1. INTRODUCTION
Data or information is very crucial to any organization or any individual person. The data can be confidential, personal, and sensitive. The exchange of data among two parties must be done in a secured method so as to avoid any tampering. Thus securing the information becomes all the more necessary. The communication media i.e internet through which we send data may not be secured every time, so there is a need of other methods of securing data. Thus Information hiding becomes more necessary. Information hiding includes cryptography and steganography techniques. Cryptography was created as a technique for securing the secrecy of communication and many different methods have been developed to encrypt and decrypt data in order to keep the message secret. Unfortunately it is sometimes not enough to keep the contents of a message secret, it may also be necessary to keep the existence of the message secret. The technique used to implement this, is called steganography.
In Visual cryptography (VC) is a cryptographic technique, used to encrypt visual information i.e text, image, etc. The secret data is divided into two or more pieces. These pieces of information are called shares. The process of creating shares is called encryption. The secret data is retrieved by combining all or subset of collection of shares. This process of stacking the shares on one another to retrieve back the secret data is called decryption as shown in Figure 1[21*].
Figure 1: Visual cryptography schema
Steganography is science and art of invisible communication. This is accomplished through hiding information in other information so the existence of the communicated information is hided. The word steganography is derived originally from the Greek. The word “stegos” means “cover” and the word “graphy” means “writing” [7*], together defining it as “covered writing”. In image steganography the important or secret information is hidden exclusively in images. The secret image is hidden in a cover image to create a stego image at the sender side using steganography technique and this stego image is transmitted over the communication link to the receiver. On receiving this stego image, the secret image is retrieved by applying the de-stenography technique as shown in Figure 2a and 2b [5*].
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Figure 2a: Steganography at sender side
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Figure 2b: Steganography at receiver side
Steganography and visual cryptography are the two promising ways to protect information from unwanted parties. However by using either of the single technology alone, high protection to the information cannot be achieved. Once the presence of hidden information is revealed, the purpose of steganography is partly defeated [8*]. The strength of steganography can thus be amplified by combining it with cryptography. In steganography techniques the secret data is hidden in the cover image to create a stego image and transmitted over the network to receiver, this stego image looks like an cover image. The modification done to cover image is not noticeable and on receiving this stego image, receiver has to extract the secret data from the stego image.
Few best steganography measures:
High capacity: Maximum size of information (payload) can be embedded into mage.
Perceptual Transparency: is the measure of perceptual quality of stego image compared to cover image, since it degrades after hiding data into cover image.
Robustness: Data should not be lost or damaged when stego image goes in some transformation.
Temper resistance: Altering the data after embedding in to cover image should be difficult.
Computational complexity: is the measure of expensive of embedding and extracting the secret data.
Peak Signal to Noise Ratio: it abbreviated as PSNR, is an expression or an engineering term for the ratio between the maximum possible value (power) of a signal and the power of corrupting noise that affects the quality of its representation.
2. PROBLEM STATEMENT
In the today’s e-connected world, information sharing and transfer has been extensively increased. Communication of data over the network has exposed difficulty due to the threat imposed by the intruders .With the rapid advancement network topology, information is transmitted over the internet conveniently. Various confidential data such as military maps, criminal details, biometric details, etc., are transmitted over the internet, while transferring secret data and secret messages, security issues are considered , if not hackers may utilize weak link over network to steal the information. To overcome this security problem of secret images and secret message, secure advanced system by which we can safeguard our data while transferring on internet has to be proposed.
3. LITERATURE SURVEY
Securing Confidential data plays a major role in many sensitive applications, in order to provide it Visual Cryptography and Steganography approaches are used. There are techniques based on these approaches, but few techniques are weak in its own way. So during secure transmission of data, hackers try to break the security provided by steganography and cryptography techniques and retrieve the information. Few techniques are explained below.
High payload steganography mechanism using hybrid edge detector, Wen-Jan, Chin-Chen, T. Hoang, 2010. [13]
High capacity of hidden data is achieved by utilizing the LSB and hybrid edge detection scheme. For edge computation two types of canny and fuzzy edges detection methods are applied and the LSB substitution method is used to embed hidden data. Using this scheme data with higher peak signal to noise ratio (PSNR) is embedded with normal LSB method. using limited images dataset the is tested. The method is not tested using extensive edges based image like ‘Baboob.tif’
New adaptive least-significant bit (LSB) steganographic method using pixel-value differencing (PVD), Cheng-Hsing, Chi-Yao, Shiuh-Jeng, Hung-Min, 2008. [12]
Pixel value difference (PVD) and simple least significant bits schemes are used in adaptive least significant bits data embedding. The size of the hidden data bits in pixel value differencing (PVD) method is estimated by finding difference between the two consecutive pixels in cover image. PVD method provides a good imperceptibility by its unique way of determining the depth of the embedded bits by consecutive pixel difference. The large and adaptive k-LSB substitution is used at edge area of image and PVD is used at smooth region of image. By this way the technique provide both high visual quality and larger capacity.
Adaptive significant bit method, Swapnil S, Niranjan, 2014. [10]
An adaptive significant bit spatial domain embedding method is proposed. The secret data hiding is achieved by embedding data in least-significant-bit (LSB) of an image. The image pixels ranges are divided from 0-255 and private stego-key is generated, that has 5 different gray level ranges of image and each range indicates the fixed number of bits to be embedded in LSB of an image. The strength of this method is its integrity and high capacity of hiding secret information in stego-image.
RGB Intensity Based Variable-Bits Image Steganography, Mohammad Tanvir Parvez and Adnan Abdul-Aziz, 2008. [15]
In this pixel indicator technique with variable bits, A channel among red, green and blue channels is chosen and embeds data into variable LSB of chosen channel. Intensity of the pixel is used to decide the variable bits to embed into cover image. The channel selection is sequential and capacity depends on the cover image. This method has almost same histogram of cover and stego-image.
Steganography by using mapping of letters to pixels and indicator channels, Jatinder Kumar M, Ashish Oberoi,2010. [14]
In this image steganography approach the pixels of an image are mapped to alphabetic letters. where it maps 32 letters (26 for English alphabetic and other for special characters) with the pixel values. Five (5) bits used to represent these 32letters and a table is generated with 4 cases is designed to represent these 32 letters. According to that table, each letter can be represented in all 4 cases, which increases the probability of matching. It utilizes the image 7 MSB (Most Significant Bits) (27 = 128) bits for mapping and the algorithm keeps the matching pattern of cover-image which is then used for extracting data from the stego-image. Doesn’t needs any edge or smoothness computations but secret data should be in the form of text or letter for embedding .
A (2,2) Secret Sharing Scheme for Visual Cryptography without Pixel Expansion, Mahmoud E. Hodeish, Dr. V. T. Humbe, 2015[20]
In two-out-of two scheme for a binary image pixel of original image, two sub pixels either of black or white is randomly selected and random column permutation of white and black pixel is performed. This retains size of the pixel but not the color of the image.
High-Capacity Image Data Hiding Scheme Using Adaptive LSB Substitution, Hengfu YANG , Xingming SUN , Guang SUN, China, 2009. [11]
High capacity image data hiding is achieved by adpative LSB substitution. For better visual quality of stego-image noise sensitive area is taken care while embedding. Normal texture and edges area are taken as an advantage for embedding. In order to calculate the number of k-bit LSB for secret data embedding brightness, edges and texture masking of the cover image are subjected to analysis. At non-sensitive image region the value of k is high and k value remain small over sensitive to balance the overall visual quality of a stego image. For better stego-image visual quality of adaptive LSB substitution method utilizes the pixel adjustment method.
4. OBJECTIVES
1. To propose a New Visual Cryptography System for color images which also retains the color information, pixel size of the secret image retrieved and creates clueless color shares.
2. To propose a Novel Image Steganography technique for hiding Secret data(message and image),which is transmitted over the network
3. The proposed New Visual Cryptography system and Novel Image Steganography systems are combined to obtain highly secured, robust and efficient system to transfer the secret data over the network.
4. Scheming out a Multi-model Steganography system with good scalability for image and compare them with existing techniques.
5. To come out with a prototype model for secret communication of sensitive data in Government and Private sector, Satellite communication, Military application, Forensic application with better Scalability, PSNR and Time Efficiency over existing techniques.
5. EXISTING SYSTEM
For securing the sensitive visual information gray scale visual cryptography technique is presently used where the secret image is divided into shares, the shares are also called transparencies. The original secret image is retrieved on stacking shares together. The secret image is converted into monochrome image and then is split into two transparencies, which has a pair of pixels for every pixel in its original image. The pixels are shaded black and white based on the pixel of original image. If the original image pixel is dark (0/ ) then pixel in shares must be complementary i.e and the other
If it is white(1/ ) both should be or both .Based on this rule and using simple
algorithm on super imposing the shares or transparencies the original image is retrieved.
In steganography technique widely the data are hidden into image using Least Significant Bit (LSB) method. Where the data is stored in cover image by selecting a pixel and storing in its LSB. The pixel is selected by various techniques, like histogram , in which 2 bins are selected i.e pixel values and it is considered to hide data using LSB method. Similarly high density pixel, edges of the cover image, dark regions, blue regions in an image are targeted more. Since making change in pixel using LSB will not be easily identified and it is simple technique.
The following are the drawbacks the existing system suffers:
1. On applying existing visual cryptography technique to color image, the color information is lost in decrypted image.
2. On applying existing visual cryptography technique on color image the size of decrypted image i.e retrieved image will be doubled.
3. The clarity of the decrypted resultant image is very poor since the size is distorted.
4. In LSB based steganography method the attackers retrieve the secret data by comparing the pixel LSB of both stego image and the original image.
5. The size of the cover image required for a particular message image is 8 times more, thus has to increase the bandwidth .
6. PROPOSED SYSTEM
The New visual cryptography system for color images will overcome the above drawbacks of existing system, the color information is retained in decrypted image and the size of it is retained as of original image using Novel Random matrix pixel shuffling technique. So the decrypted image and shares contains color property without pixel expansion. The original image can also be decrypted or retrieved by considering k shares out of n i.e (k, n). The not all shares, but k among n shares are used to get original image.
In steganography technique, a Novel mask image system is proposed, in which the secret data is retrieved on placing the mask image on original image. For high secured, reliable and efficient data hiding system, the proposed New Visual Cryptography and steganography systems are combined with multi-modal approach to come out with a prototype model for secret communication of confidential data in real time applications like satellite communication, defense application, Forensic application. As shown in Figure 3, the secret data or image and cover image are considered. Along with the proposed multi-model approach the Novel Steganography and Visual cryptography is applied to transfer the secret data.
7. PROPOSED SYSTEM FLOW CHART
Figure 3: Proposed System Flow chart
The proposed system can be used in the following Applications:
• ATM transactions
• To provide secured authentication in online shopping payment
• Multi-biometrics authentication in bank locker system
• In Defense and Forensic area to transfer or communicate secret information over the network
• In Internet Voting System
• To Identify Phished Websites
• Using in Passport Verification System
• Copyright Protection, the mechanisms that prevent data, usually digital data, from being copied by insertion and analysis of watermarks.
8. CONCLUSION
A more scalable and efficient system to secure the secret data over communication channel is proposed. New visual cryptography technique for color images is proposed that creates color shares. Original image is retrieved with negligible distortion, by retaining the color information without pixel expansion and Novel Image steganography system for hiding information is proposed. The proposed Visual Cryptography and Steganography techniques are combined along with multi-model approach to achieve high secured system which conceals the messages in images is then transmitted over the network. The time efficiency is improved by parallel processing so that the proposed system can be used to the best in real time applications.
9. REFERENCES
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