Christian Krätzer

Design and evaluation of steganography for voice-over-IP

According to former results from (Dittmann et al., 2005) in this paper we summarize the design principles from the general approach and introduce extended experimental test results of a voice-over-IP (VoIP) framework including a steganographic channel based on (Dittmann et al., 2005), (Dittmann and Hesse, 2004), (Kraetzer et al., 2006) and (Vogel et al., 2006). We show that using this framework it is largely secure to transmit hidden messages during a VoIP session and demonstrate results with respect to perceptibility for music and speech data

WLAN steganography: a first practical review

Two different approaches for constructing a steganographic channel in an IEEE 802.11 (WLAN) network are introduced in this paper. First test results on the reliability, undetectability and capacity of a prototypical implementation of both approaches are described and discussed.

Extending the Clark-Wilson Security Model for Digital Long-Term Preservation Use-cases

A continuously growing amount of information of today exists not only in digital form but were actually born-digital. These informations need be preserved as they are part of our cultural and scientific heritage or because of legal requirements. As many of these information are born-digital they have no analog origin, and cannot be preserved by traditional means without losing their original representation. Thus digital long-term preservation becomes continuously important and is tackled by several international and national projects like the US National Digital Information Infrastructure and Preservation Program [1], the German NESTOR project [2] and the EU FP7 SHAMAN Integrated Project [3]. In digital long-term preservation the integrity and authenticity of the preserved information is of great importance and a challenging task considering the requirement to enforce both security aspects over a long time often assumed to be at least 100 years. Therefore in a previous work [4] we showed the general feasibility of the Clark-Wilson security model [5] for digital long-term preservation in combination with a syntactic and semantic verification approach [6] to tackle these issues. In this work we do a more detailed investigation and show exemplarily the influence of the application of such a security model on the use cases and roles of a digital long-term preservation environment. Our goals is a scalable security model - i.e. no fixed limitations of usable operations, users and objects - for mainly preserving integrity of objects but also ensuring authenticity.

Nested Object Watermarking : Transparency and Capacity Evaluation

Annotation watermarking (also called caption or illustration watermarking) is a specific application of image watermarking, where supplementary information is embedded directly in the media, linking it to media content, whereby it is not get separated from the media by non-malicious processing steps like image cropping or non-lossy compression. Nested object annotation watermarking (NOAWM) was recently introduced as a specialization within annotation watermarking, for embedding hierarchical object relations in photographic images. In earlier work, several techniques for NOAWM have been suggested and have shown some domain-specific problems with respect to transparency (i.e. preciseness of annotation regions) and robustness (i.e. synchronization problems due to high density, multiple watermarking), which is addressed in this paper. A first contribution of this paper is therefore proposed a theoretical framework to characterize requirements and properties of previous art and suggest a classification of known NOAWM schemes. The second aspect is the study of one specific transparency aspect, the preciseness of the spatial annotations preserved by NOAWM schemes, based on a new area-based quality measurement. Finally, the synchronization problems reported from earlier works is addressed. One possible solution is to use content-specific features of the image to support synchronization. We discuss various theoretical approaches based on for example visual hashes and image contouring and present experimental results.

A Hierarchical Model for the Description of Internet-Based Communication

With this paper we aim to support network traffic management and incident management processes. Hence this paper introduces a model to classify different types of internet-based communication and to establish homogenous representations for various forms of internet-based communication. To achieve these aims an approach to project different types of communications onto a comparable template is presented. This hierarchical approach for the classification of electronic communications is both exhaustive (in the sense of considered types of internet-based communication) and expandable (in terms of the level of granularity of the performed communication behaviour modelling as well as the corresponding data modelling).

Statistical effects of selected noise characteristics on speaker recognition in automotive environments: a first ANOVA-based investigation

A statistical analysis using the univariate, multifactorial analysis of variance (ANOVA) is used in this paper to investigate the impact of selected noise characteristics (here a 4-factorial design: amplitude, complexity, harmony and fundamental frequency) to speech signals and consecutively to the detection performance in speaker recognition systems (exemplarily used here: the BioSecure reference system ALIZE) in automotive application scenarios. An application scenario specific set of noise signals is recorded and generated and used to evaluate the influence of the noise characteristics. The results show that especially the amplitude and the fundamental frequency show a significant impact (p-values < 0.01), which is completely independent of the features used in the speaker recognition system. The two other characteristics (complexity and harmony) show much less significant impacts (p-values >0.5).

FirstAidAssistanceSystem (FAAS): improvement of first aid measures using Car2Car-communication technology

This works goal is the enhancement of first aid measures directly after car accidents by calling suited first aiders via Car-to-Car (C2C) communication and to assist them providing detailed multimedia support instructions. Our concept combines upcoming C2C communication technologies with established technology, in particular GPS and GSM. After a collision, the proposed FirstAidAssistanceSystem (FAAS) sends a broadcast message using C2C technology according to the IEEE 802.11p standard. All nearby cars (as potential first aiders) are located and at least one nearest candidate (we suggest 3-5) driving towards the accident scene is chosen and notified as first aider. A support guide on his multipurpose display (e.g. the navigation system) provides first aiders with detailed instructions and illustrative tutorials. The paper presents our concept in detail with a discussion of practical evaluation criteria and an introduction of a first test implementation.