Gabriel Bugar

A novel method of image steganography in DWT domain

In this paper, we present a novel steganographic method for embedding of secret data in still grayscale image. In order to provide large capacity of the secret data while maintaining good visual quality of stego-image, the embedding process is performed in transform domain of Discrete Wavelet transform (DWT) by modifying of transform coefficients in an appropriate manner. In addition, the proposed method do not require original image for successful extraction of the secret information. The experimental results show that the proposed method provides good capacity and excellent image quality.

Steganography systems by using CDMA techniques

In this paper, we present a novel method called Code Book in steganography system based on CDMA (Code Division Multiple Access) techniques having regard to perceptibility of stego-image. These techniques and their variations are widely used in radio telecommunication systems. As it will be shown later, aptly imposed features of CDMA techniques are in consonance with imperatives claimed upon steganography systems.

A novel approach for image steganalysis

Since JPEG images have been widely used in our daily life, the steganalysis for JPEG images becomes very important and significant. The Article addresses steganalysis in static images based on DCT transformed region, able to recognize the most popular steganography algorithms occurring on the Internet. We propose a new steganalysis method, where statistical properties of the image are explored, regardless the embedding procedure employed. The feature set used for classification of images consists of 285 statistical features. Experimental results show that in comparing with the universal steganalysis method for JPEG stego images, our method improves detection of widely used steganographic method in detection process, which provides observable differences in investigation performance.

Information hiding using pseudo-random number sequences with error correction

In this paper, we present a novel method of steganography system based on CDMA (Code Division Multiple Access) approach having regard to perceptibility of stego-image. Also additional extraction algorithms were designed due to enhancing of secret message decomposition. As it will be shown later, aptly imposed features of CDMA techniques are in consonance with imperatives claimed upon steganography systems.

Steganography in data networks based on PDU retransmission

The aim of this work is to present a real and useful application of steganography systems in data communication networks. Different from all the previous work analyzing the traditional steganography system, we introduce the possibility of the TCP protocol mechanism usage in steganography based on intentionally triggered protocol data unit (PDU) retransmission. It describes how to create a subliminal channel in the network and its usage for steganography purposes, so called network-based steganography, which is relatively a new research object in the field of information hiding. We analyzed the way of creating a hidden steganography channel via PDU retransmission in a real network. The achieved results of the proposed method are in practical part and in the end the recovered qualitative benefits of simulations are situated.

A novel block-based data hiding scheme in SVD-DCT composite domain

This paper presents a robust block-based watermarking scheme for multimedia copyright protection. In this work, we used benefits of domain combination of Singular Value Decomposition (SVD) and Discrete Cosine Transformation (DCT). Our aim was to utilize the favorable properties of both transformations to design of a unique and useful transformation standard algorithm for embedding watermarks into cover data. The proposed watermarking scheme is verified from the point of view of imperceptibility expressed by objective quality measure PSNR (Peak Signal-to-Noise Ratio) and robustness to different types of removal (JPEG compression, Gaussian filtering, Sharpening) and geometric attacks (Scaling and Rotating).

Spatial Real-Time Price Competition in the Dynamic Spectrum Access Markets.

We present the agent-based model of the real-time spectrum trading market. Real-time means that the frequency spectrum is allocated to the operators in real-time and thus, the capacities of the operators are dynamically varying. The agent-based model consists of the two levels. The first level (the wholesale market) deals with the spectrum distribution towards the operators, where the operators compete for the spectrum resources. The second level (the retail market) presents the place where the operators compete with each-other to provide their services to the end-users. In our model, the operators are assumed to be heterogeneous in terms of the quality of service (QoS) perception. The heterogeneity of the operators exists due to the different placement of their base-stations (BTSs) in the investigated region. The BTS in the middle of the region is naturally favored, because of the unique spectral efficiency it provides to the end-users. We numerically analyze the volumes of the frequency spectra purchased by the operators, average revenue and the retail price of the operators under the consideration of three different pricing mechanisms.

Edwards curve addition and doubling formula analysis for effective parallel decomposition

The Elliptic Curve Cryptosystem is an emerging alternative for traditional Public-Key Cryptosystem like RSA, DSA and DH. It provides the highest strength-per-bit of any cryptosystem known today with smaller key sizes resulting in faster computations, lower power consumption and memory. It also provides a methodology for obtaining high-speed, efficient and scalable implementation of protocols for authentication. The objective is to give the reader an overview on efficient addition and doubling formulas of Edwards curves together with analysis and effective parallel decomposition of these formulas. Practical analysis is provided with implementation consideration.

Robust spread spectrum watermarking system in video

In this paper we propose robust watermarking schema for video files based on spread spectrum theory. The main concept relies on utilization of time as temporal dimension for spreading of watermark bits that are assigned to video frames. The second level spreading that is impartial to first level, uses different set of PN sequences within the video frames what allows to utilize multiple watermarking methods designed for still images simultaneously. Two dimensional spread spectrum watermarking framework allows acquiring a high level of robustness with desired imperceptibility of hidden watermark. Two independent embedding methods LSB and DCT were tested during embedding as representative techniques of different embedding domain. The presented results show that proposed watermarking schema is able to withstand intentional attacks. The proposed system is robust and adaptive to recent and newly developed embedding technique, which could provide a requisite of robustness and protection against copyright infringement.