两种新的彩色图像(n, n)分存方案

提出了两种彩色图像的（n,n）．分存方案，解密过程仅需要执行XOR运算。这两种方案重构密图的复杂度与可视分存方案等价，更为重要的是该方案没有像素膨胀，并且重构密图的质量优于彩色可视分存方案。     

多分存彩色图像秘密共享（2，n）方案

文献[2]中提出了一种基于异或（XOR）操作的彩色图像秘密共享（2,n）方案,简单易于实现,但恢复密图的效果较差。通过分析此方案,文章提出一个多分存的彩色图像秘密共享（2,n）方案,通过给用户增加分存图像的方法改善了恢复密图的质量。实验分析表明所提方案不仅取得了很好的恢复效果,而且保持了安全性和算法的简单性。     

关于(k,n)-门限方案的进一步讨论

1979年,Shamir提出的(k,n)-门限密钥分散管理的概念使密钥管理更加安全灵活,但这一方案也有其不完善之处,因为在现实中参与密钥管理的人在系统中所处的地位不尽相同,有许多活动要求某些特定的人必须参与才能进行。本文考查了此类情形,将(k,n)-门限方案加以推广,提出了更为一般的(t,k,n)-门限方案,并利用(k,n)-门限方案给出了实现(t,k,n)-门限方案的方法。     

基于分存分组的关系数据库数字水印算法

文章结合关系数据库的特殊性,提出了一种基于分存分组的数据库数字水印算法,通过该算法可以在关系数据库中嵌入实际意义的字符串水印信息。首先把水印信息进行加密,让版权所有者和公证方持有加密密钥,然后将加密的水印信息分存,最后将水印分存值分成比特不等组序列进行水印嵌入。在水印提取时,可以通过部分子水印信息恢复原始水印。实验结果表明该算法使嵌入的水印具有较好的鲁棒性和不可见性。     

一种新的阈值可视密钥分存方案 黄东平

本文提出(k,n)阈值可视秘密分存的一种新的分析和实现方案.该方案从可视分存的对比度条件和安全性条件入手,建立起一个方程组,最后得到其近似最优解和基本矩阵的构造方案.该方案将(k,n)和(n,n)方案统一起来分析,使之和谐统一;同时,通过理论分析代替了以往算法的部分工作;本文给出的算法可达到以往方案的安全强度而具备更高的实现效率.     

具有掩盖图像的（2，2）可视密码方案

为解决传统可视密码像素膨胀及分存图像无意义等问题,文中提出了一个具有掩盖图像的（2,2）可视密码方案。方案中密图为黑白反色图像,利用半色调技术将两个灰度图像处理后的半色调图像作为掩盖图像,根据密图修改掩盖图像生成分存图像,叠加分存图像恢复密图。方案符合可视密码解密简单的特性且分存图像有意义,没有引入任何像素膨胀。     

基于挑战-应答机制的量子密钥分发协议

基于BB84协议,利用挑战-应答机制,提出了一种量子密钥分发协议。发送方Alice和接收方Bob通过安全信道共享三个不同的Hash函数( , 和 ),以及随机比特串 。在每次密钥分发时,Alice产生随机比特串 （挑战信息）和 （密钥）,结合 和 ,基于BB84协议产生光子串 ;Alice将 和 发送给Bob,Bob接收到对应的 和光子串 ;Bob利用 ,结合 和 ,基于BB84协议对光子串 进行测量得到 。理想情况下共享密钥 。另外,Bob利用 , , 及 产生应答序列 ;Alice和Bob利用各自拥有的序列及 分别产生序列 和 ,并对各自的 做更新。在密钥分发过程中光子的利用率为百分百,该协议既有BB84协议类似的安全性,又有单向身份认证功能。     

d维(t,n)门限量子同态加密算法的设计与仿真

量子同态加密对量子态密文直接进行同态评估计算,而不是将密文解密之后再进行计算.基于相位和状态变换的d维通用酉算子,提出了一种d维（t,n）门限量子同态加密算法.在该算法中,客户端将量子态密文传送给n个服务器中的t个,这t个服务器生成评估子密钥,运行评估算法对量子态密文执行同态计算.客户端对解密之后的量子态执行CNOT门操作,t+1个粒子的聚合值就是评估算法对量子态明文计算之后的结果.该算法使用Shamir（t,n）门限机制隐藏了评估密钥,保护了客户端的隐私数据.从理论上证明了算法的正确性,各个阶段操作过程的仿真实现进一步验证了算法的正确性.     

ITBES：一种基于门限与身份的WSN加密签名方法

为了提高基于身份的加密签名（IBES）系统中密钥生成中心（PKG）的可信性,采用门限密码学中的（t,n）秘密共享方法,对Xavier IBES算法进行了改进,将主密钥s共享于n个对等的可信第三方PKG之间,并且将改进后的新的基于门限与身份的加密签名一体化方法（ITBES）应用于无线传感器网络,从方法的复杂性、存储需求、安全性方面进行了分析,结果表明我们的方法能够提高PKG可信性,加强无线传感器网络的安全。     

一类多状态连续n中取k(G)系统的可靠性计算

为了计算多状态连续厅中取后（G）系统的可靠性,引入4个定理,将满足引理的多状态系统转换为二元状态系统。分别推导了多状态线形连续k／n（G）系统和环形连续k／n（G）系统的可靠性计算公式。证明了固定k值增加一个新部件,若部件可靠性独立同分布,线形和环形系统可靠性均增加;若部件可靠性独立但不同分布,环形系统存在一个极值,新增加部件可靠性大于这个极值时得到的新系统可靠性增加,反之系统可靠性下降。     

A Novel （n, n） Secret Image Sharing Scheme Based on Sudoku

Recently, Chang et al. proposed a Sudoku-based secret image sharing scheme. They utilized the Sudoku grid to generate meaningful shadow images, and their scheme satisfied all essential requirements. Based on Chang et al.'s scheme, we propose a novel (n, n) secret image sharing scheme based on Sudoku. In the proposed scheme, a secret image can be shared among n different cover images by generating n shadow images, and the secret image can be reconstructed without distortion using only these n shadow images. Also, the proposed scheme can solve the overflow and underflow problems. The experimental results show that the visual quality of the shadow images is satisfactory. Furthermore, the proposed scheme allows for a large embedding capacity.     

多重门限的图像秘密共享方案

 针对传统的基于视觉密码的图像秘密共享方案存在像素扩张导致其只能共享小尺寸的秘密图像、信息隐藏效率较低的问题,提出一种能够提高信息隐藏容量的(t,k,n)多重门限图像秘密共享方案.该方案利用秘密图像信息控制视觉密码方案中共享矩阵的选取,从而实现秘密图像在视觉密码方案中的隐藏.在秘密图像恢复的第一阶段,任意t个参与者直接叠加其影子图像后可以视觉解密出低质量的秘密图像信息;在第二阶段,任意k个参与者可以从影子图像中提取出隐藏的信息,并通过计算恢复出精确的灰度秘密图像.相对于传统的视觉密码方案,本文方案在不影响视觉密码恢复图像的视觉质量前提下,可以隐藏更多的秘密图像信息,而像素扩张尺寸较小.     

一个有效的门限多重秘密共享体制

针对Chien-Jan-Tseng体制计算量大以及Yang-Chang-Hwang体制公开信息量大的不足,利用双变量单向函数提出了一个新的(t,n)门限多重秘密共享体制.通过一次秘密共享过程就可以实现对任意个秘密的共享,而参与者秘密份额的长度仅为一个秘密的长度.在秘密重构过程中,每个合作的参与者只需提交一个由秘密份额计算的伪份额,而不会暴露其秘密份额本身.本文体制结合了现有体制的优点并避免了它们的缺点,是一个实用、有效的体制.     

Efficient multi-secret image sharing based on Boolean operations

(n,n) visual secret sharing (VSS), first proposed by Naor and Shamir (1995) [4], is used to encode (encrypt) a secret image into n meaningless share images to be superimposed later to decode (decrypt) the original secret by human visual system after collecting all n secret images. In recent years, VSS-based image sharing (encryption) and image hiding schemes, two of a variety of applications based on VSS, have drawn much attention. In this paper, an efficient (n+1,n+1) multi-secret image sharing scheme based on Boolean-based VSS is proposed to not only keep the secret images confidential but also increase the capacity of sharing multiple secrets. The Boolean-based VSS technology, used to encode the secret images, generates n random matrices; then the n secret images are subsequently encoded into the n+1 meaningless share images. It is worthwhile to note that n secret images can be hidden by means of sharing only n+1 share images in the proposed scheme instead of 2n share images. Thus, the present scheme thus benefits from (1) reducing the demand of image transmission bandwidth, (2) easing the management overhead of meaningless share images, and (3) involving neither significant extra computational cost nor distortion for reconstructed secret images. The experimental results show the performance in terms of feasibility and image sharing capacity. Applied into image hiding schemes, the proposed scheme can enhance the hiding capacity.     

一种安全有效的（t,n）多秘密共享认证方案

基于双子密钥的思想给出了一种安全有效的(t,n)多秘密共享认证方案,其优点是每个成员可以多次使用自己的子密钥来恢复庄家任意给定的用于共享的多个密钥,重构一个密钥只需公开3个参数,为抵抗成员的欺骗无须执行零知识证明协议.所给的方案与已有的方案相比在计算量和通信量方面有明显的优越性.     

Construction of General (k, n) Probabilistic Visual Cryptography Scheme

Visual cryptography scheme (VCS) is a secure method that encrypts a secret image by subdividing it into shadow images. Due to the nature of encryption VCS is categorized into two types: the deterministic VCS (DVCS) and the probabilistic VCS (PVCS). For the DVCS, we use m (known as the pixel expansion) subpixels to represent a secret pixel. The PVCS uses only one subpixel to represent a secret pixel, while the quality of reconstructed image is degraded. A well-known construction of (k, n)-PVCS is obtained from the (k, n)-DVCS. In this paper, we show another construction of (k, n)-PVCS by extending the (k, k)-PVCS.     

AN EFFICIENT AND SECURE （t, n） THRESHOLD SECRET SHARING SCHEME

Based on Shamir＇s threshold secret sharing scheme and the discrete logarithm problem, a new （t, n） threshold secret sharing scheme is proposed in this paper. In this scheme, each participant＇s secret shadow is selected by the participant himself, and even the secret dealer cannot gain anything about his secret shadow. All the shadows are as short as the shared secret. Each participant can share many secrets with other participants by holding only one shadow. Without extra equations and information designed for verification, each participant is able to check whether another participant provides the true information or not in the recovery phase. Unlike most of the existing schemes, it is unnecessary to maintain a secure channel between each participant and the dealer. Therefore, this scheme is very attractive, especially under the circumstances that there is no secure channel between the dealer and each participant at all. The security of this scheme is based on that of Shamir＇s threshold scheme and the difficulty in solving the discrete logarithm problem. Analyses show that this scheme is a computationally secure and efficient scheme.     

Multi-factor cheating prevention in visual secret sharing by hybrid codebooks

Visual secret sharing, or the so-called visual cryptography, is a well-known scheme that encrypts a secret image into several meaningless share images, usually printed on transparencies, and decrypts as stacking some or all share images by the human visual system. More and more researches about visual secret sharing and its applications have been recently proposed. Unfortunately, the cheating attack in which malicious participants cheat the honest one(s) by forging a fake share image has existed. Since 2006, some cheating prevention schemes have been proposed but suffered from one or more disadvantages as follows: (1) maintaining extra share images used to verify the integrity of a share image prior to stacking, (2) introducing extra pixel expansion, (3) raising heavy computation cost, and (4) giving ambiguous cheating detection. In this paper, a multi-factor cheating–preventing scheme, aiming at exploiting the hybrid codebook to hide the additional verification images into the share images, has been proposed without suffering the above-mentioned deficiencies. Two-factor cheating–detection exploits the design of verification to both share images and stacked results to deter attackers’ cheating. The experimental results demonstrate the proposed scheme is feasible.     

对安全有效的(t,n)多秘密共享认证方案的改进

最近,谢琪等人(2005)基于双密钥思想提出了一种多秘密共享认证方案。在他们方案的秘密重构阶段,每个成员必须同时使用两个子密钥来证实自己没有欺骗。本文给出了一种攻击方法表明他们的方案并不能有效抵制成员的欺骗。同时给出了一种改进方案,不仅弥补了谢琪等人方案的安全缺陷,而且在秘密重构时采用并行算法来降低运算复杂度。