Sunil Kumar Muttoo

Distortionless Data Hiding Based on Slantlet Transform

In this paper we present a distortionless data hiding technique based on wavelet-like transform, known as Slantlet Transform (SLT). The proposed algorithm first encodes the original message using the encoder, T-codes. T-codes have shown to be more robust than the best known variable-length codes, Huffman codes. T-codes have a well-explained resyhchronization mechanism which leads to fast and reliable resynchronization. The secret data is then embedded in the high frequency sub-bands, viz., HH, HL and LH which are obtained by applying Slantlet transform to the cover-image. We use two steganography algorithms, viz., LSB algorithm and Thresholding algorithm for embedding data in the image. We show further that the original image can also be recovered from stego-image after the hidden data is extracted from it. It is known that SLT is a better candidate for signal compression compared to the DWT based scheme and it can provide better time localization. Experimental results have confirmed that the proposed algorithm yields better imperceptibility for the stego-images than the conventional DWT based scheme in case of low embedding rate and yields acceptable results for high embedding rate as well.

A dynamic reputation system with built-in attack resilience to safeguard buyers in e-market

Reputation systems aim to reduce the risk of loss due to untrustworthy participants by providing a mechanism for establishing trustworthiness between mutually unknown online entities in an information asymmetric e-market. These systems encourage honest behavior and discourage malicious behavior of buyer and seller agents by laying a foundation for security and stability in the e-market. However, the success of a reputation system depends on its built-in resilience capabilities to foil various attacks. This paper focuses on how to safeguard buyers from dishonest sellers and advisors by incorporating an attack resilient reputation computation methodology. The objectives of the proposed dynamic reputation system in the distributed environment are to reduce the incentive for behaving dishonestly, and to minimize harm in case of attacks by dishonest participants with the inherent purpose of improving the quality of services in the e-market.

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.

A note on Reed-Muller codes☆

Abstract In this paper we study linear codes that are obtained by annexing some vectors to the basis vectors of a Reed-Muller code of order r.

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).

Approaches for Web Spam Detection

Spam is a major threat to web security. The web of trust is being abused by the spammers through their ever evolving new tactics for their personal gains. In fact, there is a long chain of spammers who are running huge business campaigns under the web. Spam causes underutilization of search engine resources and creates dissatisfaction among web community. Web Security being a prime challenge for search engines has motivated the researchers in academia and industry to devise new techniques for web spam detection. In this paper we present a comprehensive survey of techniques for detection of web spam and discuss their applicability and performance in various scenarios where they outperformed the others. We have categorized web spam detection with the primary focus on the approaches used for spam detection. The paper also gives the possible directions for future work.

Image Steganography Based on Wavelet Families

Image Steganography Based on Wavelet Families Wavelet transforms are considered to be an ideal domain for image compression and transmission. The new generation still image compression standard JPEG2000 uses the bi-orthogonal CDF 5/3 wavelet (also called the CDF (2, 2) wavelet) for lossless compression and a CDF 9/7 wavelet for lossy compression. There are several known wavelet families such as Daubechies, Coiflet, Symlet, CDF, etc. The problem of selecting a suitable wavelet for signal and image processing has always challenged the researchers. The conventional wavelet filters often have floating point coefficients and couldn’t realize the lossless reconstruction. The second generation wavelet transforms are based on lifting scheme and they map integers to integers. Thus they realize the lossless compression of image data with minimal memory usage and low computational complexity.

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.