安胜安全操作系统是自主研制的基于 Linux 的高安全等级安全操作系统,包括安全内核,安全架构与安全模型.总结了对该系统进行的隐蔽通道分析方法,首次报道基于 Linux 内核开发的安全操作系统的隐蔽通道分析结果.应用新型的“回溯方法”...安胜安全操作系统是自主研制的基于 Linux 的高安全等级安全操作系统,包括安全内核,安全架构与安全模型.总结了对该系统进行的隐蔽通道分析方法,首次报道基于 Linux 内核开发的安全操作系统的隐蔽通道分析结果.应用新型的“回溯方法”发现了某些新的隐蔽通道.对被标识的隐蔽通道,准确地计算了它们的带宽,并进行了适当的隐蔽通道处理.展开更多
Based on the data of suspended sediment transport and channel sedimentation in various grain size fractions in the period of 1962―1985, the relationship between channel sedimentation in the lower Yellow River and sed...Based on the data of suspended sediment transport and channel sedimentation in various grain size fractions in the period of 1962―1985, the relationship between channel sedimentation in the lower Yellow River and sediment input has been plotted with respect to each grain size fraction. Several fill-scour thresholds in sediment input have been identified from these graphs. It was found that the fill-scour threshold in sediment input decreases with the increase in fraction grain size. The correlation coefficient between channel sedimentation and sediment input becomes larger with the increasing fraction grain size, indicating that channel sedimentation depends more on coarser grain size fractions than on smaller ones. The fraction channel sedimentation induced by unit change of fraction sediment input increases with grain size. Of the input of sediment larger than 0.025 mm, 43.73% was deposited on the channel, and for inputs of sediments larger than 0.05 mm and larger than 0.10 mm, 76.61% and 97.68% were deposited on the channel, respectively. Thus, for reduction of each ton of sediment larger than 0.10 mm from the drainage basin, the resultant reduction in channel sedimentation in the lower Yellow River would be 1.275 times that for the sediment larger than 0.10 mm, and 2.234 times that for the sediment larger than 0.025 mm. Therefore, if the erosion and sediment control measures are enforced in the areas where >0.05 or >0.10 mm sediment is produced, then the best beneficial will be achieved in reducing sedimentation in the lower Yellow River.展开更多
The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide(CO_(2))emissions in the northeastern Ordos Basin.The geological storage of CO_(2) in saline aquifers is an ef...The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide(CO_(2))emissions in the northeastern Ordos Basin.The geological storage of CO_(2) in saline aquifers is an effective backup way to achieve carbon neutrality.In this case,the potential of saline aquifers for CO_(2) storage serves as a critical basis for subsequent geological storage project.This study calculated the technical control capacities of CO_(2) of the saline aquifers in the fifth member of the Shiqianfeng Formation(the Qian-5 member)based on the statistical analysis of the logging and the drilling and core data from more than 200 wells in the northeastern Ordos Basin,as well as the sedimentary facies,formation lithology,and saline aquifer development patterns of the Qian-5 member.The results show that(1)the reservoirs of saline aquifers in the Qian-5 member,which comprise distributary channel sand bodies of deltaic plains,feature low porosities and permeabilities;(2)The study area hosts three NNE-directed saline aquifer zones,where saline aquifers generally have a single-layer thickness of 3‒8 m and a cumulative thickness of 8‒24 m;(3)The saline aquifers of the Qian-5 member have a total technical control capacity of CO_(2) of 119.25×10^(6) t.With the largest scale and the highest technical control capacity(accounting for 61%of the total technical control capacity),the Jinjie-Yulin saline aquifer zone is an important prospect area for the geological storage of CO_(2) in the saline aquifers of the Qian-5 member in the study area.展开更多
In cloud storage,client-side deduplication is widely used to reduce storage and communication costs.In client-side deduplication,if the cloud server detects that the user’s outsourced data have been stored,then clien...In cloud storage,client-side deduplication is widely used to reduce storage and communication costs.In client-side deduplication,if the cloud server detects that the user’s outsourced data have been stored,then clients will not need to reupload the data.However,the information on whether data need to be uploaded can be used as a side-channel,which can consequently be exploited by adversaries to compromise data privacy.In this paper,we propose a new threat model against side-channel attacks.Different from existing schemes,the adversary could learn the approximate ratio of stored chunks to unstored chunks in outsourced files,and this ratio will affect the probability that the adversary compromises the data privacy through side-channel attacks.Under this threat model,we design two defense schemes to minimize privacy leakage,both of which design interaction protocols between clients and the server during deduplication checks to reduce the probability that the adversary compromises data privacy.We analyze the security of our schemes,and evaluate their performances based on a real-world dataset.Compared with existing schemes,our schemes can better mitigate data privacy leakage and have a slightly lower communication cost.展开更多
With its wider acceptability,cloud can host a diverse set of data and applications ranging from entertainment to personal to industry.The foundation of cloud computing is based on virtual machines where boundaries amo...With its wider acceptability,cloud can host a diverse set of data and applications ranging from entertainment to personal to industry.The foundation of cloud computing is based on virtual machines where boundaries among the application data are very thin,and the potential of data leakage exists all the time.For instance,a virtual machine covert timing channel is an aggressive mechanism to leak confidential information through shared components or networks by violating isolation and security policies in practice.The performance of a covert timing channel(covert channel)is crucial to adversaries and attempts have been made to improve the performance of covert timing channels by advancing the encoding mechanism and covert information carriers.Though promising,the redundancy of the covert message is mainly overlooked.This paper applies three encoding schemes namely run-length,Huffman,and arithmetic encoding schemes for data compression of a virtual machine covert timing channel by exploiting redundancy.Accordingly,the paper studies the performance of such channels according to their capacity.Unfortunately,we show that these encoding schemes still contain redundancy in a covert channel scenario,and thereby a new encoding scheme namely optimized Runlength encoding(OptRLE)is presented that greatly enhances the performance of a covert timing channel.Several optimizations schemes adopted by OptRLE are also discussed,and a mathematical model of the behavior of an OptRLE-based covert timing channel is proposed.The theoretical capacity of a channel can be obtained using the proposed model.Our analysis reveals that OptRLE further improves the performance of a covert timing channel,in addition to the effects of the optimizations.Experimental result shows how OptRLE affects the size of covert data and the capacity of covert timing channels,and why the performance of the covert timing channel is improved.展开更多
文摘安胜安全操作系统是自主研制的基于 Linux 的高安全等级安全操作系统,包括安全内核,安全架构与安全模型.总结了对该系统进行的隐蔽通道分析方法,首次报道基于 Linux 内核开发的安全操作系统的隐蔽通道分析结果.应用新型的“回溯方法”发现了某些新的隐蔽通道.对被标识的隐蔽通道,准确地计算了它们的带宽,并进行了适当的隐蔽通道处理.
基金Supported by the National Natural Science Foundation of China (Grant No. 50725930) Chinese Ministry for Science and Technology (Grant No. 2006BA06B03)
文摘Based on the data of suspended sediment transport and channel sedimentation in various grain size fractions in the period of 1962―1985, the relationship between channel sedimentation in the lower Yellow River and sediment input has been plotted with respect to each grain size fraction. Several fill-scour thresholds in sediment input have been identified from these graphs. It was found that the fill-scour threshold in sediment input decreases with the increase in fraction grain size. The correlation coefficient between channel sedimentation and sediment input becomes larger with the increasing fraction grain size, indicating that channel sedimentation depends more on coarser grain size fractions than on smaller ones. The fraction channel sedimentation induced by unit change of fraction sediment input increases with grain size. Of the input of sediment larger than 0.025 mm, 43.73% was deposited on the channel, and for inputs of sediments larger than 0.05 mm and larger than 0.10 mm, 76.61% and 97.68% were deposited on the channel, respectively. Thus, for reduction of each ton of sediment larger than 0.10 mm from the drainage basin, the resultant reduction in channel sedimentation in the lower Yellow River would be 1.275 times that for the sediment larger than 0.10 mm, and 2.234 times that for the sediment larger than 0.025 mm. Therefore, if the erosion and sediment control measures are enforced in the areas where >0.05 or >0.10 mm sediment is produced, then the best beneficial will be achieved in reducing sedimentation in the lower Yellow River.
基金funded by the Top 10 key scientific and technological projects of CHN Energy in 2021 entitled Research and Demonstration of Technology for Carbon Dioxide Capture and Energy Recycling Utilization(GJNYKJ[2021]No.128,No.:GJNY-21-51)the Carbon Neutrality College(Yulin)Northwest University project entitled Design and research of large-scale CCUS cluster construction in Yulin area,Shaanxi Province(YL2022-38-01).
文摘The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide(CO_(2))emissions in the northeastern Ordos Basin.The geological storage of CO_(2) in saline aquifers is an effective backup way to achieve carbon neutrality.In this case,the potential of saline aquifers for CO_(2) storage serves as a critical basis for subsequent geological storage project.This study calculated the technical control capacities of CO_(2) of the saline aquifers in the fifth member of the Shiqianfeng Formation(the Qian-5 member)based on the statistical analysis of the logging and the drilling and core data from more than 200 wells in the northeastern Ordos Basin,as well as the sedimentary facies,formation lithology,and saline aquifer development patterns of the Qian-5 member.The results show that(1)the reservoirs of saline aquifers in the Qian-5 member,which comprise distributary channel sand bodies of deltaic plains,feature low porosities and permeabilities;(2)The study area hosts three NNE-directed saline aquifer zones,where saline aquifers generally have a single-layer thickness of 3‒8 m and a cumulative thickness of 8‒24 m;(3)The saline aquifers of the Qian-5 member have a total technical control capacity of CO_(2) of 119.25×10^(6) t.With the largest scale and the highest technical control capacity(accounting for 61%of the total technical control capacity),the Jinjie-Yulin saline aquifer zone is an important prospect area for the geological storage of CO_(2) in the saline aquifers of the Qian-5 member in the study area.
基金supported by the National Key R&D Program of China (No.2018YFA0704703)National Natural Science Foundation of China (Nos.61972215,61972073,and 62172238)Natural Science Foundation of Tianjin (No.20JCZDJC00640).
文摘In cloud storage,client-side deduplication is widely used to reduce storage and communication costs.In client-side deduplication,if the cloud server detects that the user’s outsourced data have been stored,then clients will not need to reupload the data.However,the information on whether data need to be uploaded can be used as a side-channel,which can consequently be exploited by adversaries to compromise data privacy.In this paper,we propose a new threat model against side-channel attacks.Different from existing schemes,the adversary could learn the approximate ratio of stored chunks to unstored chunks in outsourced files,and this ratio will affect the probability that the adversary compromises the data privacy through side-channel attacks.Under this threat model,we design two defense schemes to minimize privacy leakage,both of which design interaction protocols between clients and the server during deduplication checks to reduce the probability that the adversary compromises data privacy.We analyze the security of our schemes,and evaluate their performances based on a real-world dataset.Compared with existing schemes,our schemes can better mitigate data privacy leakage and have a slightly lower communication cost.
基金supported by the National Key Research and Development Program of China under Grant No.2017YFB0202103.
文摘With its wider acceptability,cloud can host a diverse set of data and applications ranging from entertainment to personal to industry.The foundation of cloud computing is based on virtual machines where boundaries among the application data are very thin,and the potential of data leakage exists all the time.For instance,a virtual machine covert timing channel is an aggressive mechanism to leak confidential information through shared components or networks by violating isolation and security policies in practice.The performance of a covert timing channel(covert channel)is crucial to adversaries and attempts have been made to improve the performance of covert timing channels by advancing the encoding mechanism and covert information carriers.Though promising,the redundancy of the covert message is mainly overlooked.This paper applies three encoding schemes namely run-length,Huffman,and arithmetic encoding schemes for data compression of a virtual machine covert timing channel by exploiting redundancy.Accordingly,the paper studies the performance of such channels according to their capacity.Unfortunately,we show that these encoding schemes still contain redundancy in a covert channel scenario,and thereby a new encoding scheme namely optimized Runlength encoding(OptRLE)is presented that greatly enhances the performance of a covert timing channel.Several optimizations schemes adopted by OptRLE are also discussed,and a mathematical model of the behavior of an OptRLE-based covert timing channel is proposed.The theoretical capacity of a channel can be obtained using the proposed model.Our analysis reveals that OptRLE further improves the performance of a covert timing channel,in addition to the effects of the optimizations.Experimental result shows how OptRLE affects the size of covert data and the capacity of covert timing channels,and why the performance of the covert timing channel is improved.
