格理论最初是作为一种密码分析工具被引入到密码学中的,用于分析背包密码体制、RSA密码体制等.在1997年,Ajtai和Dwork第一次构造了一个基于格的密码体制Ajtai-Dwork,随后在1998年出现了NTRU密码体制.当时基于整数分解及离散对数的公钥...格理论最初是作为一种密码分析工具被引入到密码学中的,用于分析背包密码体制、RSA密码体制等.在1997年,Ajtai和Dwork第一次构造了一个基于格的密码体制Ajtai-Dwork,随后在1998年出现了NTRU密码体制.当时基于整数分解及离散对数的公钥密码体制是主流,格密码一直没有得到足够的重视.直到2009年,Gentry基于格密码构造了首个全同态密码方案,格密码才得到了广泛的发展.2015年,Peikert在"格密码十年"一文中,对之前格密码的发展做了一个很好的总结.同在2015年,美国国家标准和技术研究院(National Institute of Standards and Technology,NIST)发布了"后量子密码报告",报告指出:由于量子计算技术的飞速发展,现有的公钥密码标准在量子计算下将不再安全.同时NIST在全球范围内展开了后量子密码算法标准的征集工作.格密码作为一类经典的抗量子密码,公认是后量子密码算法标准最有力的竞争者,近2年得到了飞速的发展,出现了许多优秀的研究成果.从基于格的零知识证明、格加密、格签名以及格密钥交换4个方面,对近2年格密码研究进行了总结,并对格密码的发展趋势进行了展望.展开更多
随着移动计算和物联网等新兴技术的飞速发展,基于位置的服务(Location Based Service,LBS)在人们日常生活中扮演着愈发重要的角色。许多应用(如移动交友)通过LBS获取、收集用户的精确位置,并通过执行距离计算来实现近距离用户发现等功...随着移动计算和物联网等新兴技术的飞速发展,基于位置的服务(Location Based Service,LBS)在人们日常生活中扮演着愈发重要的角色。许多应用(如移动交友)通过LBS获取、收集用户的精确位置,并通过执行距离计算来实现近距离用户发现等功能。然而,LBS在为用户带来便利的同时,也使其面临着泄露隐私位置信息的风险。目前,大多数LBS应用均以明文形式记录用户精确位置,极易泄露用户的位置和移动模式等信息。此外,现有的能够保护用户隐私位置数据的研究工作存在一些缺陷,如通信开销高、通信时间长或计算安全性不足等。因此,文章提出一种保护用户位置隐私的高效近邻检测方法,该方法基于B/FV(Brakerski/Fan-Vercauteren)同态加密构造优化的圆范围内的隐私保护近邻检测协议。与现有的工作相比,文章方案使用基于格的加密,且具有较优的通信性能。此外,文章实现了基于B/FV同态加密的方案原型系统,并给出在具有高隐私保护要求和低算术速度限制的场景中的潜在应用,通过对该原型系统的实验结果表明,该方案在实际部署应用中具有广阔的应用前景。展开更多
To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direc...To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direct current method, we propose a new mesh refinement and recoarsement method for a two-dimensional point source. We introduce the mesh refinement and mesh recoarsement into the traditional structured mesh subdivision. By refining the horizontal grids, the singularity owing to the point source is minimized and the topography is simulated. By recoarsening the horizontal grids, the number of grid cells is reduced significantly and computational efficiency is improved. Model tests show that the proposed method solves the singularity problem and reduces the number of grid cells by 80% compared to the uniform grid refinement.展开更多
A complete mesh free adaptive algorithm （MFAA）, with solution adaptation and geometric adaptation, is developed to improve the resolution of flow features and to replace traditional global refinement techniques in s...A complete mesh free adaptive algorithm （MFAA）, with solution adaptation and geometric adaptation, is developed to improve the resolution of flow features and to replace traditional global refinement techniques in structured grids. Unnecessary redundant points and elements are avoided by using the mesh free local clouds refinement technology in shock influencing regions and regions near large curvature places on the boundary. Inviscid compressible flows over NACA0012 and RAE2822 airfoils are computed. Finally numerical results validate the accuracy of the above method.展开更多
Local mesh refinement is one of the key steps in the implementations of adaptive finite element methods. This paper presents a parallel algorithm for distributed memory parallel computers for adaptive local refinement...Local mesh refinement is one of the key steps in the implementations of adaptive finite element methods. This paper presents a parallel algorithm for distributed memory parallel computers for adaptive local refinement of tetrahedral meshes using bisection. This algorithm is used in PHG, Parallel Hierarchical Grid Chttp：//lsec. cc. ac. cn/phg/）, a toolbox under active development for parallel adaptive finite element solutions of partial differential equations. The algorithm proposed is characterized by allowing simukaneous refinement of submeshes to arbitrary levels before synchronization between submeshes and without the need of a central coordinator process for managing new vertices. Using the concept of canonical refinement, a simple proof of the independence of the resulting mesh on the mesh partitioning is given, which is useful in better understanding the behaviour of the biseetioning refinement procedure.展开更多
Public key encryption scheme with keyword search （PEKS） enables us to search the encrypted data in a cloud server with a keyword, and no one can obtain any infor- mation about the encrypted data without the trapdoor...Public key encryption scheme with keyword search （PEKS） enables us to search the encrypted data in a cloud server with a keyword, and no one can obtain any infor- mation about the encrypted data without the trapdoor corresponding to the keyword. The PEKS is useful to keep the management of large data storages secure such as those in a cloud. In this paper, to protect against quantum computer attacks, we present a lattice-based identity-based encryption scheme with key- word search. We have proved that our scheme can achieve ciphertext indistinguishability in the random oracle model, and our scheme can also achieve trapdoor security. In particular, our scheme can designate a unique tester to test and return the search results, therefore it does not need a secure channel. To the best of our knowledge, our scheme is the first iden- tity-based encryption scheme with keyword search from lattice assumption.展开更多
Security analysis of cryptographic protocols has been widely studied for many years.As far as we know,we have not found any methods to effectively analyze group key exchange protocols for the three parties yet,which d...Security analysis of cryptographic protocols has been widely studied for many years.As far as we know,we have not found any methods to effectively analyze group key exchange protocols for the three parties yet,which did not sacrifice the soundness of cryptography.Recently,Canetti and Herzog have proposed Universally Composable Symbolic Analysis(UCSA) of two-party mutual authentication and key exchange protocol which is based on the symmetric encryption schemes.This scheme can analyze the protocols automatically and guarantee the soundness of cryptography.Therefore,we discuss group key exchange protocol which is based on Joux Tripartite Diffie-Hellman(JTDH) using UCSA.Our contribution is analyzing group key exchange protocol effectively without damaging the soundness of cryptography.展开更多
In the era of big data, government, business and personal digital information will be possible for data mining. Data mining requires massive data as a support. However, the direct release of the original mass data, wh...In the era of big data, government, business and personal digital information will be possible for data mining. Data mining requires massive data as a support. However, the direct release of the original mass data, which usually contain some sensitive information of personal or analysis, will result in leakage of user privacy. Therefore, it is becoming increasingly important to protect privacy information in data publishing. In this paper, we focus on the multi-type self-identified format-preserving encryption. First, we introduce a multi-type self-identified format-preserving encryption system and discuss the encryption of various types of data in this system. Then, for the format preserving encryption(FPE) about Chinese name, we study from the encryption model construction and basic encryption scheme. The format-preserving encryption model about Chinese name is constructed and the concept of the name library is presented. Based on this, it is used to not only limit the message space to reduce complexity, but also ensure the cipher in accordance with the Chinese naming habits. In addition, according to the encryption and decryption model, format-preserving encryption process of Chinese name is designed. In order to add new names, the algorithm of name space expansion is proposed. Based on the Prefix, this paper put forward an algorithm named Cycle-Prefix, which enhances the security and dynamics of FPE by using two adjustment factors and the circular encryption. Compared with the traditional Prefix algorithm, experiments show that Cycle-Prefix can not only complete the task of FPE for Chinese name, but also encrypt same plain text into different ciphers under the premise of similar efficiency with Prefix.展开更多
Based on the relationship between cheating immune secret sharing and cryptographic criteria of Boolean functions, to design a cheating immune secret sharing scheme, a 1-resilient function satisfying the strict avalanc...Based on the relationship between cheating immune secret sharing and cryptographic criteria of Boolean functions, to design a cheating immune secret sharing scheme, a 1-resilient function satisfying the strict avalanche criterion （SAC） is needed. In this paper, a technique on constructing a cheating immune secret sharing function is studied. By using Maiorana-McFarland construction technique, two new methods to construct cheating immune secret sharing functions are proposed.展开更多
We present a self-synchronizing stream encryption scheme based on one-dimensional coupled map lattices which is introduced as a model with the essential features of spatiotemporal chaos, and of great complexity and di...We present a self-synchronizing stream encryption scheme based on one-dimensional coupled map lattices which is introduced as a model with the essential features of spatiotemporal chaos, and of great complexity and diffusion capability of the little disturbance in the initial condition. To evaluate the scheme, a series of statistical tests are employed, and the results show good random-look nature of the ciphertext. Furthermore, we apply our algorithm to encrypt a grey-scale image to show the key sensitivity.展开更多
Immersed boundary method is a crucial method to deal with particle suspension flow.Particle shapes involved in such flow are usually simple geometry,such as sphere and ellipsoid,which can be conveniently represented b...Immersed boundary method is a crucial method to deal with particle suspension flow.Particle shapes involved in such flow are usually simple geometry,such as sphere and ellipsoid,which can be conveniently represented by the triangular surface grid.When the number of particles and resolution of the surface grid increase,calculating the hydrodynamic force on the particle surface through integration can be time-consuming.Hence,the present paper establishes a fast mapping method to evaluate immersed boundary hydrodynamic force.Firstly,the particle surface grid is generated by an initial triangular element grid.Subsequently,the initial surface grid is refined by bisection refinement to the desired resolution.The final step is to find the triangular element index on the particle triangular surface grid,which contains the projective point.Test cases show that the present mapping algorithm has good accuracy and efficiency for calculating hydrodynamic forces of particles.展开更多
文摘格理论最初是作为一种密码分析工具被引入到密码学中的,用于分析背包密码体制、RSA密码体制等.在1997年,Ajtai和Dwork第一次构造了一个基于格的密码体制Ajtai-Dwork,随后在1998年出现了NTRU密码体制.当时基于整数分解及离散对数的公钥密码体制是主流,格密码一直没有得到足够的重视.直到2009年,Gentry基于格密码构造了首个全同态密码方案,格密码才得到了广泛的发展.2015年,Peikert在"格密码十年"一文中,对之前格密码的发展做了一个很好的总结.同在2015年,美国国家标准和技术研究院(National Institute of Standards and Technology,NIST)发布了"后量子密码报告",报告指出:由于量子计算技术的飞速发展,现有的公钥密码标准在量子计算下将不再安全.同时NIST在全球范围内展开了后量子密码算法标准的征集工作.格密码作为一类经典的抗量子密码,公认是后量子密码算法标准最有力的竞争者,近2年得到了飞速的发展,出现了许多优秀的研究成果.从基于格的零知识证明、格加密、格签名以及格密钥交换4个方面,对近2年格密码研究进行了总结,并对格密码的发展趋势进行了展望.
文摘随着移动计算和物联网等新兴技术的飞速发展,基于位置的服务(Location Based Service,LBS)在人们日常生活中扮演着愈发重要的角色。许多应用(如移动交友)通过LBS获取、收集用户的精确位置,并通过执行距离计算来实现近距离用户发现等功能。然而,LBS在为用户带来便利的同时,也使其面临着泄露隐私位置信息的风险。目前,大多数LBS应用均以明文形式记录用户精确位置,极易泄露用户的位置和移动模式等信息。此外,现有的能够保护用户隐私位置数据的研究工作存在一些缺陷,如通信开销高、通信时间长或计算安全性不足等。因此,文章提出一种保护用户位置隐私的高效近邻检测方法,该方法基于B/FV(Brakerski/Fan-Vercauteren)同态加密构造优化的圆范围内的隐私保护近邻检测协议。与现有的工作相比,文章方案使用基于格的加密,且具有较优的通信性能。此外,文章实现了基于B/FV同态加密的方案原型系统,并给出在具有高隐私保护要求和低算术速度限制的场景中的潜在应用,通过对该原型系统的实验结果表明,该方案在实际部署应用中具有广阔的应用前景。
基金financially supported by the National Natural Science Foundation of China(No.41574127 and 41174104)the National Key Technology R&D Program for the 13th five-year plan(No.2016ZX05018006-006)
文摘To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direct current method, we propose a new mesh refinement and recoarsement method for a two-dimensional point source. We introduce the mesh refinement and mesh recoarsement into the traditional structured mesh subdivision. By refining the horizontal grids, the singularity owing to the point source is minimized and the topography is simulated. By recoarsening the horizontal grids, the number of grid cells is reduced significantly and computational efficiency is improved. Model tests show that the proposed method solves the singularity problem and reduces the number of grid cells by 80% compared to the uniform grid refinement.
文摘A complete mesh free adaptive algorithm （MFAA）, with solution adaptation and geometric adaptation, is developed to improve the resolution of flow features and to replace traditional global refinement techniques in structured grids. Unnecessary redundant points and elements are avoided by using the mesh free local clouds refinement technology in shock influencing regions and regions near large curvature places on the boundary. Inviscid compressible flows over NACA0012 and RAE2822 airfoils are computed. Finally numerical results validate the accuracy of the above method.
基金supported by the 973 Program of China 2005CB321702China NSF 10531080.
文摘Local mesh refinement is one of the key steps in the implementations of adaptive finite element methods. This paper presents a parallel algorithm for distributed memory parallel computers for adaptive local refinement of tetrahedral meshes using bisection. This algorithm is used in PHG, Parallel Hierarchical Grid Chttp：//lsec. cc. ac. cn/phg/）, a toolbox under active development for parallel adaptive finite element solutions of partial differential equations. The algorithm proposed is characterized by allowing simukaneous refinement of submeshes to arbitrary levels before synchronization between submeshes and without the need of a central coordinator process for managing new vertices. Using the concept of canonical refinement, a simple proof of the independence of the resulting mesh on the mesh partitioning is given, which is useful in better understanding the behaviour of the biseetioning refinement procedure.
基金supported by the National Natural Science Foundation of China (No.61370203)China Postdoctoral Science Foundation Funded Project (No.2017M623008)+1 种基金Scientific Research Starting Project of SWPU (No.2017QHZ023)State Scholarship Foundation of China Scholarship Council (No.201708515149)
文摘Public key encryption scheme with keyword search （PEKS） enables us to search the encrypted data in a cloud server with a keyword, and no one can obtain any infor- mation about the encrypted data without the trapdoor corresponding to the keyword. The PEKS is useful to keep the management of large data storages secure such as those in a cloud. In this paper, to protect against quantum computer attacks, we present a lattice-based identity-based encryption scheme with key- word search. We have proved that our scheme can achieve ciphertext indistinguishability in the random oracle model, and our scheme can also achieve trapdoor security. In particular, our scheme can designate a unique tester to test and return the search results, therefore it does not need a secure channel. To the best of our knowledge, our scheme is the first iden- tity-based encryption scheme with keyword search from lattice assumption.
基金supported by the National Natural Science Foundation of China under Grants No.61003262,No.60873237,No.61100205,No.60873001the Fundamental Research Funds for the Central Universities under Grant No.2009RC0212
文摘Security analysis of cryptographic protocols has been widely studied for many years.As far as we know,we have not found any methods to effectively analyze group key exchange protocols for the three parties yet,which did not sacrifice the soundness of cryptography.Recently,Canetti and Herzog have proposed Universally Composable Symbolic Analysis(UCSA) of two-party mutual authentication and key exchange protocol which is based on the symmetric encryption schemes.This scheme can analyze the protocols automatically and guarantee the soundness of cryptography.Therefore,we discuss group key exchange protocol which is based on Joux Tripartite Diffie-Hellman(JTDH) using UCSA.Our contribution is analyzing group key exchange protocol effectively without damaging the soundness of cryptography.
基金supported by the National Natural Science Foundation of China under Grant(No.61772085),(No.61672109),(No.1472024)and.(No.61532012)
文摘In the era of big data, government, business and personal digital information will be possible for data mining. Data mining requires massive data as a support. However, the direct release of the original mass data, which usually contain some sensitive information of personal or analysis, will result in leakage of user privacy. Therefore, it is becoming increasingly important to protect privacy information in data publishing. In this paper, we focus on the multi-type self-identified format-preserving encryption. First, we introduce a multi-type self-identified format-preserving encryption system and discuss the encryption of various types of data in this system. Then, for the format preserving encryption(FPE) about Chinese name, we study from the encryption model construction and basic encryption scheme. The format-preserving encryption model about Chinese name is constructed and the concept of the name library is presented. Based on this, it is used to not only limit the message space to reduce complexity, but also ensure the cipher in accordance with the Chinese naming habits. In addition, according to the encryption and decryption model, format-preserving encryption process of Chinese name is designed. In order to add new names, the algorithm of name space expansion is proposed. Based on the Prefix, this paper put forward an algorithm named Cycle-Prefix, which enhances the security and dynamics of FPE by using two adjustment factors and the circular encryption. Compared with the traditional Prefix algorithm, experiments show that Cycle-Prefix can not only complete the task of FPE for Chinese name, but also encrypt same plain text into different ciphers under the premise of similar efficiency with Prefix.
基金Supported by the National Nature Science Foundation of China（ No. 60773003,60970120）.
文摘Based on the relationship between cheating immune secret sharing and cryptographic criteria of Boolean functions, to design a cheating immune secret sharing scheme, a 1-resilient function satisfying the strict avalanche criterion （SAC） is needed. In this paper, a technique on constructing a cheating immune secret sharing function is studied. By using Maiorana-McFarland construction technique, two new methods to construct cheating immune secret sharing functions are proposed.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 90203008 and 10547120 and the Doctoral Foundation of the Ministry of Education of China under Grant No. 2002055009
文摘We present a self-synchronizing stream encryption scheme based on one-dimensional coupled map lattices which is introduced as a model with the essential features of spatiotemporal chaos, and of great complexity and diffusion capability of the little disturbance in the initial condition. To evaluate the scheme, a series of statistical tests are employed, and the results show good random-look nature of the ciphertext. Furthermore, we apply our algorithm to encrypt a grey-scale image to show the key sensitivity.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51636009 and 52006212)Chinese Academy of Sciences(Grant Nos.ZDBS-LY-JSC033 and XDB22040201).
文摘Immersed boundary method is a crucial method to deal with particle suspension flow.Particle shapes involved in such flow are usually simple geometry,such as sphere and ellipsoid,which can be conveniently represented by the triangular surface grid.When the number of particles and resolution of the surface grid increase,calculating the hydrodynamic force on the particle surface through integration can be time-consuming.Hence,the present paper establishes a fast mapping method to evaluate immersed boundary hydrodynamic force.Firstly,the particle surface grid is generated by an initial triangular element grid.Subsequently,the initial surface grid is refined by bisection refinement to the desired resolution.The final step is to find the triangular element index on the particle triangular surface grid,which contains the projective point.Test cases show that the present mapping algorithm has good accuracy and efficiency for calculating hydrodynamic forces of particles.
