Vassilis E. Fotopoulos

Medical image authentication and self-correction through an adaptive reversible watermarking technique

With the advent of Information Technology in the medical world, various radiological modalities produce a variety of digital medical files most often datasets and images. These files as any digital asset should be protected from unwanted modification of their contents, especially as they contain vital medical information. Thus their protection and authentication seems of great importance and this need will rise along with the future standardization of exchange of data between hospitals or between patients and doctors. Watermarking, a technique first introduced for multimedia files, provides a method for authentication and protection and has been recently applied to medical images. In this paper, we propose a novel watermarking technique where the region of non-interest (RONI) of medical Magnetic Resonance Imaging (MRI) images, is used to embed the region of interest (ROI). In this way, any tampering attempt, not only will be detected, but also the image could be self-restored, back to its previous, ldquooriginalrdquo form by extracting the ROI from the RONI.

An 8/spl times/8-block based motion estimation using Kalman filter

It is now quite common in the pel-recursive approaches for motion estimation, to find applications of the Kalman filtering technique both in time and frequency domains. In the block-based approach, very few approaches are available of this technique to refine the estimation of motion vectors resulting from fast algorithms such as the three step on a 16/spl times/16-block basis. This paper proposes an 8/spl times/8-block based motion estimation which uses the Kalman filtering technique to improve the motion estimates resulting from both the three step algorithm and the previous 16/spl times/16-block based Kalman application of Kuo et al. (1996). The state-space representation uses a first order auto-regressive model. Comparative results obtained for different classes of video sequences are presented.

Hybrid watermarking based on chaos and histogram modification

A hybrid watermarking scheme for authentication is presented, which demonstrates robustness against various attacks. Due to the different nature of filtering and geometrical attacks, two different watermarks are used in this scheme. The first one is embedded in frequency domain combined with a chaotic function and is based on the correlation method. The second watermark is embedded in luminosity histogram of the image. In this way, this hybrid watermarking scheme combines the robustness of chaotic domain against filtering, noise and compression attacks with the robustness of histogram domain against geometrical attacks.

Improved watermark detection based on similarity diagrams

A great number of digital watermarking approaches do exist, but it seems that transform domain watermarking dominates the field. The detection of such schemes is based on thresholds extracted by statistic rules on which the method relies. In this work, we propose an improved detector for such techniques. It extends the traditional schemes by taking into account the similarity diagrams that are widely used until now as an evidence of the watermarks existence and uniqueness.

Transform domain watermarking: adaptive selection of the watermark’s position and length

Transform domain methods have dominated the watermarking field from its early stages. In these methods some coefficients are selected and modified according to certain rules. The two most important numbers in this process are the length and the position of the watermark. These are usually heuristically chosen. In order to handle this problem, an adaptive scheme for the selection of the proper coefficients is analysed in the present communication.

Data hiding based on image texture classification

In this paper, a new pattern-based fragile, semi-blind, spatial domain data hiding scheme is proposed. The Local Binary Pattern texture classification approach is used, in order to transparently and securely embed secret data into an image. Pixel values are modified in such a way that the texture satisfies the message requirements. The method is thoroughly studied and compared to other techniques in spatial domain in terms of capacity and image quality. The scheme performs well in images with smooth areas and can be used for authentication, tamper proofing, and secret communications.

Decentralising the Digital Rights Management Value Chain by means of Distributed License Catalogues

Digital Rights Management (DRM) systems’ interoperability is becoming one of the main obstacles for their wider adoption, especially from medium and small size users. Interoperability issues affect, among others, the management of content usage rules by third parties (authorities) and the automation of licensing procedures upon the purchase of digital content. The fundamental question of who is handling content licenses in the national or global DRM value chain is complex, with business, social and technological extensions. In this paper, we discuss current trends in DRM systems technology and business modelling and briefly present a proposal for handling digital content licensing, Distributed License Catalogues (DLCs). The DLC concept, borrowed from web engineering, makes available (“advertises”) content or services concerning DRM functionalities, enabling multi-party DRM eco-systems.

Protecting intellectual property rights and the JPEG2000 coding standard

The ever-increasing use of the Internet and file sharing applications based on Peer to Peer networks has alarmed content authors, providers and resellers of digital content. Techniques proposed for protecting digital media include watermarking, use of metadata and self-protection and self-authentication. In this paper we review the most important of these methods and analyse their potential use in Digital Rights Management systems. The main focus is on IPR management through watermarking for digital images coded with the new and a lot promising compression standard: JPEG2000.

Gabor transform domain watermarking

The transform domain is the most commonly used space for watermarking applications. Most of the common frequency transforms have been used for this purpose. We investigate the use of the Gabor (1946) transform in traditional watermarking schemes. A casting method and detection results are thoroughly examined. It seems that traditional detection thresholds are not applicable in this transform, thus a modified approach is employed to overcome this problem. Experimental results are quite encouraging.

A New Approach to Gradual Video Transition Detection

In this paper the problem of shot boundary detection for gradual transitions within video sequences is treated using statistical tests in conjunction with the Iterative Self Organizing Data Analysis (ISODATA) classification algorithm for consecutive video frames. The confusion matrix from the classification results is formed in order to calculate the kappa coefficient and from this to identify the transition. Experimental and comparative results with recently proposed methods are promising.