Vinay Kumar

A data structure for graph to facilitate hiding of information in a graph's segments – a graph theoretic approach to steganography

In this paper, we present a data structure that is suitable for graph representation that can be used as a cover object in steganography. Steganography is a science of hiding information with the purpose of making the information unreadable by a third party. The information is placed in the cover object in such a way that the distortion introduced in the cover object is as minimal as possible and to the extent not recognisable by the human eye. To accomplish the task, redundancy in the representation of the cover object is identified before placing the information in it. There exists a number of data structure for graph representation e.g., adjacency matrix, incidence matrix, adjacency list, etc. These classical data structures allow little scope of finding redundancy in graph. The data structure presented in this paper is file based. It divides a graph into three components: node, segment and intermediate points that constitute a segment. Under the scheme, only planar graph is being considered to maintain clarity in spatial representation of a graph. The presented data structure is aimed to facilitate graph theoretic approach to steganography.

Investigation of oxygen impurity transport using the O4+ visible spectral line in the Aditya tokamak

Intense visible lines from Be-like oxygen impurity are routinely observed in the Aditya tokamak. The spatial profile of brightness of a Be-like oxygen spectral line (2p3p 3D3?2p3d 3F4) at 650.024?nm is used to investigate oxygen impurity transport in typical discharges of the Aditya tokamak. A 1.0?m multi-track spectrometer (Czerny?Turner) capable of simultaneous measurements from eight lines of sight is used to obtain the radial profile of brightness of O4+ spectral emission. The emissivity profile of O4+ spectral emission is obtained from the spatial profile of brightness using an Abel-like matrix inversion. The oxygen transport coefficients are determined by reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional empirical impurity transport code, STRAHL. Much higher values of the diffusion coefficient compared with the neo-classical values are observed in both the high magnetic field edge region and the low magnetic field edge region of typical Aditya ohmic plasmas, which seems to be due to fluctuation-induced transport. The diffusion coefficient at the limiter radius in the low-field (outboard) region is typically ? twice as high as that at the limiter radius in the high-field (inboard) region.

Hamiltonian graph approach to steganography

A Hamiltonian graph approach is presented in this paper to ensure privacy and secrecy of a crucial secret message that is normally short and precise. A short secret message is treated as stream of bits. Each bit is compared with a functional output of a portion of cover image. The cover is partitioned into as many portions as there are bits in the message. If the bit in the message is equal to the functional output of the corresponding portion of cover, then nothing needs to be done. In case of inequality, a node of graph is created. Then adjacency among nodes is found so that exchange of colour components of pixels according to the direction of traversal in a Hamiltonian cycle makes the functional output of the portion equal to the corresponding bit. Whenever a node is not found to be adjacent to any other node, then the corresponding bit is spread over in the portion in such a way that net effect on the colour components of pixel remains < 0.01. The approach helps in retaining vital statistics of the cover in the stego.

Graph Theoretic Approach to Steganography to Secure Message Digest

ABSTRACT Recent attacks presented for Secure Hash Algorithm -1 (SHA -1) and Message Digest 5 (MD5) have drawn attention of researchers and information security managers to look for a way to secure it. Visibility of information, whether encrypted or not, provides worst kind of vulnerability. Possibility of finding collisions by attackers can be made practically infeasible if statistics related to message digest is denied by hiding the digest. Complicating the process of digest creation may solve the problem temporarily. However it can not discourage the hackers from doing so. If the created digest is hidden in some cover object, it makes difficult for hackers to collect statistics that helps in finding possible collisions. In this paper, we introduce a graph theoretic approach to steganography to hide digest into extra bytes of a Bit Map Pixel (BMP) file. This approach can also be used for securing any fixed length keys during key exchange in Public Key Infrastructure (PKI).

Watermarking digital vector map using graph theoretic approach

Similar to any digital dataset, a digital map is also vulnerable to modification, deliberate alteration and copyright violation. A map is a visual representation of a geographical area that is digitally stored in either raster or vector forms. Vector map is preferred over raster for both space optimization and quick processing time. Digest concept used for message authentication is extended to digitally watermark a digital map. The map digest triplet ( , and ) is generated using various features of a digital map, supplier code and customer code. The approach computes two 160-bit hash values using secured hash algorithm (SHA1)and one 128-bit digest using message digest (MD5) algorithm. These two hash values of 160 bit and one digest of 128 bit are then embedded into a sequence of nodes of the map using graph theoretic approach in such a way that any alteration in the map alters the sub-graph. The sub-graph is the watermark. There are three watermarks.

Hiding Message in Map Along Pre-Hamiltonian Path

In this paper, an algorithm to embed information in a map along Hamiltonian path is presented. A file based data structure in which a graph is treated as a composition of three components, node, segment and intermediate points that constitute a segment, is used to store a graph. In a map with N nodes, each node can represent ?log2N? bits from message bit strings. Any bits = 0 from message between bit strings represented by adjacent nodes are embedded in a segment. In the case of a multi graph, a segment is selected based on the last two bits in the nodes. A pre Hamiltonian path is determined in the map starting from node represented by the first ?log2N? bits from message string to the last bit string ?log2N?. The method is tested on different maps and messages of different sizes and robust results have been observed. Retrieval is based on the key S, |m|, ? and traversing along the pre Hamiltonian path starting from node S.

Improvement of Plasma Performance with Lithium Wall Conditioning in Aditya Tokamak

Lithiumization of the vacuum vessel wall of the Aditya tokamak using a lithium rod exposed to glow discharge cleaning plasma has been done to understand its effect on plasma performance. After the Li-coating, an increment of ~100 eV in plasma electron temperature has been observed in most of the discharges compared to discharges without Li coating, and the shot reproducibility is considerably improved. Detailed studies of impurity behaviour and hydrogen recycling are made in the Li coated discharges by observing spectral lines of hydrogen, carbon, and oxygen in the visible region using optical fiber, an interference filter, and PMT based systems. A large reduction in O I signal (up to ~40% to 50%) and a 20% to 30% decrease of Hα signal indicate significant reduction of wall recycling. Furthermore, VUV emissions from O V and Fe XV monitored by a grazing incidence monochromator also show the reduction. Lower Fe XV emission indicates the declined impurity penetration to the core plasma in the Li coated discharges. Significant increase of the particle and energy confinement times and the reduction of Zeff of the plasma certainly indicate the improved plasma parameters in the Aditya tokamak after lithium wall conditioning.

Comparison of Different Mapping Techniques for Classifying Hyperspectral Data

Hyperion is a space borne sensor which provides powerful tool in discriminating land cover features including urban area and in preparation of urban maps. It gives hyperspectral images in 242 bands within 400xa0nm to 2,500xa0nm wavelength range with 10xa0nm band-width. The Hyperion image in raw form is badly affected with several atmospheric effects which cause haziness. In this study hyperspectral image is atmospherically corrected by using FLAASH model of ENVI. After atmospheric correction the urban area was mapped using the spectral endmember collected by the procedure which includes minimum noise fraction (MNF), pixel purity index (PPI) and n-dimensional visualization in ENVI software. The aim of this study is to map the urban area using several mapping techniques such as Spectral Angle Mapper (SAM), Mixture Tune Matched Filtering (MTMF) and Linear Spectral Unmixing. The urban land covers displayed noticeable differences from one another in the spectral responses in the Hyperion image. The overall accuracy of the SAM classified map was 89.41%, which indicated good potential of Hyperion image for Classification. Use of the other approaches, linear spectral unmixing and MTMF have improved the classification results.

ALOS PALSAR and Hyperion Data Fusion for Land Use Land Cover Feature Extraction

Detailed and enhanced land use land cover (LULC) feature extraction is possible by merging the information extracted from two different sensors of different capability. In this study different pixel level image fusion algorithms (PCA, Brovey, Multiplicative, Wavelet and combination of PCA & IHS) are used for integrating the derived information like texture, roughness, polarization from microwave data and high spectral information from hyperspectral data. Span image which is total intensity image generated from Advanced Land observing Satellite-Phase array L-band SAR (ALOS-PALSAR) quad polarization data and EO-1 Hyperion data (242 spectral bands) were used for fusion. Overall PCA fused images had shown better result than other fusion techniques used in this study. However, Brovey fusion method was found good for differentiating urban features. Classification using support vector machines was conducted for classifying Hyperion, ALOS PALSAR and fused images. It was observed that overall classification accuracy and kappa coefficient with PCA fused images was relatively better than other fusion techniques as it was able to discriminate various LULC features more clearly.

Data Hiding Method Based on Inter-Block Difference in Eight Queens Solutions and LSB Substitution

Data hiding is an emerging field of research for secure data transmission over internet, ensuring ownership identification and copyright protection. A couple of techniques have been proposed based on pixel value differencing PVD and eight queens solutions. In this paper, a new data hiding method based on inter-block difference in eight queens solutions is presented. The result of inter-block difference is XORED with ASCII code of character from the message and the resultant value is embedded in LSB position. The presented approach is more efficient and it provides a more capacity with good imperceptibility. The approach supports different digital image file formats such as bmp, png and tiff.