Application of dynamic visual cryptography for optical control of chaotic oscillations

This paper proposes an optical experimental technique for the optical control of chaotic oscillations. Technique is based on the application of dynamic visual cryptography for chaotic oscillations. Initially, the secret information is encoded into a single stochastic moiré grating, which is fixed onto the surface of the vibrating structure. It is shown, that the secret can be visually decoded if the cover image oscillates according to a chaotic law. Therefore, a simple visual inspection can be used to determine if the parameters of the chaotic oscillations remain in the allowed range

New Designs for Friendly Visual Cryptography Scheme

NSC101-2221-E-032-047[[abstract]]Different from conventional cryptography, visual cryptography is an image cryptographic technique proposed by Naor and Shamir. It encodes a secret image into n pieces of noise-like shares. When k or more than k pieces of shares are gathered from participants, human visual system will disclose the secret image on the stacked image easily. Neither complicated mathematical computation nor any knowledge of cryptography are needed are the main advantages of visual cryptography. In this paper, we propose a new design for friendly visual cryptography scheme. The secret will be hiding into two meaningful shares. The black-appearing ratio in each block of the shares for the corresponding black (rep. white) secret pixel is the same. Therefore, it is impossible for one to disclose any information related to the secret image on each share, which achieves the goal of improving security. When shares are superimposed, the contours of the cover image will disappear on the stacked image, which will only reveal the secret image. According to our experimental results, the contrasts of the shares or the stacked images are good which can reveal the contents of the cover images and the secret image clearly.[[notice]]補正完畢[[journaltype]]國外[[ispeerreviewed]]Y[[booktype]]紙本[[countrycodes]]SG

Visual Cryptology Based on Wavelet Transform

Transmissions such as bank transactions, e-mail sending and retrieval, virtual shopping, etc. has become more and more common by people, institutions and organizations in daily life. This has also increased the importance of information security. There are many ways to ensure information security. In this study, one of these methods, visual cryptography, is used. During the data transfer, the data to be transmitted is divided into encrypted shares depending on a certain algorithm based on wavelet transfom. Then, the allocated shares are buried into meaningful images. Doing so, both the security of the transmitted data is ensured and the attention to the data which is divided into the encrypted shares is prevented.Günlük hayatta kişi, kurum ve kuruluşlar tarafından kullanımı hızla artan bankacılık işlemleri, e-posta gönderimi ve alımı, sanal alışveriş gibi işlemler bilgi güvenliğinin önemini de giderek arttırmıştır. Bilgi güvenliğini sağlamak için bir çok yöntem vardır. Bu çalışmada, bu yöntemlerden biri olan görsel kriptografi kullanılmıştır. Bilgi aktarımı sırasında, gönderilecek olan veriler dalgacık dönüşümüne dayalı belirli bir algoritmaya bağlı olarak şifreli paylara ayırılmıştır. Daha sonra ayrılan paylar anlamlı görüntülere gömülerek, hem gönderilen verilerin güvenliği sağlanmaktadır, hem de şifrelenmiş paylara ayrılan verinin dikkat çekmesi önlenmektedir

On Real-valued Visual Cryptographic Basis Matrices

Visual cryptography (VC) encodes an image into noise-like shares, which can be stacked to reveal a reduced quality version of the original. The problem with encrypting colour images is that they must undergo heavy pre-processing to reduce them to binary, entailing significant quality loss. This paper proposes VC that works directly on intermediate grayscale values per colour channel and demonstrates real-valued basis matrices for this purpose. The resulting stacked shares produce a clearer reconstruction than in binary VC, and to the best of the authors’ knowledge, is the first method posing no restrictions on colour values while maintaining the ability to decrypt with human vision. Grayscale and colour images of differing entropies are encrypted using fuzzy OR and XOR, and their PSNR and structural similarities are compared with binary VC to demonstrate improved quality. It is compared with previous research and its advantages highlighted, notably in high quality reconstructions with minimal processing

A Visual Secret Sharing Technique for Secure and Fast Transmission of Image

ABSTRACT: In the advent of booming communication technology, the needs for information sharing and transfer have increased exponentially which requires more and more new techniques to meet the increasing needs of a modern society. 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. Random grid based technique is a non expanded visual cryptographic technique for generating both meaningless and noise like shares. In this paper the idea is to increase the levels of security and to enhance the transmission speed of secret information over the network, as the basic model of Visual Cryptography is not an efficient tool to hide the information. In the proposed scheme initially the image is encrypted by Visual Cryptography using Random Grids and we propose a technique using combined DCT based Compression with Steganography for the speed transmission and additional security of encrypted random image shares over the transmitting media. The experimental results demonstrate the feasibility of the proposed scheme. KEYWORDS: Visual cryptography; Compression; DCT; Random grid; Shares; Steganography I. INTRODUCTION In the recent communication technology, the needs for information exchange and transfer have increased exponentially. In the public domain the threat of an intruder accessing secret information has been an ever existing concern for the data communication. Steganography, Cryptography, and Visual cryptography are the most widely used techniques to overcome these threats. In Cryptography the plaintext is transformed (encrypting it) into an unreadable format, which is called as called cipher text. Only those who possess a secret key can decipher (or decrypt) the message into plain text. In steganography a message, image, or file is embedded within another message, image, or file. Both these techniques provide some level of security of data. In VC the image is encrypted by creating random shares and decryption is done by human eyes. However, neither of them alone is secure enough over an unsecure communication channel for sharing information and is vulnerable to intruder attacks. Although these techniques are often combined together to achieve higher levels of security, in order to minimize the threat of intrusion we still need a highly secured system to transfer information over any communication media. For any communication system, a secure transmission of information can be achieved using a powerful encoding algorithm and a fast transmission to send the information from a transmitter to a receiver (that can be done using an efficient compression technique) is two important requirements. To satisfy these constraints, we propose a new method of compression and encryption at same time. The image is initially encrypted by visual cryptography using random grid scheme by generating random shares. Then we cover the random share with a cover image. Our proposed method is based on the hiding of information (Embedding) in the transmitter side and taking out (Extracting) algorithm in receiver side the decoding phase. In addition we would like to compress the transmitting data, to achieve a high speed communication. For this purpose Discrete Cosine Transform (DCT) is utilized because most of the power is concentrated in the lower frequency bands by DCT, it is used to cut out the higher frequency components. Then the compressed DCT elements are rotated, the rotations have another aspect. The directions and degrees of the rotations are saved as "key" to restore the original images. If the receiver does not know "key," it is hard to recover the original images

On the Use of Secret Sharing as a Secure Multi-use Pad

Secret sharing (SS) is a cryptographic method proposed independently by Adi Shamir and George Blakley in 1979 to encode the keys of public-key cryptography by splitting them into maximally entropic shares that are distributed to participants, only revealing the secret when combined. Each new sharing instance, even of the same key, produces a different set of shares to distribute anew. This paper investigates SS as an independent cipher to secure confidential messages between a limited set of trusted participants by eliminating the need to redistribute shares. A participant's master share is permanently fixed and unlimited temporary shares are created and combined with it to reveal new messages. Security is argued against specific and general attacks

Efficient Random Grid Visual Cryptographic Schemes having Essential Members

In this paper we consider ``OR based monochrome random grid visual cryptographic schemes (RGVCS) for $t$-$(k,n)^*$ access structure which is a generalization of the threshold $(k,n)$ access structure in the sense that in all the successful attempts to recover the secret image, the $t$ essential participants must always be present. Up to the best of our knowledge, the current proposed work is the first in the literature of RGVCS which provides efficient direct constructions for the $t$-$(k,n)^*$-RGVCS for ``OR based model. Finding the closed form of light contrast is a challenging work. However, in this paper we come up with the closed form of the light contrast for the ``OR based model. In literature, there are visual cryptographic schemes where the secret reconstruction is done by binary ``XOR operation instead of ``OR operation to increase the relative contrast of the decoded image. In this paper, we also propose an extended grid based $t$-$(k,n)^*$-RGVCS in which we replace the traditional ``OR operation by ``XOR operation. Note that the use of XOR operation indicates that the decoding must be performed computationally and not visually. We justified our schemes using both experimental as well as simulation based data

植基於區塊漸進還原之非擴展式視覺機密分享

[[abstract]]In the related works of progressive visual secret sharing (PVSS), Wang et al. (2007) and Wang (2009) all have the following drawbacks: (1) The design of the dispatching matrices is not regular. (2) Shares are m-times larger than the original secret image. (3) Restored image's quality is poor. (4) Their schemes are not suitable to apply in grayscale and color secret images. In order to solve the above limitations, we propose a non-expanded PVSS approach, in which the recovery method is based on secret blocks, namely Block-based Progressive Visual Secret Sharing (BPVSS). We divide a secret image into n non-overlapped image blocks, and an additional portion of secret will be restored after superimposing one more transparency. When superimposing any t shares, there have t (2≤t≤n) secret blocks being restored. Compared with other related works, BPVSS has several advantages: (1) The concept of this model is concise, easy to implement, and the number of participants will not be restricted. (2) In the situation of noise-like shares, the contrast of the restored image is 50%, which means that the hidden message can be clearly recognized by the naked eyes. (3) When transparencies are shifted from noise-like into meaningful, the contrast of the stego-image and the restored image will be 25% which is still superior to other related studies. (4) Our scheme is more suitable for grayscale and color secret images than previous related studies. (5) The size of transparencies is the same as the size of secret image.[[notice]]補正完畢[[incitationindex]]TSSCI[[booktype]]電子