Visual secret sharing scheme for (<Emphasis Type="Italic">k</Emphasis>, <Emphasis Type="Italic">n</Emphasis>) threshold based on QR code with multiple decryptions

In this paper, a novel visual secret sharing (VSS) scheme based on QR code (VSSQR) with (k, n) threshold is investigated. Our VSSQR exploits the error correction mechanism in the QR code structure, to generate the bits corresponding to shares (shadow images) by VSS from a secret bit in the processing of encoding QR. Each output share is a valid QR code that can be scanned and decoded utilizing a QR code reader, which may reduce the likelihood of attracting the attention of potential attackers. Due to different application scenarios, two different recovered ways of the secret image are given. The proposed VSS scheme based on QR code can visually reveal secret image with the abilities of stacking and XOR decryptions as well as scan every shadow image, i.e., a QR code, by a QR code reader. The secret image could be revealed by human visual system without any computation based on stacking when no lightweight computation device. On the other hand, if the lightweight computation device is available, the secret image can be revealed with better visual quality based on XOR operation and could be lossless revealed when sufficient shares are collected. In addition, it can assist alignment for VSS recovery. The experiment results show the effectiveness of our scheme.     

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.

     

Random grid-based threshold visual secret sharing with improved visual quality and lossless recovery ability

Visual secret sharing (VSS) by random grids (RG) has gained much attention since it avoids the pixel expansion problem as well as requires no basic matrixes design. However, most of the previous RG-based threshold VSS still suffer from low visual quality or worse reconstructed secrets when more shadows are stacked. In this paper, a new RG-based threshold VSS with improved visual quality and lossless recovery ability is proposed. The random bits are utilized to improve the visual quality as well as to decrease the darkness of the reconstructed secret image. And the secret image can be losslessly recovered in the proposed scheme if the computational device is available. Simulation results and analyzes show the effectiveness of the proposed scheme. In addition, this paper gave the preliminary definition and evaluation of progressive secret sharing (PSS) based on mathematical differential and expectations.     

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 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.     

A novel lossless recovery algorithm for basic matrix-based VSS

Lossless recovery is very important for visual secret share (VSS). In this paper, a novel lossless recovery algorithm for the basic matrix-based VSS is proposed. The algorithm has the merit of reconstructing secret image losslessly by using simple addition operation. The algorithm proves that the condition of lossless recovery of the secret image is ξ0 ∩ ξ1 = ? by analyzing the Hamming weight of adding all columns of basic matrixes. Simulations are conducted to evaluate the efficiency of the proposed scheme.

     

A two-level QR code scheme based on polynomial secret sharing

Quick Response codes (QR codes) are common two-dimensional machine readable codes used extensively in all walks of life due to their high reading speeds, high data density, and strong error correction capabilities. However, public encoding using QR codes poses a threat to information security. In this paper, we introduce a Two-Level QR code that protects private data by using the recognition patterns of QR codes and by use of polynomial secret sharing algorithms. On a public level, QR codes are decodable by any standard QR reader. For secure use, QR codes simultaneously store private information, allowing transmission of secret information via an open channel. Experimental results and analysis demonstrate that this proposed approach is both feasible and reasonable. It reduces the probability of attracting the attention of potential attackers. The secret image format can accommodate either binary or grayscale. In addition, the data capacity of the secret payload of this approach is much higher than other methods.

     

Secret sharing schemes from binary linear codes

In principle, every linear code can be used to construct a secret sharing scheme. However, in general, determining the access structure of the scheme is very hard. On the other hand, finding error correcting codes that produce secret sharing schemes with efficient access structures is also difficult. In this paper, we study a set of minimal codewords for certain classes of binary linear codes, and then determine the access structure of secret sharing schemes based on these codes. Furthermore, we prove that the secret sharing schemes obtained are democratic in the sense that every participant is involved in the same number of minimal access sets.     

Secret sharing: using meaningful image shadows based on Gray code

Steganography, such as secret sharing, is an important technique to use for protecting transmitted confidential data from the attention of any adversaries. Gray code is a commonly encountered binary labeling that was proposed by Frank Gray of Bell Laboratories in 1940 to prevent errors when using pulse-code modulation to transmit signals. The main features of Gray code are its recursive construction method and the fact that any two adjacent codes change only one bit. According to our observations, the image pixel correction based on these features is suitable for application secret sharing without making significant changes to the pixel value. We designed a reversible secret sharing method using meaningful image shadows based on Gray code. Our design applies absolute moment block truncation coding (AMBTC) compression to reduce the transmission bit rate. The experimental results show that our scheme can achieve the adequate visual quality of shadow images with lower communication overhead, thus proving it practical for numerous applications.     

Improved schemes for visual secret sharing based on random grids

Random grid (RG) is an alternative approach to realize a visual secret sharing (VSS) scheme. RG-based VSS has merits such as no pixel expansion and no tailor-made matrix requirement. Recently, many investigations on RG-based VSS are made. However, they need further improvements. In this paper, we obtain some improvements on RG-based VSS. Actually, two improved schemes are proposed, namely RG-based VSS for general access structure (GAS) with improved contrast and extended RG-based VSS with improved access structure. The first scheme can achieve better contrast than previous schemes. The second scheme reduces the chance of suspicion on secret image encryption by generating meaningful shares instead of noise-like shares in the first scheme, and improves the access structure from (k, k) to GAS while maintaining the property that the contrast of the recovered image is traded with that of share images by setting a certain parameter from small to large. Finally, theoretical analyses and experimental results are provided to demonstrate the effectiveness and advantages of the proposed schemes.

     

On the design of a two-decoding-option image secret sharing scheme

In an image secret sharing scheme (ISSS), two main categories are discussed. One is the polynomial-style image secret sharing scheme (PISSS), and the other is the visual secret sharing (VSS). It is interesting to combine the main properties of these two schemes. When the encoded secret images are received, we can decode them by combining these two schemes’ properties, utilizing the VSS property to seek the secret immediately by human visual system (HVS) and the PISSS property to recover the secret perfectly with a decoding machine. This paper combines PISSS and random grids-based VSS to remove all the drawbacks existing in the previous works including 1) distortion by compressing a secret image, 2) non-perfect reconstructed image, 3) distortion of pixel expansion, and 4) size-reduced halftone image. The experimental results demonstrate the proposed scheme does work well.     

A new two-level QR code with visual cryptography scheme

The Quick Response (QR) code is designed for information storage recognizable by machine vision. With the popularity of QR code applications, the security of QR codes becomes hot issues concerned by many scholars. In this paper, a novel QR code with two-level information storage is designed to protect private messages. In the meantime, the public level can be directly decoded by any standard QR reader. In contrast to other studies, the computational complexity of the proposed scheme is reduced by combining with the theory of visual cryptography scheme (VCS). In addition, an important characteristic of the QR code, error correction capability, is preserved in this paper, guaranteeing the robustness to QR code damage. Experimental results and analysis show that the proposed scheme is both feasible and reasonably secure, further enriching the application fields and outperforming the previous schemes significantly.     

A new visual cryptography with multi-level encoding

Visual secret sharing (VSS) is a visual cryptography scheme which decodes secret messages into several enlarged shares, and distributes them to different participants. The participants can recover the secret messages by stacking their shares, and then secret message can be revealed by human visual sensitivity. Afterward some researchers start to research size invariant scheme, and apply to encode grayscale images such as scenic photos or pictures, not only binary messages. Owing to the gray values distribution of pictures are different, extreme distribution may cause blurred revealed image. In this paper, we proposed a size invariant VSS scheme which is suitable for different distribution of image's gray values. Experiment results show that the reconstructed images of our method, for brighter, darker, and normal images, have clearer and higher contrast, and without apparent artifact and unexpected contour.     

基于最大秩距离码的私钥加密方案

Jordan和Rao基于纠错码提出了一种私钥加密方案,通过安全性分析可知,基于大数选举方法,此方案中的秘密矩阵能有效地获得。Gabidulin于1985年提出了秩距离码及最大秩距离码的理论,由于秩范数和秩距离码的特点,利用秩距离码构造密码系统,可用比较小的参数获得比较大的工作因子。Gabidulin,Paramonov和Tretjakov基于最大秩距离码提出了一种新的McEliece公钥密码系统,该文基于最大秩距离码提出了与其稍有不同的一种私钥加密方案。讨论了它的可行性及安全性,并证明了它比基于最大秩距离码的上述公钥密码系统更安全。     

基于自适应哈夫曼编码的密文可逆信息隐藏算法

随着云存储和隐私保护的发展,密文域可逆信息隐藏作为一种可以在密文中嵌入秘密信息,保证嵌入后的信息可以无错误提取,并能无损恢复原始明文图像的技术,越来越受到人们的关注.本文提出了一种基于自适应哈夫曼编码的密文域可逆信息隐藏算法,对不同的图像采用不同的哈夫曼码字编码腾出空间来嵌入秘密信息.首先利用自然图像相邻像素间的相关性对原始明文图像进行像素值预测,从最高有效位到最低有效位,对原始像素值和预测像素值的相同比特位进行自适应的哈夫曼编码标记.然后,利用流密码对原始明文图像进行加密.最后在腾出的空间,通过位替换来自适应的嵌入秘密信息.由于哈夫曼编码和解码的可逆性,合法接收者可以对原始明文图像和秘密信息实现分离的无损恢复和提取.实验结果表明,与现有的几种方法相比,本文提出的方法具有更好的安全性和更高的嵌入率,在BOSSBase、BOWS-2和UCID三个数据集上的平均嵌入率比MPHC算法分别提高了0.09bpp、0.062 bpp和0.06bpp,在最佳情况下比MPHC算法能分别高出0.958 bpp、0.797 bpp和0.320 bpp,最差情况下的嵌入率比MPHC算法也分别高出了 0.01 bpp、0.039 bpp和0.061 bpp.     

A novel two-in-one image secret sharing scheme based on perfect black visual cryptography

Perfect black visual cryptography scheme (PBVCS) shares a binary secret image into n shadows. Stacking any \(k(k<n)\) shadows can reveal a vague secret image, and the black area of the secret image is recovered as perfect black. Two-in-one image secret sharing (TiOISS) scheme is a secret image sharing method with two decoding options. It can not only decode a vague secret image by stacking any k shadows, but also reveal the original grayscale secret image with k shadows by computation. Researchers proposed some TiOISS schemes, which are based on visual cryptography and polynomial-based image secret sharing (PISS). Since PISS reveals the secret image by Lagrange’s interpolation, these TiOISS schemes need complex computation. In this paper, we proposed a novel TiOISS scheme based on PBVCS using exclusive OR operation. Compared with literature TiOISS schemes, our scheme does not need complex computation in revealing process, and it can be used in real-time application. The grayscale secret image can be recovered quickly with a few Boolean operations.     

Fast Component-Based QR Code Detection in Arbitrarily Acquired Images

Quick Response (QR) codes are a type of 2D barcode that is becoming very popular, with several application possibilities. Since they can encode alphanumeric characters, a rich set of information can be made available through encoded URL addresses. In particular, QR codes could be used to aid visually impaired and blind people to access web based voice information systems and services, and autonomous robots to acquire context-relevant information. However, in order to be decoded, QR codes need to be properly framed, something that robots, visually impaired and blind people will not be able to do easily without guidance. Therefore, any application that aims assisting robots or visually impaired people must have the capability to detect QR codes and guide them to properly frame the code. A fast component-based two-stage approach for detecting QR codes in arbitrarily acquired images is proposed in this work. In the first stage, regular components present at three corners of the code are detected, and in the second stage geometrical restrictions among detected components are verified to confirm the presence of a code. Experimental results show a high detection rate, superior to 90 %, at a fast speed compatible with real-time applications.     

Artistic QR Code Embellishment

A QR code is a two‐dimensional barcode that encodes information. A standard QR code contains only regular black and white squares, and thus is unattractive. This paper proposes a novel framework for embellishing a standard QR code, to make it both attractive and recognizable by any human while maintaining its scanability. The proposed method is inspired by artistic methods. A QR code is typically embellished by stylizing the squares and embedding images into it. In the proposed framework, the regular squares are reshaped using a binary examplar, to make their local appearances resemble the example shape. Additionally, an error‐aware warping technique for deforming the embedded image is proposed; it minimizes the error in the QR code that is generated by the embedding of the image to optimize the readability of the code. The proposed algorithm yields lower data error than previous global transformation techniques because the warping can locally deform the embedded image to conform to the squares that surround it. The proposed framework was examined by using it to embellish an extensive set of QR codes and to test the readability with various commercial QR code readers.     

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.