基于特征值的无可信中心的秘密共享方案研究

利用矩阵特征值的特性,该文提出新的无可信中心的秘密共享方案。该方案无需可信中心的参与,每个参与者提供相同的秘密份额(列向量),在黑盒子中协同产生各自的秘密份额,从而避免可信中心的权威欺骗。所有参与者提供的列向量组成一个可逆矩阵 P ,可逆矩阵 P 和对角矩阵${Λ}$生成一个矩阵 M ,并将该矩阵正交化的单位特征向量,作为子密钥分发给各参与者。由于同一个集合的参与者所对应的特征值是相同的,该方案可以有效地防止成员之间的恶意欺诈行为。分析结果表明,该方案是可行的、安全的。     

基于矢量共享方案的数字水印分存算法

提出一种基于矢量共享方案的数字水印算法,将矢量共享的思想用于数字水印.算法在对水印信息隐藏前,对原始水印和分块水印都进行扰乱处理,同时分存也具有加密作用,算法具有很高的安全性.实验表明,算法还具有很好的隐藏效果和抗剪切功能.     

一种新的理性秘密共享方案

In this paper, we propose a new approach for rational secret sharing in game theoretic settings. The trusted center is eliminated in the secret reconstruction phase. Every player doesn’t know current round is real round or fake round. The gain of following the protocol is more than the gain of deviating, so rational player has an incentive to abide the protocol. Finally, every player can obtain the secret fairly. Our scheme is verifiable and any player’s cheating can not work. Furthermore the proposed scheme is immune to backward induction and satisfies resilient equilibrium. No player of the coalition C can do better, even if the whole coalition C cheats.Our scheme can withstand the conspiracy attack with at most m-1 players.     

Hypergraph decomposition and secret sharing

A secret sharing scheme is a protocol by which a dealer distributes a secret among a set of participants in such a way that only qualified sets of them can reconstruct the value of the secret whereas any non-qualified subset of participants obtain no information at all about the value of the secret. Secret sharing schemes have always played a very important role for cryptographic applications and in the construction of higher level cryptographic primitives and protocols.In this paper we investigate the construction of efficient secret sharing schemes by using a technique called hypergraph decomposition, extending in a non-trivial way the previously studied graph decomposition techniques. A major advantage of hypergraph decomposition is that it applies to any access structure, rather than only structures representable as graphs. As a consequence, the application of this technique allows us to obtain secret sharing schemes for several classes of access structures (such as hyperpaths, hypercycles, hyperstars and acyclic hypergraphs) with improved efficiency over previous results. Specifically, for these access structures, we present secret sharing schemes that achieve optimal information rate. Moreover, with respect to the average information rate, our schemes improve on previously known ones.In the course of the formulation of the hypergraph decomposition technique, we also obtain an elementary characterization of the ideal access structures among the hyperstars, which is of independent interest.     

Bounds for visual cryptography schemes

In this paper, we investigate the best pixel expansion of various models of visual cryptography schemes. In this regard, we consider visual cryptography schemes introduced by Tzeng and Hu (2002) [13]. In such a model, only minimal qualified sets can recover the secret image and the recovered secret image can be darker or lighter than the background. Blundo et al. (2006) [4] introduced a lower bound for the best pixel expansion of this scheme in terms of minimal qualified sets. We present another lower bound for the best pixel expansion of the scheme. As a corollary, we introduce a lower bound, based on an induced matching of hypergraph of qualified sets, for the best pixel expansion of the aforementioned model and the traditional model of visual cryptography scheme realized by basis matrices. Finally, we study access structures based on graphs and we present an upper bound for the smallest pixel expansion in terms of strong chromatic index.     

Two-layered structure for optimally essential secret image sharing scheme

This paper presents a two-layered structure for optimally sharing a secret image among s essential and n − s non-essential shared shadows using the (t, s, k, n) essential thresholds, that t essential shared shadows and totally k shared shadows are needed to recover the secret image. The presented two-layered structure includes one user-defined parameter m to determine different kinds of optimal results. m = 1 leads to minimum size of total shared shadows (ST) and size of an essential shared shadow is close to size of a non-essential shared shadow. On the other hand, m = t leads to size of an essential shared shadow being twice of size of a non-essential shared shadow to signify the importance of an essential shared shadow. Moreover, the proposed structure overcomes the threshold fulfillment problem in Chen’s scheme (Chen, 2016). Theoretical analyses and experimental results show that the proposed scheme exhibits secure with optimal sharing ratios among related works.     

一种新的密钥分割门限方案及密钥托管体制

密钥托管密码体制不仅能保护用户的隐私权，同时允许法律授权下的监听，本文首先提出了一种新的秘密分割门限方案，然后基于这种新的秘密分割门限方案，提出了一种分割密钥托管体制，并分析了体制的安全性。     

SECURE GROUP COMMUNICATIONS FOR LARGE DYNAMIC MULTICAST GROUP

As the major problem in multicast security, the group key management has been the focus of research. But few results are satisfactory. In this paper, the problems of group key management and access control for large dynamic multicast group have been researched and a solution based on SubGroup Secure Controllers (SGSCs) is presented, which selves many problems in IOLUS system and WGL scheme.     

The volume and foundation of star trades

An x-star trade consists of two disjoint decompositions of some simple graph H into copies of K_1,x, the graph known as the x-star. The number of vertices of H is referred to as the foundation of the trade, while the number of copies of K_1,x in each of the decompositions is called the volume of the trade. We determine all values of x, v and s for which there exists a K_1,x-trade of volume s and foundation v.