Earticle

This paper proposes a zero-watermark scheme for identification photos based on QR code and visual cryptography. The method makes no changes to original images while embedding the QR code watermark. In order to ensure the security, we use Arnold transformation to scrambling the watermark. In the scheme, we use discrete wavelet transform and matrix norm computing to generate the invariant feature values against print-scan attacks. Then the VC scheme is applied to generate the secret image from the feature values and the disturbed watermark by using a codebook. In the extraction scheme, we get the secret image which is registered to certification authority and the feature values extracted from the examined image with VC scheme, and then apply inverse Arnold transformation to restore the watermark, finally repair position patterns of the QR code. The experimental results show that the proposed algorithm is effective and robust against attacks such as JPEG compression, add noise, multiple filters, scale, little angle rotation and crop, especial print-scan attacks.

In this paper, we propose a blind watermarking scheme based on dual transform domains of discrete wavelet transform and discrete fractional random transform. In order to achieve the robustness and security, we also use the visual secret sharing scheme to split the secret image into two shares and use hologram quantization to spread the watermark information and analyze the cover image detail. For the purpose of widely practical application, we use a QR code for the watermark information. The QR code is decomposed into two shares, the first share is generated by the random seed, and the second share is generated with the help of secret image and the first share. Firstly, the two shares are respectively transformed into a hologram by using the hologram quantization, and then a discrete fractional random transform is applied to them. The cover image is decomposed by two-dimension discrete wavelet transform. The subband generated watermark then is embedded into the intermediate frequency components of the cover image. The watermark extraction process is the reverse of the embedding process. Because of the spectrum characteristic and tear resistant of the hologram, the algorithm has good invisibility. The experimental results show that the proposed algorithm is effective and robust against JPEG loss compression, cropping, rotation and noise.

The rapid evaluation of image manipulation and tampering has evoked the need for protecting digital data. Therefore a copyright protection method is used to protect the user information known as watermarking. Watermarking is the major image processing technique used to authenticate digital data. In this paper a hybrid approach is proposed to protect the digital data and also authenticates the user information. The proposed approach is an improvement over traditional video watermarking approaches. It uses fractions from the watermarked image to embed into the unique frames of the original video. The whole approach is divided into three steps which are described in the next sections of this paper. To check the resilience and robustness of this approach, various attacks are implemented over the watermarked video. After attacks, watermark image is extracted from the watermarked video to check the robustness of this approach. The quality of the recovered watermarked image is analysed using bit error rate. Experimental results show that this approach is very robust compared to other approaches.

This paper proposes a zero-video watermark scheme based on 2D-DWT and pseudo 3D-DCT, otherwise Singular Value Decomposition and log-polar transform are applied. The method makes no changes to original images while embedding the owner information of images so as to achieve high transparency. The log-polar transform ensures that the method is robust to rotation operations. In order to achieve the high robustness and security, we use chaotic logistic mapping and spread spectrum (CLMSS) to spread the watermark information. we also use the visual cryptography (VC) scheme to split the secret image into two shares. In the scheme, we use spread spectrum to encode the watermark to a Code Division Multiple Access watermark and use dual transform and log-polar to generate the feature values. Then the visual cryptography scheme is applied to generate the secret image from the feature values and the watermark. In the extraction scheme, we use the secret image which is registered to certification authority and the feature values extracted from the examined image with visual cryptography scheme to generate the CDMA watermark, and then decrypt it to get the watermark information. The experimental are conducted to verify the robustness through a series of experiments.

Through to analyze the characteristics of the digital cartoon image, proposed a based on discrete cosine transform (DCT) and singular value decomposition (SVD) combined contourlet transform with zero watermarking algorithm, the algorithm first for image contourlet transform and then make the low-frequency subband DCT and SVD decomposition again after operation block, the largest singular value as the image feature extracting for zero watermarking structure. In order to improve the security of the algorithm, introducing into visual cryptography processing the watermark image, the zero watermarking features obtained and secret sharing for the logic operation is zero watermarking characteristics of the final value.. The simulation results show that the algorithm has strong robustness.

With the increasing threats on multimedia information sharing, degradation of security is one of the most important concerns. Visual Cryptography is an emerging field for improving the security level by encoding the secret video using encryption scheme and performs computational free decoding process. The secret sharing through visual cryptographic techniques for multiple stack users is not sufficient in providing high percentage result on video sharing domain. Video sharing did not develop source key properties for individual frames and as a result the quality estimation strategy on video frame was not achieved. Moreover, the target rate constraint for video quality under the encryption-decryption was not achieved. This encryption-decryption target key rate declines on arranging multiple sequences of frames from multiple stack users. To improve the quality of visual secret video sharing scheme, a Discrete Cosine Transform Chaos Cryptographic (DCTCC) mechanism is proposed in this paper. The main objective of DCTCC is to enhance the security level of different level video frame using the encryption key properties. Initially, sender takes the video of differing frame length and compresses the video on image using the Discrete Cosine Transformer. The Discrete Cosine Transformer based visual secret sharing of video in the image takes the luminance values and provides high lossless compression. Second, the embedded video frame is encrypted to perform the secret sharing (i.e., visual cryptographic) using the chaos method. The Chaos method uses the enhanced RSA key properties to improve the video quality estimation strategy. Chaos method in DCTCC works effectively with non-linear dynamic set of video frames from users and also with the discrete time dynamical video cryptographic system. On the decryption side, the chaos method is applied in the reverse procedural order to fetch the video quality of video frames from original image. Experiment is conducted on factors such as mean square error rate, and secret video sharing efficacy level and encryption time.

Visual cryptography scheme is a cryptographic technique which allows visual information (e.g. printed text, handwritten notes, and picture) to be encrypted in such a way that the decryption can be performed by the human visual system, without the aid of computers. There are various measures on which performance of visual cryptography scheme depends, such as pixel expansion, contrast, security, accuracy, computational complexity, share generated is meaningful or meaningless, type of secret images( either binary or color) and number of secret images(either single or multiple) encrypted by the scheme. Intent of this paper is on study and performance analysis of the visual cryptography schemes on the basis of pixel expansion, number of secret images, image format and type of shares generated.

Conventional visual secret sharing schemes generate noise-like random pixels on shares to hide secret images. It suffers a management problem, because of which dealers cannot visually identify each share. This problem is solved by the Extended Visual Cryptography Scheme (EVCS), which adds a meaningful cover image in each share. However, the previous approaches involving the EVCS for color images suffer from a pixel expansion problem. In this paper, we propose a general approach to solve the abovementioned problem; the approach can be used for color images in non computer-aided decryption environments. The proposed approach uses Feed Forward Network to construct the shares. The experimental results indicate that a solution to the pixel expansion problem of the EVCS is achieved. Moreover, the display quality of the recovered image is better than that obtained using other VC schemes.

This paper presents a new method for a visual cryptography scheme that uses phase masks and an interferometer. To encrypt a binary image, we divided it into an arbitrary number of slides and encrypted them using an XOR process with a random key or keys. The phase mask for each encrypted image was fabricated nuder the proposed phase-assignment rule. For decryption, phase masks were placed on any path of the Mach-Zehnder interferometer. Through optical experiments, we confirmed that a secret binary image that was sliced could be recovered by the proposed method.

In this paper, a novel robust medical images watermarking scheme is proposed. In traditional methods, the added watermark may alter the host medical image in an irreversible manner and may mask subtle details. Consequently, we propose a method for medical image copyright protection that may remedy this problem by embedding the watermark without modifying the original host image. The proposed method is based on the visual cryptography concept and the dominant blocks of wavelet coefficients. The logic in using the blocks dominants map is that local features, such as contours or edges, are unique to each image. The experimental results show that the proposed method can withstand several image processing attacks such as cropping, filtering, compression, etc.

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 t ($2{\leq}t{\leq} n$) 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 k = 2, Construction 1 is reduced to Hou and others' (2, n)-BPVCS.

In this paper, we proposed a new visual cryptography scheme based on optical interference which improves the contrast and SNR of reconstructed images comparing with conventional visual cryptography method. We divided an binary image to be encrypted into n slides. To encrypt them, (n-1) random independent keys and one another random key by XOR process between four random keys were prepared. XOR between each divided image and each random key makes encrypted n encrypted images. From these images, encrypted binary phase masks can be made. For decryption all of phase masks should be placed together in the interferometer such as Mach-Zehnder interferometer.

M.Naor와 A.Shamir의 시각암호는 기존의 비밀 분산법에서 분산/복호시 연산량이 많은 것과는 달리 인간의 시각에 의해서 직접 복호될 수 있는 방식이다. 본 논문에서는 시각암호의 화장 방식인 복수 화상을 숨기는 방식에서 숨기려는 비밀화상의 수가 증가함에 따라 share 크기가 기하 급수적으로 커지는 문제점을 해결하기 위하여 고정 가중치부호의 해밍 거리를 조정하여 share 크기를 줄이는 방법을 제안한다.

Optical visual cryptography was proposed by conjunction of the optical theory with the cryptography. However, it had some difficulties. The problems occurred in the process of transferring data processing system from visual to optics. Therefore, it is appropriate to approach these problems in terms of optics. The results show that the optical visual cryptography system has both the effectiveness and reliability as well as real-time implementation property.

본 논문에서는 인간의 시각에 의해 비밀 정보를 간단히 복호할 수 있는 시각암호를 이용하여 하드 카피화상에 기밀정보를 분산시키는 기법에 대하여 고찰한다. 농도 패턴법에 의해 구성된 슬라이드를 시각암호의 관점에서 보면 해밍 가중치가 다르기 때문에 각 슬라이드는 원 화상의 형태를 유지하게 된다. 따라서, 슬라이드의 중첩에 의하여 분산된 기밀정보를 복원할 수 있을 뿐만 아니라 원 화상의 정보를 유지할 수 있는 이점을 갖게 된다. 본 논문에서는 하드 카피 화상에 기밀정보를 합성하기 위해 고안된 ONM(Oka-Nakamura-Matsui)방식을 확장하여 복수의 원 화상에 기밀정보를 분산시키는 방식을 제안한다. 그 결과, 저작자의 검증용 화상과 배포된 복수의 화상의 중첩만으로 저작권을 식별할 수 있는 디지털 워터마크에 응용할 수 있음을 보인다.

In this paper, we consider the method which a secret information is distributed in hard-copied image using visual cryptography that the secret can be identifying simply by human eyes. If slides constructed by patterning, which is one of dithering method, are considered from the viewpoint of visual cryptography, each slides will maintain the shape of original image because these slides have different Hamming weights. Therefore, this method has the advantage that information distributed into slides by stacking them can decode and the shape about the original image can be keeping as well. In this paper, we propose the method which shares the secret information into multiple original images by extension of ONM (Oka-Nakamura-Matsui) method which is devised to embed a secret information on hard-copied image. As a result, this proposed method is applicable to digital watermark because the copyright of image can be identified by stacking an image of owner for verification and the distributed multiple images.

We propose the encrytion method using visual cryptography and virtual phase images. The decryption is able to be performed when anyone got all of the keys. Original information is extracted by using Mach-Zehnder interferometer.

In this paper, we proposed an optical encryption method based in the concept of visual cryptography and interferometry. In our method a secret binary image was divided into two sub-images and they were encrypted by 'XOR' operation with a random key mask. Finally each encrypted image was changed into phase mask. By interference of these two phase masks the original image was obtained. Compared with general visual encryption method, this optical method had good signal-to-noise ratio due to no need to generate sub-pixels like visual encryption.

본 논문에서는 광 시각 암호기술에 근거한 개인 정보보호 방식을 제안하였다. 실험에 사용된 지문 데이터는 광 시각 암호 기술과 개방형 네트워크를 통해 전달된 공유 데이터의 일부를 고려한 secret sharing 방법에 의해 처리되었다. 필요에 따라 한 개인은 자신의 지문을 다른 공유 정보에 제공하는 방식으로 본인의 것을 확인할 수 있다. 다양한 환경 조건에서도 어려움 없이 효과적으로 지문을 인식 할 수 있음을 실험을 통해 검증하였다.

We propose an individual authentication method based on optical visual cryptography in thata fingerprint data is processed by secret sharing method taking into account the optical visual cryptograph and a part of shared data transmitted through an open network. Whenever it is necessary, submitting his fingerprint with the other shared information can authenticate the owner of the fingerprint. The system efficiently identifies fingerprints through optical correlation, regardless of difficulties of acquisition of exact fingerprint imagein the various environments.

지문 데이터를 광시각암호에 적합하게 Secret Sharing하고 Share 데이터의 일부를 공개된 네트워크로 전송하고 지문의 소유자가 나머지 Share를 소유하고 있다가 필요 시 지문과 함게 Share를 제시하여 본인임을 인식시키는 광시각암호 기반의 생체정보보호 방범을 제안한다.

We propose a biometrical information security method based on Optical Visual Cryptography in that a fingerprint data is processed by Secret Sharing method taking into account the Optical Visual Cryptography and a part of shared data transmitted through an open network. Whenever necessary the owner or the fingerprint can be authenticated by submitting his fingerprint with the other shared information.

시각암호는 복잡한 암호학적 연산 없이 인간의 시각에 의해 비밀정보를 직접 복원할 수 있는 간단한 방식이다. 이 방식은 영상 형태의 비밀정보를 n개의 랜덤한 영상(슬라이드)으로 분산시킬 때, 각 화소가 화장되면서 복원영상의 크기가 커지고 휘도가 떨어지는 결정이 있다. 따라서, 확장 화소의 수를 줄이고 휘도를 개선하는 연구가 많이 이루어져 오고 있다. 본 논문에서는 기저행렬의 행을 중첩시켜 (k, n)시각암호의 휘도를 개선하기 위한 새로운 구성법을 제안하고, 그룹 내 n개의 슬라이드 중 k개 이상의 슬라이드를 선택하는 방법에 따라 복수의 휘도를 갖는 (k, n) 시각암호를 구성할 수 있음을 보인다.

visual cryptography is a simple method in which secret information can be directly decoded in human visual system without any cryptographic computations. This scheme is a kind of secret sharing scheme in which secret of image type is distributed to n random image(we call it share). When the secret image is distributed to n shares, the original pixel is expanded as much as the size of column in basis matrix. It causes the deterioration of contrast in docoded secret image. Therefore, many researches have performed to reduce the size of pixel expansion and to improve the contrast by overlapping the row in basis matrix for (k, n) visual cryptography. In addition, we show that the proposed method can construct the (k, n) visual cryptography with multiple contrasts depending on selecting k out of n slides in a group.