Quantitative description of desorption stages of coalbed methane is an important basis to objectively understand the production of coalbed methane well,to diagnose the production state,and to optimize the management o...Quantitative description of desorption stages of coalbed methane is an important basis to objectively understand the production of coalbed methane well,to diagnose the production state,and to optimize the management of draining and collection of coalbed methane.A series of isothermal adsorption experiments were carried out with 12 anthracite samples from 6 coalbed methane wells located in the south of the Qinshui Basin,based on the results of isothermal adsorption experiments,and an analytical model was developed based on the Langmuir sorption theory.With the model,a numerical method that adopts equivalent desorption rate and its curve was established,which can be used to characterize the staged desorption of coalbed methane.According to the experimental and numerical characterizations,three key pressure points determined by the equivalent desorption rate curvature that defines pressure-declining desorption stage,have been proposed and confirmed,namely,start-up pressure,transition pressure and sensitive pressure.By using these three key pressure points,the process of coalbed methane desorption associated with isothermal adsorption experiments can be divided into four stages,i.e.,zero desorption stage,slow desorption stage,transition desorption stage,and sensitive desorption stage.According to analogy analysis,there are differences and similarities between the processes of coalbed methane desorption identified by isothermal adsorption experiments and observed in gas production.Moreover,it has been found that larger Langmuir volume and ratio of Langmuir constants are beneficial to earlier advent of steady production stage,whereas it is also possible that the declining production stage may occur ahead of schedule.展开更多
The white-box attack is a new attack context in which it is assumed that cryptographic software is implemented on an un-trusted platform and all the implementation details are controlled by the attackers. So far, almo...The white-box attack is a new attack context in which it is assumed that cryptographic software is implemented on an un-trusted platform and all the implementation details are controlled by the attackers. So far, almost all white-box solutions have been broken. In this study, we propose a white-box encryption scheme that is not a variant of obfuscating existing ciphers but a completely new solution. The new scheme is based on the unbalanced Feistel network as well as the ASASASA （where ＂A＂ means affine, and ＂S＂ means substitution） structure. It has an optional input block size and is suitable for saving space compared with other solutions because the space requirement grows slowly （linearly） with the growth of block size. Moreover, our scheme not only has huge white-box diversity and white-box ambiguity but also has a particular construction to bypass public white-box cryptanalysis techniques, including attacks aimed at white-box variants of existing ciphers and attacks specific to the ASASASA structure. More precisely, we present a definition of white-box security with regard to equivalent key, and prove that our scheme satisfies such security requirement.展开更多
Since Multivatriate Quadratic(MQ)-based Public Key Cryptosystem(MPKC)has been one of the hot research fields of post-quantum cryptography,it becomes important to analyze the security of new MPKC schemes.Wang et al.pro...Since Multivatriate Quadratic(MQ)-based Public Key Cryptosystem(MPKC)has been one of the hot research fields of post-quantum cryptography,it becomes important to analyze the security of new MPKC schemes.Wang et al.proposed a novel multivariate signature scheme with Hash-based Tame Transformation and Minus(HTTM)in 2011.For this extended MQ-based signature,we can transform it into an SFLASH variant by splitting and merging HT transformation,and solve an equivalent private key corresponding to the public key of HTTM.Thus,the adversary can forge legitimate signature for any message by using this equivalent private key.展开更多
基金supported by National KeyBasic Research Program of China (Grant No. 2009CB219605)Key Project of National Natural Science Foundation of China (Grant No.40730422)Grand Science and Technology Special Project of China(Grant No. 2011ZX05034-04)
文摘Quantitative description of desorption stages of coalbed methane is an important basis to objectively understand the production of coalbed methane well,to diagnose the production state,and to optimize the management of draining and collection of coalbed methane.A series of isothermal adsorption experiments were carried out with 12 anthracite samples from 6 coalbed methane wells located in the south of the Qinshui Basin,based on the results of isothermal adsorption experiments,and an analytical model was developed based on the Langmuir sorption theory.With the model,a numerical method that adopts equivalent desorption rate and its curve was established,which can be used to characterize the staged desorption of coalbed methane.According to the experimental and numerical characterizations,three key pressure points determined by the equivalent desorption rate curvature that defines pressure-declining desorption stage,have been proposed and confirmed,namely,start-up pressure,transition pressure and sensitive pressure.By using these three key pressure points,the process of coalbed methane desorption associated with isothermal adsorption experiments can be divided into four stages,i.e.,zero desorption stage,slow desorption stage,transition desorption stage,and sensitive desorption stage.According to analogy analysis,there are differences and similarities between the processes of coalbed methane desorption identified by isothermal adsorption experiments and observed in gas production.Moreover,it has been found that larger Langmuir volume and ratio of Langmuir constants are beneficial to earlier advent of steady production stage,whereas it is also possible that the declining production stage may occur ahead of schedule.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos. 61272440, 61472251, and U1536101, and China Postdoctoral Science Foundation under Grant Nos. 2013M531174 and 2014T70417.
文摘The white-box attack is a new attack context in which it is assumed that cryptographic software is implemented on an un-trusted platform and all the implementation details are controlled by the attackers. So far, almost all white-box solutions have been broken. In this study, we propose a white-box encryption scheme that is not a variant of obfuscating existing ciphers but a completely new solution. The new scheme is based on the unbalanced Feistel network as well as the ASASASA （where ＂A＂ means affine, and ＂S＂ means substitution） structure. It has an optional input block size and is suitable for saving space compared with other solutions because the space requirement grows slowly （linearly） with the growth of block size. Moreover, our scheme not only has huge white-box diversity and white-box ambiguity but also has a particular construction to bypass public white-box cryptanalysis techniques, including attacks aimed at white-box variants of existing ciphers and attacks specific to the ASASASA structure. More precisely, we present a definition of white-box security with regard to equivalent key, and prove that our scheme satisfies such security requirement.
基金Supported by the National Natural Science Foundation of China(No.61142007)Natural Science Foundation of Universities of Jiangsu Province(13KJB520005)the Research Fund for the Graduate Innovation Program of Jiangsu Province(CXZZ13_0493)
文摘Since Multivatriate Quadratic(MQ)-based Public Key Cryptosystem(MPKC)has been one of the hot research fields of post-quantum cryptography,it becomes important to analyze the security of new MPKC schemes.Wang et al.proposed a novel multivariate signature scheme with Hash-based Tame Transformation and Minus(HTTM)in 2011.For this extended MQ-based signature,we can transform it into an SFLASH variant by splitting and merging HT transformation,and solve an equivalent private key corresponding to the public key of HTTM.Thus,the adversary can forge legitimate signature for any message by using this equivalent private key.
