共查询到19条相似文献，搜索用时 203 毫秒
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吴文玲 《中国科学院研究生院学报》2001,18(2):181-185
对NTT公司近两年先后推出的分组密码算法E2和Camellia的特点及设计技巧进行了详细讨论.首先,指出Camellia的FL和FL-1函数的特点,利用此可以对Camellia进行中间相遇攻击;其次讨论E2和Camellia变形的安全性.结果显示如果采用一个S盒,则截断差分密码分析对10轮的Camellia*构成威胁;而设计者称10轮Camellia对截断差分密码分析是免疫的,这说明采用4个不同的S盒对Camellia的安全性起到很重要的作用.另一结果显示截断差分密码分析对12轮E2*构成威胁,这反映了扩散层P选取不但要求它的分支数,而且应尽力减少它的循环差分特征. 相似文献
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基于LBlock算法的轮函数结构,给出16轮和17轮的LBlock分组密码算法的中间相遇攻击方法.攻击16轮LBlock算法所需的数据量约为232,计算量约为244.5次16轮加密;攻击17轮LBlock算法所需的数据量约为232,计算量约为255.5次17轮加密.攻击结果表明,17轮的轮LBlock算法对中间相遇攻击是不免疫的. 相似文献
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对HIGHT进行了差分故障攻击.攻击采用单字节级的差分故障模型,在倒数第3轮和倒数第4轮进行故障诱导来恢复密钥.模拟实验结果显示采用大约32次故障诱导便可恢复密钥,分析的计算复杂度约为256.模加差分表预计算的复杂度为232. 相似文献
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余翀 《中国科学院研究生院学报》2013,30(3)
从硬件实现和软件算法两方面,对基于蜂窝地图的全方位步进式机器人系统进行设计实现.通过对6轮全向移动平台的力学、运动学和动力学分析建模,借助基于FPGA的高精度光电里程计和激光校准装置,设计出适合蜂窝地图下运行的全方位步进式机器人.结合多维度传感器的数据融合,在蜂窝栅格地图中分2个层次,分别进行基于“六向分块”思想的局部路径规划和基于遗传算法TSP优化问题的全局路径规划.实验证明了该系统在实际运行中的精确性和鲁棒性. 相似文献
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图像加密一直以来都是信息安全关注的热点,针对使用传统的混沌加密图像过程中出现的加密效果不佳的问题,本文采用基于分数阶的Fourier变换对图像像素进行置换矩阵,其次对置乱算法,扩散算法进行改进。在仿真实验中,将本文算法对Lean图进行加密处理,在算法统计分析,统计直方分析和抗差分性能分析等几个方面来说明本文算法具有的一定的优越性。 相似文献
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主要讨论基于身份的公钥加密系统的密钥撤销和密钥托管问题. 为解决上述问题, 提出一个该机的基于身份公钥加密体制的公钥加密方案 RS-PKC. 方案的安全性基于Bilinear Diffie-Hellman 问题的计算困难性假设. 并在随机谕示模型下, 证明了方案具有选择密文安全性. 相似文献
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采用比较研究的方法,结合案例分析、模型构建与推导,对N型、S型两类典型知识建构路径及其机理进行了剖析,同时对两类知识建构模式在复杂情境中的知识创造作用进行了比较研究,在此基础上,从复杂性吸收、不确定性利用等视角研究了企业组织在知识建构过程中的"复杂性降阶"行为效率问题。 相似文献
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JAVA语言是一种广泛应用的编程语言,具有其平台无关性的特点。RSA(Rivest-Shamir-Adleman)算法是一种基于"大数不可能质因数分解假设"的公匙体系。通过编写JApplet类程序,实现了在浏览器上通过编辑文本区明文,生成密钥对、电子邮件加密、电子邮件解密,用RSA加密算法实现电子邮件加密与解密的通用程序系统。 相似文献
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提出了求解一维抛物型方程的一族三层九点隐式格式。格式的截断误差为O(τ~2+h~4)。利用Fourier方法证明了当r 1/3时,差分格式是稳定的。通过数值试验,比较了差分格式的解与精确解的差别,说明了差分格式的有效性。 相似文献
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D.J.J. Farnell F.N. Hatfield M. Reakes D. Parry 《Journal of The Franklin Institute》2008,345(7):748-765
We employed multiscale line operators (MSLO) in order to segment blood vessels in digital fundus images. Separately, a median filter technique was used in order to provide results that were compared to those of the MSLO. The green channel of the colour image was used, and both sets of results were further enhanced by subsequently employing a simple “randomly seeded” region-growing algorithm. We applied this approach to two sets of retinal images, namely, the ARIA (www.eyecharity.com/aria_online/) and STARE (www.ces.clemson.edu/∼ahoover/stare/) retinal image archives. The ARIA dataset contained colour fundus images from healthy subjects, diabetic subjects, and age-related macular degeneration (AMD) subjects. Similarly, the STARE dataset contained images from both “normal” (i.e., healthy) and “abnormal” (i.e., diseased) eyes. Manual segmentations of the blood-vessel structure for all images in the ARIA and STARE datasets were obtained by a retinal image interpretation expert. These images were then taken to be our gold standards. Receiver-operator characteristic (ROC) curves were determined and the areas under the ROC curve (AZ) were obtained. A large increase in efficiency for our MSLO algorithm was observed for the entire datasets (ARIA AZ=0.899; STARE AZ=0.953) compared to basic thresholding alone (ARIA AZ=0.608; STARE AZ=0.753). Interestingly, the simple median filter algorithm followed by region growing also performed well (ARIA AZ=0.888; STARE AZ=0.947). Our results compared favourably to those results of previous segmentation procedures for the STARE dataset. As expected, the best results were found for the healthy control group for ARIA and for the normal subjects for STARE. 相似文献
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针对各向异性扩散方程抑制SAR图像相干斑时,需要进行多次迭代,很难用于实时处理的情况,提出一种改进算法.该算法根据图像变差系数,自适应调整中心像素与各方向扩散系数的权重,从而在均匀区域加速扩散过程,在非均匀区域保留原各向异性扩散方程的性能.利用机载SAR图像对算法性能进行验证,结果表明,算法仅需较少的迭代次数,就可以获得与常规各向异性扩散方程相干斑抑制相同的性能. 相似文献
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当前我国对外资国民待遇问题的研究,存在着追求发达国家所要求的全面国民待遇之倾向,由此也导致了对国民待遇认识上的偏差以及对我国外资待遇法律实践的不客观评价。本文以为,我国已经给予了外资国民待遇,现在所要做的只是将这个事实法律化而已。 相似文献
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从古希腊哲学对世界本源追寻的方面解读巴门尼德变化在逻辑上的不可能．我们看到其理论的合理性所在。虽然巴门尼德的变化在逻辑上不可能的观点．被后人所不认同．但巴门尼德学说中却存在着绝大的真理。 相似文献
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AbstractIn this Perspective paper we propose a rethink on how we should approach digital and analog news. Although there are literatures that continue to focus on the many and varied characteristics of digital and analog news, we should not consider these as separate, opposing entities. In fact, the intertwining between the digital and the analog of news makes it difficult, if not impossible, to define separately what they are, even if this often is the practice in scholarly debate on news and journalism in new media. What we argue in this paper is that today, in opposition to binary definitions, it would be much more revealing, and also connected to actual media practices, to try to understand how much digital there is in the analog news and, vice versa, how much analog there is in digital news. This approach recognizes three dimensions in media platforms: digital, analog, and, between them, a cross-evolved, digitalized analog present in television, radio, and online newspapers. Recognizing these three dimensions enables us to explore more clearly the implications that the hybridization of digital and analog news has on the overall media system and on the state of news itself. 相似文献
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Enric Junqué de Fortuny Tom De Smedt David Martens Walter Daelemans 《Information processing & management》2014
Despite the fact that both the Efficient Market Hypothesis and Random Walk Theory postulate that it is impossible to predict future stock prices based on currently available information, recent advances in empirical research have been proving the opposite by achieving what seems to be better than random prediction performance. We discuss some of the (dis)advantages of the most widely used performance metrics and conclude that is difficult to assess the external validity of performance using some of these measures. Moreover, there remain many questions as to the real-world applicability of these empirical models. In the first part of this study we design novel stock price prediction models, based on state-of-the-art text-mining techniques to assert whether we can predict the movement of stock prices more accurately by including indicators of irrationality. Along with this, we discuss which metrics are most appropriate for which scenarios in order to evaluate the models. Finally, we discuss how to gain insight into text-mining-based stock price prediction models in order to evaluate, validate and refine the models. 相似文献
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通过对近十年中国工程院增选院士地区分布的实证分析发现,我国工程科技正处全面发展的历史时期;同时我国的工程科技领域也存在一定的马太效应。对此我们必须采取措施,有效地规避马太效应,进一步促进我国工程科技的全面发展。 相似文献
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