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基于两个数学难题的签名方案 总被引:1,自引:0,他引:1
Z.Shao提出了两种签名方案,并宣称它们的安全性是基于大数分解问题和离散对数问题的。其实,这两种签名方案在代换攻击下是不安全的。本文给出了伪造签名的公式,同时还提出了几种带有信息恢复功能的签名方案,它们的安全性是基于上述两个难题的,并且,它们在实施中的效率要比现有的方案好。 相似文献
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为增强安全性,基于双难题的签名方案相继被提出,如基于离散对数和素因子分解问题的签名方案,其安全目标是只要一个难题未被攻破,方案就是安全.分析表明:如果因子分解问题可解,杨刚和李艳俊提出的基于双难题的方案(YL)将被攻破;如果离散对数问题可解,LI和CHEN的方案(LC)不能抵抗伪造攻击.文中提出一种新的签名方案,该方案是真正同时基于双难题的,并能将消息恢复.通过分析,与其它方案相比,更加高效. 相似文献
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一种代理多签名体制的安全性分析 总被引:3,自引:0,他引:3
对Ji和Li的基于椭圆曲线离散对数问题的代理多签名体制提出了两个伪造攻击。利用这两个伪造攻击,任何一个原始签名人都能伪造出一个有效的代理多重数字签名。并对Ji和Li的代理多签名体制进行了改进,提出了新的安全的基于椭圆曲线离散对数问题的代理多签名体制。 相似文献
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冯登国 《信息安全与通信保密》1997,(1)
该文首先说明了Harn的分析方法对现有的基于离散对数问题的盲数字签名并没有带来真正的威胁。其次,基于一个登记协议和CarmenisCh等的盲数字签名方案,提出一个新型的公平盲数字签名方案,该方案提供了部分不可联系性。 相似文献
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本文基于离散对数问题提出了一 个新的(t,n)门限数字签名方案,该方案的一个突出优点是系统中的任何t个成员不能重构系统的秘密密钥。 相似文献
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The double-sided least-squares problem is formulated under a separability condition, using the properties of the Kronecker product to obtain the overall solution based on two standard subproblems. 相似文献
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《Solid-State Circuits, IEEE Journal of》1971,6(2):89-91
In the design of a class of sine-wave oscillators using resistors, capacitors, and operational amplifiers, there is either a direct tradeoff between the maximum component value and the dynamic range of signals with satisfactory sensitivity performance, or a direct tradeoff between the maximum component value and the sensitivity performance with satisfactory dynamic range. 相似文献
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交流声通常来自过载的电源供给器或有故障的放大器电源供给器。正规的故障查找需要使用一个优质的交、直流电压表,一个万用表和一个优质的可读取交流声数值的信号电平表。没有必要使用有效值读数的交流电压表;要精确地测量交流电压时需要用这种表,但是根据我们的经验,有一个相当好的非有效值读数的交流电压表就足够了,而且费用也小得多。一个技术人员一旦获得了当电压正常时交流表头上的读数应当是多少这种“感觉”以后,就不一定要使用真正的 相似文献
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The smallest grammar problem 总被引:2,自引:0,他引:2
Charikar M. Lehman E. Liu D. Panigrahy R. Prabhakaran M. Sahai A. Shelat A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2005,51(7):2554-2576
This paper addresses the smallest grammar problem: What is the smallest context-free grammar that generates exactly one given string /spl sigma/? This is a natural question about a fundamental object connected to many fields such as data compression, Kolmogorov complexity, pattern identification, and addition chains. Due to the problem's inherent complexity, our objective is to find an approximation algorithm which finds a small grammar for the input string. We focus attention on the approximation ratio of the algorithm (and implicitly, the worst case behavior) to establish provable performance guarantees and to address shortcomings in the classical measure of redundancy in the literature. Our first results are concern the hardness of approximating the smallest grammar problem. Most notably, we show that every efficient algorithm for the smallest grammar problem has approximation ratio at least 8569/8568 unless P=NP. We then bound approximation ratios for several of the best known grammar-based compression algorithms, including LZ78, B ISECTION, SEQUENTIAL, LONGEST MATCH, GREEDY, and RE-PAIR. Among these, the best upper bound we show is O(n/sup 1/2/). We finish by presenting two novel algorithms with exponentially better ratios of O(log/sup 3/n) and O(log(n/m/sup */)), where m/sup */ is the size of the smallest grammar for that input. The latter algorithm highlights a connection between grammar-based compression and LZ77. 相似文献
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《Spectrum, IEEE》2009,46(8):13-15
Jordan is in a tight spot. The virtually landlocked country is 80 percent desert, and the remaining 20 percent loses most of its rainfall to evaporation. The Dead Sea and the Jordan River, which feeds it, are drier than ever. With its population swelling with Iraqi migrants, water is Jordan's foremost concern. 相似文献
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