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对16轮PRESENT算法差分分析的改进
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作者 田亚 陈少真 戴艺滨 《密码学报》 CSCD 2016年第6期573-583,共11页
PRESENT算法是一个SPN结构的轻量级分组密码算法,适用于计算资源有限的环境与设备.差分分析是攻击分组密码最为基本和有效的方法之一,对于迭代31轮的PRESENT算法,目前最好的差分分析结果是16轮,使用明文全空间2^(64)个选择明文.本文在... PRESENT算法是一个SPN结构的轻量级分组密码算法,适用于计算资源有限的环境与设备.差分分析是攻击分组密码最为基本和有效的方法之一,对于迭代31轮的PRESENT算法,目前最好的差分分析结果是16轮,使用明文全空间2^(64)个选择明文.本文在原有差分分析结果的基础上,根据线性P置换的扩散性质,得出在相邻两轮中活动S盒的数目与S盒差分值的汉明重量之间的关系.搜索差分路径时取不同位置的活动S盒,比较6轮差分路径的结果,在得到最多结果的位置上寻找14轮概率为2^(-62)的差分路径,从解密方向找到119个,从加密方向找到28个.在成功率为99%的情况下,将16轮多差分输入值-单差分输出值分析结果的数据量由原来的2^(64)个选择明文降低到2^(59.16)个,时间复杂度由原来的2^(64)次内存访问降低到2^(59.16)次,存储复杂度由原来的2^(32)个6比特计数器降低到2^(32)个3比特计数器.同时给出单差分输入值-多差分输出值的差分分析结果,数据量为2^(61.16)个选择密文,时间复杂度为2^(61.16)次内存访问,存储复杂度为2^(32)个4比特计数器. 展开更多
关键词 分组密码 present算法 差分分析 多差分输入值-单差分输出值
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On the feasibility of re-stimulation of shale wells 被引量:4
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作者 Mohammad O.Eshkalak Umut Aybar Kamy Sepehrnoori 《Petroleum Science》 SCIE CAS CSCD 2015年第3期553-559,共7页
As a result of advances in horizontal comple- tions and multi-stage hydraulic fracturing, the U.S. has been able to economically develop several decades of worth of natural gas. However, a considerable concern has ris... As a result of advances in horizontal comple- tions and multi-stage hydraulic fracturing, the U.S. has been able to economically develop several decades of worth of natural gas. However, a considerable concern has risen on the economic viability of shale gas development for reasons associated with the fast production declines as well as recent down-turns of natural gas prices besides rises in the costs of new technologies. Therefore, an economic analysis is required to investigate the profitability of the re- fracturing treatment of unconventional gas resources. Net present value of cash flows and internal rate of return are calculated for a range of gas prices considering 20 years of natural gas production from a typical unconventional shale gas reservoir. A systematic comparison is then accom- plished for three scenarios: (1) re-fracturing versus no re- fracturing, (2) combination of re-fracturing and drilling new wells, and (3) time-dependent re-fracturing treatment. Further, this paper incorporates the cost of re-fracturing treatment, the cost of drilling a new horizontal well, the water treatment cost, as well as the current and future price of natural gas in the model. The findings of this work would help the future re-stimulation development plans of the emerging unconventional shale gas plays. 展开更多
关键词 Economic analysis - Unconventional shaleassets Hydraulic re-fracturing - Net present value Internal rate of return
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On the Current Situation of Basic - level Administrative Law Enforcement in China
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作者 Xiaoxing Xie 《International Journal of Technology Management》 2016年第11期36-37,共2页
With the development of economy and society, our country is on the road of rule by law, the legal system is progressing constantly. At the same time, we should also see that the administration according to law is not ... With the development of economy and society, our country is on the road of rule by law, the legal system is progressing constantly. At the same time, we should also see that the administration according to law is not perfect, and its shortcomings exist in different degree and need to be further improved. Based on the analysis of the status quo of grass-roots administrative law enforcement in China, this paper tries to put forward corresponding countermeasures, so as to promote the work of law-based administration for the corresponding study. 展开更多
关键词 grass - roots level administrative law enforcement present situation
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