Ratnakirti Roy

Secure key based image realization steganography

Steganography is the science of hiding crucial information in someinnocuous objects such that the mere existence of the hidden information is unidentifiable in human sight. Various unique methodologies have been implemented over time to hide information using steganography. In most of the methodologies the exact secret information is hidden inside the cover image in a way that it is completely unrecognizable. Thus, if the embedding mechanism is compromised, there is no way that the hidden message can remain unexposed. Security of the secret information can be enhanced if the actual secret message is not embedded in the cover image at all. In this paper a novel approach to image steganography through image realization has been proposed in which, rather than sending the actual secret information some mapping information of the secret information is embedded in the stego image. The actual realization of the secret information is secured using a multi layered secure pass key.

A secure image steganography technique with moderately higher significant bit embedding

Steganography is a process to hide secret data into a cover media in an imperceptible manner. In the spatial domain of image steganography, the most common technique is Least Significant Bit Replacement (LSBR). However, LSBR is extremely sensitive to compression attacks involving truncation of LSBs. As a possible solution to the drawback of the traditional LSBR scheme, this paper proposes an image steganography technique that embeds secret data in the moderately higher significant bits such as 4th or 5th bit of a pixel. The proposed method uses a color image as a cover and according to pixel values; three groups of pixels are maintained. These groups are used for selecting the candidate pixels for 4th or 5th bit embedding. It also implements an optimal pixel adjustment process (OPAP) to minimize the visual distortion due to embedding. In addition to the OPAP, a method for randomly dispersing the secret data bits is also implemented making it harder for an adversary to detect hidden information. The experimental results for proposed method showed high values for Peak Signal to Noise Ratio (PSNR) signifying High stego-image fidelity.

Cropping and Rotation Invariant Watermarking Scheme in the Spatial Domain

Digital Watermarking is an information hiding technique in which an identifying piece of information is embedded into a cover work so as to identify the ownership of some important information or document. It is widely used for enforcing copyright infringement protection for various types of digital data including images. In images, various watermarking techniques have been proposed over time. The watermarking techniques are often susceptible to geometric attacks such as rotation and cropping. This paper proposes an image watermarking scheme which uses the geometric properties of an image to ensure invariance of the watermark to rotation and cropping. It also incorporates a checksum based mechanism for tracking any distortion effect in the cover work. Efforts have been given to ensure that the proposed algorithm conforms to high Robustness and Fidelity which are the primary quality requirements for any Digital Watermarking system.

A DWT based steganography scheme with image block partitioning

Steganography is a branch of information hiding. It hides the existence of a secret message by embedding it in a cover media. In this paper, a new method for color image steganography is proposed in frequency domain where Discrete Wavelet Transform (DWT) of the cover image is used to differentiate high frequency and low frequency information of each pixel of the image. Proposed method hides secret bits in three higher frequency components making sure that the embedding impact on the cover image is minimum and not centralized in sensitivity domain. Experimental results reveal a good visual quality of the stego image with desirable steganalysis resisting characteristics.

Image realization steganography with LCS based mapping

Image Realization Steganography aims in devising techniques that realize a secret message from a cover image using a suitable cover-to-secret mapping with low embedding rates. This paper presents an Image Realization Steganography technique which maps a secret image as a Longest Common Subsequence of a given cover image. The cover image being a string of high degree of randomness and a very large length as compared to the secret image, the length of the LCS between them is expected to be close to the length of the binary string equivalent of the secret image. This enables the proposed technique to realize a secret image with very little or no modification of the cover. Experimental results validate this fact strongly. The results also indicate that any given cover image can be used to realize a secret image as large as itself thereby establishing the high hiding capacity of the technique.

High Capacity Image Steganography Based on Pixel Value Differencing and Pixel Value Sum

Steganography is the art of hiding information secretly inside a multimedia signal in such a way that its very existence is concealed. In this paper a new image steganography technique has been proposed which is based on the pixel value differencing and the pixel value sum of two consecutive pixels of a cover image. The proposed algorithm hides the secret data in the cover image by manipulating the difference or sum of the non-overlapping blocks of two consecutive pixels. This technique is an improvement over the Wu and Tsais PVD technique that is totally based on pixel value differencing. Experimental results validate that the proposed algorithm provides higher capacity than original PVD and produces a stego image having a good visual quality.

A map-based image steganography scheme for RGB images

Majority of research in steganography focuses on hiding the secret information into the cover directly. The payload can be more secured by not embedding the secret in the cover at all. Instead, a partial information about the secret may be embedded which can be used for later payload realisation. This typically appears analogous to random noise and cannot regenerate the payload without a key. Common approaches to achieve such information include pre-embedding payload encryption. However, simpler cover-secret map-based techniques can also be thought of where such information is generated with optimal resource utilisation. This paper proposes a map-based data hiding scheme in images through image realisation steganography. The proposed technique works for colour and grey images. It also incorporates a multi-stage decoding key and there have been efforts to ensure that the technique conforms to high fidelity of the stego image and performs decently against steganalysis attacks.

Image steganography with block entropy based segmentation and variable rate embedding

Steganography is the art and science of concealing information inside apparently innocuous covers like images, audio and video such that the very existence of the hidden message remains imperceptible to an adversary. Image steganography has numerous implementations developed over time. It is evident that certain areas in the image are more efficient for hiding data than the others. Such regions are called Regions of Interest. This paper proposes an object based image steganography technique that utilizes image entropy to segment smooth and textured areas in a cover image and then embed data with a variable data rate high efficiency embedding scheme. The method is shown to yield promising results in terms of stego-image fidelity and statistical imperceptibility.

Object Based Image Steganography with Pixel Polygon Tracing

The paper presents an object based image steganography technique which uses pixel polygonal area tracing in a cover image to select suitable pixels for embedding secret data. The polygon is generated using convex hull for specific selected image pixels and the distortion function is a hybrid between a high efficiency embedding scheme and LSB matching. The proposed technique is simple, yet effective. Experimental results show that the proposed method exhibits high fidelity of the stego-image and performs decently against well-known spatial domain steganalysis techniques for moderate payload capacity.

Watermarking through image geometry change tracking

Abstract Most of the digital image watermarking techniques are susceptible to geometric attacks such as cropping, rotation and scaling. These attacks are the easiest yet most successful in rendering the survival of watermark difficult. Such geometric operations alter the pixel orientation in the cover thereby rendering the watermark difficult to locate and extract. However, if the alterations produced by the geometric attacks such as scaling, cropping and rotation can be modeled in terms of the change in the image geometry, it is possible to relocate the watermark even after the original cover has suffered an attack. This paper contributes to the state of the art by proposing an image watermarking technique that attempts to model the attacks like cropping, scaling and rotation in terms of the image geometry. The proposed scheme is acceptably resistant to common geometric attacks and common image processing attacks. The watermark embedding is also done efficiently to offer resistance to image processing attacks. The watermark detection procedure is blind and key based, also not requiring the original cover work for watermark extraction. Efforts have been given to ensure that the proposed scheme conforms to robustness against attacks and exhibits high visual fidelity of the watermarked cover.