基于二次剩余的密钥体制的构造

为了避免确定性的公钥密码体制容易遭受选择明文攻击的问题,文中以大数因数分解的困难性和模Blum数的二次剩余求平方根的不易性为理论基础,引入随机数,构造了一种以二次剩余为基础的多项式加密密钥体制。该密码体制的密码强度不低于RSA公钥密码体制的密码强度,可以有效地抵挡来自选择明文的攻击,安全性较高。它的密文膨胀率不高于Blum和Goldwasser提出的BG密码体制的密文膨胀率,当我们要传输的明文较长时,它的密文膨胀率近似为1。     

基于二维Logistic映射和二次剩余的图像加密算法

针对公共网络中数字图像的安全传播问题,提出了一种基于二维Logistic混沌映射和二次剩余的图像加密算法.该加密算法利用二维Logistic映射的优良随机性,对明文图像进行2次置乱,极大地改变了图像像素位置.然后把置乱图像展开成二进制序列,按照8位一组进行分块,再利用二次剩余密码体制对每个分块进行加密,有效地改变了明文图像的信息.最后,对该算法进行直方图分析、信息熵分析、密钥敏感性分析以及明文图像和密文图像的相关系数分析等仿真实验.实验表明该算法能抵抗统计攻击、信息熵攻击,是一种较安全的图像通信方式.     

基于二维Logistic映射和二次剩余的图像加密算法

针对公共网络中数字图像的安全传播问题,提出了一种基于二维Logistic混沌映射和二次剩余的图像加密算法.该加密算法利用二维Logistic映射的优良随机性,对明文图像进行2次置乱,极大地改变了图像像素位置.然后把置乱图像展开成二进制序列,按照8位一组进行分块,再利用二次剩余密码体制对每个分块进行加密,有效地改变了明文图像的信息.最后,对该算法进行直方图分析、信息熵分析、密钥敏感性分析以及明文图像和密文图像的相关系数分析等仿真实验.实验表明该算法能抵抗统计攻击、信息熵攻击,是一种较安全的图像通信方式.     

抗合谋攻击的多变量群签名方案

多变量公钥密码体制能抵御量子计算机的攻击,被认为是后量子时代的一种安全的密码体制备选方案.提出了一种基于多变量公钥密码体制的群签名设计模型,同时在分析该方案时,提出了一种合谋攻击方案,可以有若干合谋攻击者对群签名体制进行伪造签名攻击.随后,给出了一种新的矩阵乘法定义,以及素矩阵等概念,并提出了一种可以抵抗合谋攻击的基于多变量公钥密码体制的群签名设计模型.分析结果表明:该方案不仅能够从根本上抵抗合谋攻击和伪造签名攻击,而且在保证匿名性的前提下,能够真正实现签名成员身份的可追查性,同时通过构造安全的密钥生成协议保证群签名私钥的不可知性,因此具有更高的安全性.     

一种改进的中间域多变量公钥签名方案

多变量公钥密码体制能抵抗量子计算机的攻击,被认为是后量子时代一种安全的密码体制备选方案.考虑到原中间域多变量公钥加密体制不能抵抗高阶线性化攻击,利用一种新的外部干扰,重构中心映射,提出一种基于外部干扰的改进签名方案.改进方案保持了原方案结构简单、求逆容易的性质,还能抵抗穷举攻击,秩攻击,差分攻击,代数攻击.     

一种新的公钥密码体制和签名方案

文章提出一种新的安全性基于离散对数难题的公钥密码体制,以及安全性基于大整数分解难题的签名方案.与BSA体制和ELGAMAL体制相比,该密码体制能抵抗通过将一个密文表示成其他已知明文的密文的幂乘来求得该密文所对应的明文的攻击,该签名方案能抵抗通过已知的消息-签名对相除得到某些消息的签名的攻击,同时该密码体制和签名方案不需要使用随机数生成器生成加密参数,也不需要避免该参数的重复使用.在对该密码体制和签名方案进行分析后,得出该密码体制和签名方案是安全的.     

基于LWE问题构造密码方案综述

在后量子密码时代,如何设计可以抵抗量子计算攻击的密码体制是后量子密码的主要任务,基于格的公钥密码体制被认为是最有可能抵御量子威胁的密码体制之一,基于容错学习(learning with errors, LWE)问题构建的密码体制是基于格密码发展实用前景最好的两种构建方案之一。从基于LWE问题构建基于属性加密方案、全同态加密方案、函数加密方案、密钥交换协议、数字签名方案等5个方面,对基于LWE问题构造的密码方案和当前研究面临的挑战进行了总结。     

可证安全的常数长度无证书聚合签名方案

针对无证书密码体制可以解决基于身份的公钥密码体制的密钥托管问题和基于证书的公钥密码体制的公钥认证问题,构造了无证书聚合签名的可证明安全模型,并提出了一个具体的签名长度与人数无关的聚合签名方案.基于计算性Diffie Hellman难题,在随机预言模型下,证明了提出的方案可以抵抗适应性选择消息和身份的存在性伪造攻击.     

丢番图—背包型公开钥密码体制

本文基于背包型公开钥密码体制建立丁一种新的公开钥密码体制。其安全性在一定程度上取决于NP—C问题——丢番图方程整数解的判定问题,从而避免了低密度的攻击。而其加、解密速度仍继承了背包体制运行速度快的优点。     

基于椭圆密码体制的移动通信网门限托管方案

本文给出了一种新的基于椭圆密码体制、适合在移动通信网中使用的门限(t．m)密钥托管方案：在m个托管代理中。有若干个不愿合作或无法合作而剩余的t个托管代理能够正常合作的情况下，合法的监听机构仍然能重构出会话密钥。本方案能够在保证移动用户安全通信的同时．使合法监听机构对用户通信进行实时监听。本方案解决了密钥托管中“一次监听，永久监听”的问题，具有防欺诈、抵抗LEAF反馈攻击的特性。     

基于多变量公钥密码体制的环签名方案

环签名可以让用户完全匿名地对消息进行签名.迄今为止所有的环签名都基于传统密码体制.然而随着量子计算机的出现,传统密码体制的安全性受到威胁.多变量公钥密码学是一种高效的密码体制,并且有可能成为后量子时代安全的密码体制.提出了一个基于多变量公钥密码体制的环签名方案,该方案满足无条件匿名性,在非适应性选择消息下满足不可为造性,且运算效率高.     

New Public Key Cryptosystems from Combinatorial Group Theory

0 IntroductionThe security of most commonly used cryptographicschemesis essentially based onthree families of compu-tational problems :the integer factoring problem(RSAprob-lem) ,the Diffie-Hell man problemand the discrete logarithmproblem,andthe elliptic curve variants thereof .Inthe middleof 1990s , Shor[1], Bonehet al[2]presented some remarkablequantumalgorithms which can solveinteger factoring problemand discrete logarithmproblemover any group including Ga-lois fields and elliptic curve…     

A Generic Solution to Realize Public Verifiability of Signcryption

0 IntroductionIn 1997 , Zheng[1]proposed a new pri mitive called sign-cryption, which si multaneously provides authenticity andconfidentiality within a single logic step.Signcryptionis moreefficient than the conventional“sign-then-encrypt”approach.Many signcryption schemes[2-5]have been proposed so far .For more details about the development of signcryption we re-fer the readers to Ref .[6] .Asecure signcryptionscheme should satisfy public verifi-ability (including non-repudiation)[1]. Wef…     

用丢番图方程构作公开钥密码

运用多元k次(k是奇数)丢番图方程构造了一类陷门单向函数,用它们可以建立一种新的公开钥密码.由于多元高次丢番图方程求解的困难性,这样密码更具有安全性.     

New Public-Key Cryptosystem Based on the Morphism of Polynomials Problem

During the last two decades, there has been intensive and fast development in Multivariate Public Key Cryptography(MPKC), which is considered to be an important candidate for post-quantum cryptography. However,it is universally regarded as a difficult task, as in the Knapsack cryptosystems, to design a secure MPKC scheme(especially an encryption scheme) employing the existing trapdoor construction. In this paper, we propose a new key-exchange scheme and an MPKC scheme based on the Morphism of Polynomials(MP) problem. The security of the proposed schemes is provably reducible to the conjectured intractability of a new difficult problem,namely the Decisional Multivariate Diffie-Hellman(DMDH) problem derived from the MP problem. The proposed key agreement is one of several non-number-theory-based protocols, and is a candidate for use in the post-quantum era. More importantly, by slightly modifying the protocol, we offer an original approach to designing a secure MPKC scheme. Furthermore, the proposed encryption scheme achieves a good tradeoff between security and efficiency,and seems competitive with traditional MPKC schemes.     

An Efficient and Practical Public Key Cryptosystem with CCA-Security on Standard Model

Chosen Ciphertext Attack （CCA） security on the standard model is widely accepted as the standard security notion for the public key cryptosystem. The existing CCA-secure public key cryptosystems on the standard model are expensive in terms of efficiency and practicality. In this paper, an efficient and practical public key cryptosystem is presented over the group of signed quadratic residues. It is provably secure against CCA on the standard model. Furthermore, public verifiability for this scheme is also realized in the way that projects the verification privacy key into public key on trapdoor pretending. It will be useful to devise efficient CCA-secure threshold and proxy re-encryption schemes on the standard model.     

背包公钥密码系统的安全性与设计

本文讨论了一般背包公钥密码系统的位安全性问题，建立了这种系统中原文整体和某些特定位的安全性的等价关系。提出了一个新的基于背包问题的公钥系统，且不涉及任何背包分量超递增序列，与Merkle-Hellman系统有着本质的区别。此外，适当选择参数时，系统密度可达很高。因而，现有的Shamir的破译算法和Brickell解低密度背包问题的算法对该系统均无效。     

Cryptanalysis of schemes based on pseudoinverse matrix

Advances in quantum computation threaten to break public key cryptosystems that are based on the difficulty of factorization or the difficulty of discrete logariths, although, no quantum algorithms have been found to be able to solve certain mathematical problems on non-commutative algebraic structures up to now. The proposed new quasi-inverse based cryptography scheme is vulnerable to a linear algebra attack based on the probable occurrence of weak keys in the generation process. In this paper, we illustrate that two of the quasi-inverse based cryptography are vulnerable to a structural attack and that it only requires polynomial time to obtain the equivalent keys for some given public keys. In addition, we conduct a detailed analysis on attack methods and provide some improved suggestions on these two schemes.     

Efficient Identity Based Signcryption Scheme with Public Verifiability and Forward Security

In this paper, we point out that Libert and Quisquater‘s signeryption scheme cannot provide public verifiability. Then we present a new identity based signcryption scheme using quadratic residue and pairings over elliptic curves. It combines the functionalities of both public verifiability and forward security at the same time. Under the Bilinear Diffie-Hellman and quadratic residue assumption, we describe the new scheme that is more secure and can be some what more efficient than Libert and Quisquater‘s one.