSA假定,通过签名私钥的有效更新来实现前向安全性。分析表明新方案具有较高的安全性。     

基于椭圆曲线密码体制的一种具有前向安全的数字签名方案

为了解决普通数字签名密钥被泄漏的局限性，作提出一种椭圆曲线数字签名方案，并基于前向安全理论提出一种具有前向安全的数字签名方案．新方案中用于数字签名的私钥由一个单向函数控制并随时间的推移按时间段不同不断地改变，而其相对应的公钥却保持不变，因此即使在某一时间段签名密钥被泄漏，攻击依然无法仿造先前时间段的签名，从而保证了以前时间段签名的安全性．中还分析了新方案的安全性，并证明了方案的有效性．     

对一种强前向安全的数字签名方案的分析及改进

针对强前向数字签名分析了密码学方案,对该方案提出了出现的错误,并对前向安全数字签名方案进行了改进。最后对新方案的安全性做了分析。     

一种多重数字签名方案的安全性分析

对Li和Yang最近提出的ElGamal多重数字签名方案^[1]，提出了一种伪造攻击，利用该伪造攻击，签名U1，U2，…，Un中任何一个签名都能伪造出一个有效的U1，U2，…，Un对消息m的多重数字签名．并对李子目和杨义先的多重数字签名方案进行了改进，提出了一种新的安全的多重数字签名方案．     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to