A hierarchical threshold secret image sharing

In the traditional secret image sharing schemes, the shadow images are generated by embedding the secret data into the cover image such that a sufficient number of shadow images can cooperate to reconstruct the secret image. In the process of reconstruction, each shadow image plays an equivalent role. However, a general threshold access structure could have other useful properties for the application. In this paper, we consider the problem of secret shadow images with a hierarchical threshold structure, employing Tassa’s hierarchical secret sharing to propose a hierarchical threshold secret image sharing scheme. In our scheme, the shadow images are partitioned into several levels, and the threshold access structure is determined by a sequence of threshold requirements. If and only if the shadow images involved satisfy the threshold requirements, the secret image can be reconstructed without distortion.     

基于区域卷积神经网络的图像秘密共享方案

数字图像在如今网络高速发展时代已成为重要的信息载体,而对图像信息的安全保护也成为安全领域的重要研究课题.图像秘密共享方案是一种基于门限的密码学方案,能够为多个用户提供一种保护图像秘密信息的方案.该方案将秘密图像加密成若干个影子图像,分配给不同的用户.当用户的个数达到门限值后,原始图像可以被重构,否则用户无法获得原始图像的任何信息.图像信息的分类和识别是图像秘密共享的前提和基础,卷积神经网络(convolutional neural network,CNN)在图像分类和识别中具有较高的准确性和较快的速度.将基于卷积神经网络的图像识别和分类与图像秘密共享结合起来,将深度学习工具应用于图像信息保护,可以提高基于传统人工图像识别的图像保护方案的效率.首先采用区域卷积神经网络(region CNN,RCNN)模型对图像进行识别,根据所包含的信息内容将图像分割成重要性级别不同的若干区域,然后在此基础上构造2种图像秘密共享方案,渐进式重构图像秘密共享方案以及具有重要影子图像的图像秘密共享方案.其中重要性级别较高的图像区域在图像重构中需要较高的门限,这一特性使得图像秘密共享方案能够适用于更多的应用场景.与传统的基于人工特征的图像识别方法相比,神经网络的引用能够提升图像分类和识别的效率,从而进一步提升了图像秘密共享的应用价值.     

基于恢复函数和误差扩散的灰度图像分存方案

基于((n,n)-阈值的灰度图像分存方案利用恢复函数和误差扩散技术将一张秘密灰度图像分存到n张有意义的灰度分存图像中。所提方案选择n张有意义的灰度图像作为分存图像,以增强秘密图像的隐蔽性,达到保护图像信息安全的目的;采用误差扩散技术,可以产生具有良好视觉质量的分存图像。所生成的分存图像没有像素膨胀,其大小与秘密图像相等。此外,方案的重构过程简单快速,而且是无损的。实验结果和理论分析表明,所提方案能为秘密图像分存提供一个高安全和有效的机制。     

A general (k, n) scalable secret image sharing scheme with the smooth scalability

A novel (k, n) scalable secret image sharing (SSIS) scheme was proposed to encrypt a secret image into n shadow images. One can gradually reconstruct a secret image by stacking k or more shadows, but he/she cannot conjecture any information from fewer than k shadows. The advantage of a (k, n)-SSIS scheme is that it provides the threshold property (i.e., k is a threshold value necessary to start in to reveal the secret) as well as the scalability (i.e., the information amount of a reconstructed secret is proportional to the number of shadows used in decryption). All previous (k, n)-SSIS schemes did not have the smooth scalability so that the information amount can be “smoothly” proportional to the number of shadows. In this paper, we consider the smooth scalability in (k, n)-SSIS scheme.     

A novel secret image sharing scheme in color images using small shadow images

Over the past several years, secret image sharing techniques have become another branch of the effort to prevent secret images from being eavesdropped on, in addition to traditional cryptography. Because smaller shadows can speed up the transmission of a secret color image, in this paper we combine Chang and Wu’s gradual search algorithm for a single bitmap BTC (GSBTC) and Shamir’s (k, n) threshold concept to propose a novel secret color image sharing scheme that generates smaller shadows. Experimental results confirm that the proposed scheme successfully reduces shadow size and that each shadow behaves as a random-like image that prevents leakage of information about the secret color image. Furthermore, the correlation between two vertically or horizontally adjacent pixels in each shadow is significantly less than those in a color secret image, and the presented scheme also achieves, on average, an NPCR = 0.414% and AUCI = 32.78%. Thus, with our scheme one-pixel difference could cause a significant difference in the corresponding shadows. Therefore, the security of the presented scheme is also confirmed.     

Progressive sharing for a secret image

Based on the wavelet transform, a new progressive sharing scheme is proposed to share a secret image into several shadow images using SPIHT encoding processes and Shamir’s threshold scheme. Quality refinement of the recovered image is achieved by the data consumed from the threshold number (r) of shadow images and each single shadow image reveals no information about the secret image. The size of each shadow image is smaller than 1/r of the secret image and any number of shadow images that is less than r reveals no information about the secret image. The proposed approach is secure for image sharing and provides excellent peak signal-to-noise ratio (PSNR) versus rate performance. Experimental results have demonstrated the promising performance of this method in progressive sharing.     

Image secret sharing method with two-decoding-options: Lossless recovery and previewing capability

Visual cryptography scheme (VCS) is a research area in image secret sharing, where one can easily stack shadow images and decode a black-and-white secret image through the human visual system without computation. Although VCS does not provide a competitive reconstruction quality, its stacking-to-see property clearly has the intended applications. To develop the ease of decoding of VCS and simultaneously overcome its weakness, Lin et al. recently proposed a novel two-in-one image secret sharing scheme (TiOISSS) with two decoding options based on VCS and a polynomial-based image secret sharing scheme (PISSS). In this TiOISSS, the first decoding stage has the stacking-to-see property to preview a vague image, and the second decoding stage is to obtain the original gray-level secret image. In this paper, we design a new TiOISSS by combining VCS and PISSS in a different way; in specific, our new scheme reduce shadow image size, and is more suitable for faster transmission within a distributed multimedia system.     

A lightweight authenticable visual secret sharing scheme based on turtle shell structure matrix

This paper proposes a novel visual secret sharing scheme based on a turtle shell structure matrix (TSSM) with reversibility and lightweight authentication. With the assistance of TSSM, the secret data is embedded into the original cover image and three meaningful shadow images are generated. To increase the image quality of the generated shadows, the proposed scheme designs an embedding structure that will be used to embed a secret image into shadows based on the TSSM, rather than by directly embedding authentication codes. The designed embedding structure offers a robust authentication capability at the cost of lightweight computation. Moreover, the hidden secret data can be extracted completely and the cover image can be restored losslessly through the collaboration of the three received shadows. Experimental results, on various grayscale test images, confirmed that our proposed scheme provides high visual quality and excellent authentication.

     

A novel mapping-based lossless recovery algorithm for VSS

The disadvantages of the existing lossless recovery algorithms in visual secret sharing (VSS) are that n shadow images or complex computation operation (i.e., Lagrange interpolations) is required in the recovering phase. Inspired by this, a novel mapping-based lossless recovery algorithm (MbLRA) for VSS is proposed in this paper. MbLRA at least has two merits: (1) compared with the previous schemes, less number of shadow images (may be n or less than n) are required in the proceeding of lossless recovery. (2) Secret image can be reconstructed losslessly by using simple addition operation. The MbLRA proves that the condition of lossless recovery is \(\xi 0_n \cap \xi 1_n =\emptyset \) and \(t_r\) is the least number of the shadow images which can recover the secret losslessly by analyzing the Hamming weight of adding all n shadows. Experiments are conducted to evaluate the efficiency of the proposed scheme.     

Preserving user-friendly shadow and high-contrast quality for multiple visual secret sharing technique

Traditional secret sharing scheme that encrypts secret image based on mathematical calculation to construct shadows often requires the complicated computation to extract the secret. Later on, conventional visual cryptography scheme was developed to deal with the perplexed calculation in encryption and extraction of previous schemes. The stack-to-see technique can be used easily to reveal the secret by human visual system, which can shorten computation time. However, the expansion of image size and the noise-liked shares of previous schemes lead to the difficulty in transmission and storage. This study uses a pre-defined codebook to encode two secret images into two meaningful transparencies without pixel expansion. According to the turning mechanism, two secret images can be embedded into two shares simultaneously. The decryption process allows the user to get two secrets via turning and stacking. A notable feature of our scheme is that the black pixel value of the secret image can be completely extracted and the vision quality of stacking results can be identified clearly.     

Sharing and hiding secret images with size constraint

This paper presents a method for sharing and hiding secret images. The method is modified from the (t,n) threshold scheme. (Comput.Graph. 26(5)(2002)765) The given secret image is shared and n shadow images are thus generated. Each shadow image is hidden in an ordinary image so as not to attract an attacker's attention. Any t of the n hidden shadows can be used to recover the secret image. The size of each stego image (in which a shadow image is hidden) is about 1/t of that of the secret image, avoiding the need for much storage space and transmission time (in the sense that the total size of t stego images is about the size of the secret image). Experimental results indicate that the qualities of both the recovered secret image and the stego images that contain the hidden shadows are acceptable. The photographers who work in enemy areas can use this system to transmit photographs.     

A novel (n,t, n) secret image sharing scheme without a trusted third party

Secret image sharing is a technique to share a secret image among a set of n participants. A trusted third party embeds the secret image into the cover image to generate shadow images such that at least t or more shadow images can reconstruct the secret image. In this paper, we consider an extreme and real-world situation, in which there is no one who is trusted by anyone else. In the proposed scheme, the participants can act as a dealer and communicate with each other in a secret channel. Each participant can generate her/his own shadow image independently, according to the cover image and the secret image. Experimental results are provided to show that the shadow images have satisfactory quality. In addition, our scheme has a large embedding capacity, and the secret image can be reconstructed losslessly.     

基于ElGamal密码体制的可验证秘密共享方案

基于ElGamal密码体制,提出了一个新的可验证秘密共享方案.方案中,秘密份额由各个参与者自己选择,秘密分发者不知道各个参与者所持有的份额,而且秘密份额长度与共享秘密长度相同.重构秘密时,任一参与者只需计算一次即可确认参与者中是否存在欺诈者,欺诈成功的概率可忽略不计.若存在欺诈者,则可通过秘密分发者来确定欺诈者身份.该方案具有充分的秘密信息利用率和较少的验证计算量.当共享秘密更换时,参与者不必更换自己的秘密份额.并且,每个参与者只需维护一个秘密份额,就可以实现对多个秘密的共享.方案的安全性是基于ElGamal密码体制和Shamir门限方案的安全性.     

对基于单向函数的He-Dawson多步骤秘密共享方案的改进

在(t,n)门限秘密共享方案中,有n个参与者,至少t个参与者拿出自己的子秘密就能够同时重构m个秘密.He-Dawson提出了一个基于单向函数的多步骤秘密共享方案.但是他们的方案是一次方案而且不能抵抗合谋攻击.每个参与者的子秘密由参与者自己选取,所以不存在秘密分发者的欺骗.并且每个参与者能够验证其他合作者的欺骗.每个参与者选取的子秘密可以复用.并且组秘密可以以任意顺序重构.此方案还能够抵抗合谋攻击.本方案的安全是基于Shamir门限方案和RSA密钥体制.     

一个动态门限多重秘密共享方案

提出一个动态多重秘密共享方案,参与者的秘密份额由参与者自己选定,每个参与者只需维护一个秘密份额就可以实现对任意多个秘密的共享,并且一次可以共享多个秘密。在秘密恢复过程中,每个参与者都可以验证其他合作者是否存在欺诈行为;在参与者间不需要安全信道;当秘密更新、参与者加入或退出系统时,各参与者的份额无需更新。分析表明,该方案是一个安全、实用的秘密共享方案。     

动态门限多重秘密共享方案

提出一个动态的门限秘密共享方案。参与者的秘密份额由各参与者自己选择,秘密分发者无须向各参与者传送任何秘密信息,因此,他们之间不需要安全信道。当秘密更新、参与者加入或退出系统时,各参与者的份额无须更新。秘密份额的长度小于或等于秘密的长度。每个参与者只须维护一个秘密份额,就可以实现对多个秘密的共享。在秘密恢复过程中,每个参与者能够验证其他参与者是否进行了欺骗。该方案以Shamir的门限方案和RSA密码体制的安全性为基础,是一个安全、高效的方案。     

视图的秘密分享及其代数编码方法

视图的秘密分享是图像信息安全领域独具吸引力的研究问题。寻求秘密视图完全的(Perfect)和理想的(Ideal)门限秘密分享方案(也称图像门限分享的完备方案),则是其中富有挑战性的未决课题。文中引入灰度值域GF(2m)上像素矩阵秘密分享的新观点和相应的代数几何编码方法,实现了数字图像(t,n)门限秘密分享的一种完备方案。该方案能够将一幅或多幅秘密图像编码为n幅各具随机视觉内容,同时又共具(t,n)门限结构的影子图像(或称份额图像)。证明了这种秘密分享方案的(t,n)门限结构不仅是完全的而且也是理想的,并给出了提高像素灰度值域GF(2m)上图像秘密分享算法效率的“m位像素值的分拆与并行”方法。分析表明,该图像秘密分享方法可以应用于高安全等级的秘密图像的网络多路径传输、保密图像信息的分散式存储控制、高维图形码(Bar-code in k dimension)和弹出码(Popcode)等新一代信息载体技术的识读控制等各方面。     

动态广义秘密共享方案

基于RSA密码体制和Pinch方案[12]提出了一种动态广义秘密共享方案。方案可以防止分发者和参与者的欺诈;一个参与者秘密份额的泄漏不会影响其他成员秘密份额的安全性;当更新秘密后,参与者各自的秘密份额可以重用;方案不需要安全信道,降低了系统代价。     

基于Shamir门限秘密分享的图像可视加密算法

采用Shamir门限秘密分享方案,提出一种带有认证功能的图像可视加密算法。该算法主要思想是,先将二值秘密图像分块得到数据,然后使用Shamir的门限秘密共享方案得到子秘密数据,同时用SM2签名算法对秘密图像进行签名,并将分享数据和签名信息嵌入载体图像。还原时需要指定张数的子秘密图像进行信息的提取、还原与认证。仿真实验结果表明,该秘密图像分享方案提高了秘密图像存储与传输的安全性。     

Sharing secrets in stego images with authentication

Recently, Lin and Tsai and Yang et al. proposed secret image sharing schemes with steganography and authentication, which divide a secret image into the shadows and embed the produced shadows in the cover images to form the stego images so as to be transmitted to authorized recipients securely. In addition, these schemes also involve their authentication mechanisms to verify the integrity of the stego images such that the secret image can be restored correctly. Unfortunately, these schemes still have two shortcomings. One is that the weak authentication cannot well protect the integrity of the stego images, so the secret image cannot be recovered completely. The other shortcoming is that the visual quality of the stego images is not good enough. To overcome such drawbacks, in this paper, we propose a novel secret image sharing scheme combining steganography and authentication based on Chinese remainder theorem (CRT). The proposed scheme not only improves the authentication ability but also enhances the visual quality of the stego images. The experimental results show that the proposed scheme is superior to the previously existing methods.