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1.
基于MSP秘密共享的(t,n)门限群签名方案 总被引:1,自引:0,他引:1
门限群签名是群签名中重要的—类,它是秘钥共享与群签名的有机结合.本文通过文献[5]中的MSP方案(Monotone Span Program),提出了一种新的门限群签名方案.在本签名方案建立后,只有达到门限的群成员的联合才能生成—个有效的群签名,并且可以方便的加入或删除成员.一旦发生争议,只有群管理员才能确定签名人的身份.该方案能够抵抗合谋攻击:即群中任意一组成员合谋都无法恢复群秘钥k.本方案的安全性基于Gap Diffie-Hellman群上的计算Diffie-Hellmanl可题难解上,因此在计算上是最安全的. 相似文献
2.
环签名是一种特殊的数字签名,可以广泛应用于电子选举、移动通信、移动代理、电子商务等领域.提出了一种新的基于格的环签名方案,在格上的小整数解和非齐次小整数解困难问题的假设下,方案对适应性选择消息攻击是强不可伪造的.利用的格基代理技术,可以保证新方案签名长度更短,计算效率更高. 相似文献
3.
基于有限域上离散对数难解问题和强RSA假设,提出了一个前向安全的指定验证人代理多重签名方案.在方案中,代理签名人不仅可以代表多个原始签名人生成指定验证人的代理多重签名,确保只有原始签名人指定的验证人可以验证代理多重签名的有效性;而且在该方案中,代理多重签名是前向安全的,即使代理签名人当前时段的代理多重签名密钥被泄漏,敌手也不能伪造此时段之前的代理多重签名,以前所产生的代理多重签名依然有效. 相似文献
4.
代理环签名是一种特殊的数字签名,可以广泛地应用于很多生活领域.但是现有的代理环签名方案的安全性大都是在随机预言模型下证明的,在实际应用中不一定安全.提出一个标准模型下基于格的代理环签名方案,同时,基于格上的难题SIS和ISIS,证明了方案能够抵抗存在性伪造攻击. 相似文献
5.
在给出块共轭概念的基础上,提出了适合并行计算的向量组的块共轭化方法,进而得到解无约束最优化问题的并行块共轭方向法.有大量数值结果表明块共轭方向法具有工作量少.适用函数范围广等特点,是一种比较有效的无约束最优化方法. 相似文献
6.
超可解群的若干充分条件 总被引:9,自引:0,他引:9
本文研究了有限群的超可解性问题,利用子群的共轭可换性概念及极小反例法,获得了一个群为超可解的若干充分条件.举例说明了主要结果中的假设条件是不可少的. 相似文献
7.
《数学的实践与认识》2015,(7)
基于证书的密码体制既能降低公钥的管理费用又能解决密钥托管问题,代理签名可以让一个原始签名者在自己不方便亲自签名的情况下,委托他信任的代理人代替他签名.针对目前基于证书的代理签名方案普遍基于双线性对来实现因而效率不高和其安全模型不完善的问题,给出了新的基于证书的代理签名的安全模型,并提出一个不使用双线性对的基于证书的代理签名方案.在随机预言机模型中,基于椭圆曲线离散对数问题假设,对方案进行了不可伪造性的证明.最后,对方案的效率进行了比较,结果表明方案是高效的. 相似文献
8.
梯度投影法是一类有效的约束最优化算法,在最优化领域中占有重要的地位.但是,梯度投影法所采用的投影是正交投影,不包含目标函数和约束函数的二阶导数信息·因而;收敛速度不太令人满意.本文介绍一种共轭投影概念,利用共轭投影构造了一般线性或非线性约束下的共轭投影变尺度算法,并证明了算法在一定条件下具有全局收敛性.由于算法中的共轭投影恰当地包含了目标函数和约束函数的二阶导数信息,因而收敛速度有希望加快.数值试验的结果表明算法是有效的. 相似文献
9.
本文研究与Hopf代数H关联之YeterDrinfel’d范畴YHD中的辫化余交换余代数C,证明HYD中左C-余模范畴HYD是张量范畴,且HYD中辫结构Ψ诱导CHYD中一辫结构当且仅当对CHDY中任意对象N有ΨN,CΨC,NCΓN=CYDΓN;由此导致新的辫化张量范畴. 相似文献
10.
11.
Braid cryptosystem was proposed in CRYPTO 2000 as an alternate public-key cryptosystem. The security of this system is based
upon the conjugacy problem in braid groups. Since then, there have been several attempts to break the braid cryptosystem by
solving the conjugacy problem in braid groups. In this article, we first survey all the major attacks on the braid cryptosystem
and conclude that the attacks were successful because the current ways of random key generation almost always result in weaker
instances of the conjugacy problem. We then propose several alternate ways of generating hard instances of the conjugacy problem
for use braid cryptography.
相似文献
12.
The cycling operation is a special kind of conjugation that can be applied to elements in Artin’s braid groups, in order to reduce their length. It is a key ingredient of the usual solutions to the conjugacy problem in braid groups. In their seminal paper on braid-cryptography, Ko, Lee et al. proposed the cycling problem as a hard problem in braid groups that could be interesting for cryptography. In this paper we give a polynomial solution to that problem, mainly by showing that cycling is surjective, and using a result by Maffre which shows that pre-images under cycling can be computed fast. This result also holds in every Artin-Tits group of spherical type, endowed with the Artin Garside structure.On the other hand, the conjugacy search problem in braid groups is usually solved by computing some finite sets called (left) ultra summit sets (left-USSs), using left normal forms of braids. But one can equally use right normal forms and compute right-USSs. Hard instances of the conjugacy search problem correspond to elements having big (left and right) USSs. One may think that even if some element has a big left-USS, it could possibly have a small right-USS. We show that this is not the case in the important particular case of rigid braids. More precisely, we show that the left-USS and the right-USS of a given rigid braid determine isomorphic graphs, with the arrows reversed, the isomorphism being defined using iterated cycling. We conjecture that the same is true for every element, not necessarily rigid, in braid groups and Artin-Tits groups of spherical type. 相似文献
13.
《代数通讯》2013,41(3):1021-1039
Small Gaussian groups are a natural generalization of spherical Artin groups, namely groups of fractions of monoids in which the existence of least common multiples is kept as an hypothesis, but the relations between the generators are not supposed to necessarily be of Coxeter type. We show here how to extend the Elrifai–Morton solution for the conjugacy problem in braid groups to every small Gaussian group. 相似文献
14.
The recent proof by Bigelow and Krammer that the braid groups are linear opens the possibility of applications to the study
of knots and links. It was proved by the first author and Menasco that any closed braid representative of the unknot can be
systematically simplified to a round planar circle by a finite sequence of exchange moves and reducing moves. In this paper
we establish connections between the faithfulness of the Krammer-Lawrence representation and the problem of recognizing when
the conjugacy class of a closed braid admits an exchange move or a reducing move. 相似文献
15.
Samuel Maffre 《Designs, Codes and Cryptography》2006,39(3):347-373
This work emphasizes an important problem of braid based cryptography: the random generation of good keys. We present a deterministic,
polynomial algorithm that reduces the conjugacy search problem in braid group. The algorithm is based on the decomposition
of braids into products of canonical factors and gives a partial factorization of the secret: a divisor and a multiple. The
tests we performed on different keys of existing protocols showed that many protocols in their current form are broken and
that the efficiency of our attack depends on the random generator used to create the key. Therefore, this method gives new
critera for testing weak keys. We also propose a new random generator of key which is secure against our attack and the one
of Hofheinz and Steinwandt. 相似文献
16.
L.A. Bokut 《Journal of Algebra》2009,321(2):361-376
In this paper, we obtain Gröbner–Shirshov (non-commutative Gröbner) bases for braid groups in the Birman–Ko–Lee generators enriched by “Garside word” δ [J. Birman, K.H. Ko, S.J. Lee, A new approach to the word and conjugacy problems for the braid groups, Adv. Math. 139 (1998) 322–353]. It gives a new algorithm for getting the Birman–Ko–Lee normal forms in braid groups, and thus a new algorithm for solving the word problem in these groups. 相似文献
17.
Andrew Sale 《代数通讯》2013,41(2):873-897
Determining the length of short conjugators in a group can be considered as an effective version of the conjugacy problem. The conjugacy length function provides a measure for these lengths. We study the behavior of conjugacy length functions under group extensions, introducing the twisted and restricted conjugacy length functions. We apply these results to show that certain abelian-by-cyclic groups have linear conjugacy length function and certain semidirect products ?d ? ?k have at most exponential (if k > 1) or linear (if k = 1) conjugacy length functions. 相似文献
18.
The main objective of the paper is the proof of the unsolvability of the conjugacy problem for subgroups of the pure braid
groupR
5.
Translated fromMatematicheskie Zametki, Vol. 65, No. 1, pp. 15–22, January, 1999. 相似文献
19.
In this note we solve the twisted conjugacy problem for braid groups, i.e., we propose an algorithm which, given two braids u, υ ∈ B n and an automorphism φ ∈ Aut(B n ), decides whether υ = (φ(x))?1 ux for some x ∈ B n . As a corollary, we deduce that each group of the form B n ? H, a semidirect product of the braid group B n by a torsion-free hyperbolic group H, has solvable conjugacy problem. 相似文献
20.