基于误差扩散算法的（2，2）可视密码方案

为解决传统可视密码存在像素膨胀及分存图像无意义等问题,研究并实现了将黑白反色的密图嵌入到两个灰度图像的方法。通过采用对灰度图像进行预处理增加分存图像叠加后,黑色像素恢复的概率以及在误差扩散的过程中同时嵌入密图信息、适当降低白色像素恢复概率以及恢复黑色像素时随机选择修改其中一个分存图像的方法,有效地提高了分存图像的质量。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。     

具有理想对比度的可视密码方案

提出了一种可视密码方案,该方案基于完美的黑度可视密码方案(PBVCS)和非完美的可视密码方案(NPBVCS),应用简单的布尔运算和移位运算,获得了理想的对比度.同时实现了重构的图像与原秘密图像保持一致,没有像素扩展,而且运算简单,易于实现.     

基于可视密码的身份认证技术方案

可视密码技术是密码学领域近年来发展起来的针对图像的加、解密技术,具有隐蔽性好、安全性高、秘密恢复的简单性等特点。而身份认证技术是为了确认用户在生活、工作、消费等活动中的真实身份而产生的有效解决办法,对保障用户身份的真实性和可靠性有着举足轻重的作用。本文引入可视密码技术,提出一种基于可视密码的身份识别技术方案,用户携带的信息通过加密手段保障不被他人非法窃取利用,提高了信息携带过程的安全性与隐私性。     

以可视密码为基础的身份识别技术方案分析

可视密码是近几年信息安全领域新兴的一种针对图像的加密和解密技术,其隐蔽性、安全性、私密恢复等性能优异。身份识别是信息安全领域中重要的组成部分,是保障系统安全性的重要关卡。该文以可视密码技术为基础,提出一种以可视密码为基础的身份识别技术方案,将可是密码技术和身份识别技术进行结合,从而得到一种基于可视密码的只能卡口令识别方案,对该方案进行了介绍分析,并通过仿真实验对方案可行性进行了验证进行。该文中提出的方案对于提高用户携带信息的安全性有重要意义。     

一种可防止多个欺骗者的可视密码方案

为了防止参与者在秘密恢复阶段提供假的子秘密,影响共享秘密的正确恢复,提出了一种多秘密共享可视密码构造方案,并给出了其在可防止多个欺骗者应用上的算法描述。通过多秘密共享可视密码（2,3,4,4）的构造,实现了两个欺骗者的检测。实验发现,本文提出的方案和相应的算法,在防止和发现多个欺骗者的应用上有很强的优越性。     

一种基于可视密码的轮廓小波图像零水印方案

为了实现数字图像的版权保护,提出了一种基于可视密码的零水印方案.该方案首先实现了一种轮廓小波变换(CWT)的多尺度几何分析方法,然后通过在变换域能量最高的中频子带适当选取系数,结合预定义的可视密码码书,将二值水印图像藏匿于两个分享中,从而构造出零水印信号.实验结果表明,该方案不仅能在不改变原始图像的情况下实现版权保护,而且鲁棒性强,能抵抗JPEG压缩、剪切、加噪、锐化及旋转等图像处理攻击.     

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.     

On the Contrast in Visual Cryptography Schemes

A visual cryptography scheme is a method to encode a secret image SI into shadow images called shares such that certain qualified subsets of shares enable the ``visual' recovery of the secret image. The ``visual' recovery consists of xeroxing the shares onto transparencies, and then stacking them. The shares of a qualified set will reveal the secret image without any cryptographic computation. In this paper we analyze the contrast of the reconstructed image in k out of n visual cryptography schemes. (In such a scheme any k shares will reveal the image, but no set of k-1 shares gives any information about the image.) In the case of 2 out of n threshold schemes we give a complete characterization of schemes having optimal contrast and minimum pixel expansion in terms of certain balanced incomplete block designs. In the case of k out of n threshold schemes with we obtain upper and lower bounds on the optimal contrast. Received 27 September 1996 and revised 13 February 1998     

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.     

Nested Visual Cryptography Scheme

A new nested visual cryptography scheme is proposed for n cooperated user groups. It can encode the secret image consists of black and white pixels into share images which should be distributed to each user in each group. To decode the secret, users in at least k out of n groups should be present, and at least p out of q users should provide their shares for each attendant group （where p and q can be distinct for each group）. For the proposed scheme, the known scheme can be regarded as a simple instance which has only one user in each group. Compared to S-extended visual cryptography scheme, there is no need to enumerate all the user sets which can decode the secret.     

Constructions and Properties of General (k,n) Block‐Based Progressive Visual Cryptography

Recently, Hou and others introduced a (2, n) block‐based progressive visual cryptographic scheme (BPVCS) in which image blocks can be gradually recovered step by step. In Hou and others’ (2, n)‐BPVCS, a secret image is subdivided into n non‐overlapping image blocks. When participants stack their shadow images, all the image blocks associated with these t participants will be recovered. However, Hou and others’ scheme is only a simple 2‐out‐of‐n case. In this paper, we discuss a general (k, n)‐BPVCS for any k and n. Our main contribution is to give two constructions (Construction 1 and Construction 2) of this general (k, n)‐BPVCS. Also, we theoretically prove that both constructions satisfy a threshold property and progressive recovery of the proposed (k, n)‐BPVCS. For , Construction 1 is reduced to Hou and others’ (2, n)‐BPVCS.]     

一种新的多秘密分享视觉密码

 本文给出了一种新的多秘密分享视觉密码的定义,能够支持多授权子集和共享份操作.基于区域标记和单秘密视觉密码的基础矩阵,设计了多秘密分享与恢复的流程,给出一种实现方案.最后对方案的有效性进行了理论证明和实验验证.     

Secret Sharing Using Visual Cryptography

Compared with the traditional cryptography,visual cryptography(VC) decrypts secret images referring to the characteristics of human vision,rather than the cryptography knowledge or complex computations.Furthermore,seeing to the freeness of the secret key,the whole process of encryption as well as decryption for the visual cryptography meets a fast dealing course.As to the security concern,it is able to guarantee that no one can have access to any clues about the content of a secret image from individual cover images.Thus,owing to the studies on this area,the target of light-weighted cryptography is reached.Now the visual cryptography has been developed from the meaningless shadows to the meaningful ones.Seeing to the highly developed technique,some advanced VC techniques are introduced in this survey,respectively.     

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。     

基于可视密码术的小波域音频数字水印研究

提出的基于可视密码术的小波域量化系数音频数字水印方案,采用可视密码术的方法,通过特定算法将秘密信息隐藏到一定数量的图片中,这些图片作为水印嵌入到数字作品中,恢复者可以通过将特定数量的图片叠加在一起,通过人的视觉系统就能识别恢复出原来的秘密信息,无需大量的计算和密码学的知识,所以可以为更多的人使用。