Heesung Jun

Group-based public-key management for self-securing large mobile ad-hoc networks

For securing mobile ad-hoc networks, asymmetric key cryptosystem is one of effective technologies for encryption and authentication. However, for public-key distribution, the assumption about the availability of on-line trusted authorities or certificate repositories is unrealistic due to the very nature of ad-hoc networks. In this paper, a group-based public-key management system that allows users to generate public/private key pairs by themselves is proposed. In the proposed system, a group head issues certificates for group members and each node can perform authentication without requirement of on-line fixed trusted authorities. Taking self-securing approach, the proposal eliminates the problem of unrealistic assumption by introducing a localized trust model and suggesting an adaptive public-key distribution mechanism. Moreover, in the public-key distribution scheme, a solution for reducing overhead is proposed to adapt our system with the scalability of networks. Therefore, the system is suitable for any contemporary routing protocols in large mobile ad-hoc networks.

Design and implementation of digital filters for audio signal processing

An analog active filter do not provide a very sharp cut-off for both higher and lower frequency component, while a digital signal processor (DSP) using digital filter effectively reduces the unwanted higher or lower order frequency components within an audio signal. In this paper, we present the design and implementation of digital filters for audio signal. Experimental results show that digital filters including low-pass, high-pass, and band-pass effectively eliminate both low and high frequency components contained in human voice, providing high quality voice.

A Self-secure Routing Protocol for Large Mobile Ad hoc Networks

Securing mobile ad hoc networks is a nowadays emerging research topic. In this paper, we propose a self-secure routing protocol that is primarily based on public-key certificates which are provided locally and flexibly. Specifically, by taking self-securing approach, the proposed protocol makes use of a localized trust model which allows users to get certificates and to perform authentication without requirement of any on-line trusted third party. Compared to other securing routing protocols, our solution eliminates the unrealistic assumption about the availability of on-line trusted authorities or certificate repositories, thus, it can take advantage of public-key technology to prevent many types of attack from malicious nodes. Moreover, in the public-key distribution scheme, a solution for reducing overhead is proposed that makes our protocol adaptable to large mobile ad hoc networks.

Baleen Whale Sound Synthesis using a Modified Spectral Modeling

Spectral modeling synthesis (SMS) has been used as a powerful tool for musical sound modeling. This technique considers a sound as a combination of a deterministic plus a stochastic component. The deterministic component is represented by the series of sinusoids that are described by amplitude, frequency, and phase functions and the stochastic component is represented by a series of magnitude spectrum envelopes that functions as a time varying filter excited by white noise. These representations make it possible for a synthesized sound to attain all the perceptual characteristics of the original sound. However, sometimes considerable phase variations occur in the deterministic component by using the conventional SMS for the complex sound such as whale sounds when the partial frequencies in successive frames differ. This is because it utilizes the calculated phase to synthesize deterministic component of the sound. As a result, it does not provide a good spectrum matching between original and synthesized spectrum in higher frequency region. To overcome this problem, we propose a modified SMS that provides good spectrum matching of original and synthesized sound by calculating complex residual spectrum in frequency domain and utilizing original phase information to synthesize the deterministic component of the sound. Analysis and simulation results for synthesizing whale sounds suggest that the proposed method is comparable to the conventional SMS in both time and frequency domain. However, the proposed method outperforms the SMS in better spectrum matching.

AR-based Message Annotation System for Personalized Assistance

We propose an annotation system, which allows users moving on an environment to receive personalized messages that are generated by exploiting contextual information. In the system, the context is defined as an entity including user`s identity, location and time. Identity of user is a key data to enable personal aspect of generated message. For sensing the context, the proposed system uses AR(augmented reality) technology. Markers are attached to real objects for tracking user`s location. AR can provide an effective annotating method to enhance human`s perception and interaction abilities. The received message can be a virtual post-it or three-dimensional virtual model of object overlaid onto the real-world view. Experimental results show that the proposed system works well in real-time with high performance and it can be used as a mobile service for personalized messaging.

Audio Watermarking System using Replica Modulation Method

In this paper, we present an audio watermarking system based on replica modulation method (RMM). The system uses frequency-shift scheme to create a replica from an original signal. However, differing from previous works we use a part of the input signal to add the replica instead of the whole signal. The most significant part of the signal is extracted first and then RMM is applied to that part. The proposed method makes the system stronger against common audio signal processing such as noise addition or re-sampling. Besides, it has adjustable parameters which allow the system to be adaptable for various data sets. These parameters can be used to control the trade-off between imperceptibility and robustness. This kind of system has a simple design, high quality and good robustness. The more important thing is its strong security inherited from RMM which is immune from synchronization attacks. Also, we will show our implementation and discuss about the experimental results.

A pipelined augmented reality system

Performance is one of critical issues in augmented reality (AR) system. In this paper, we introduce a pipeline framework model used for AR system, referenced as pipelined augmented reality system. Pipelining exploits parallel at thread level and each critical process can run on a separate thread. Using pipelining in AR system, we can improve the performance of system significantly. We also use object-oriented concept to design and implement this pipeline framework. The evaluation result shows that the performance of the pipelined AR system is better than that of the normal AR system.

Applying Service-Oriented Architecture in AR-Based Annotation Message System

Augmented Reality provides an effective method to enhance humanpsilas perception and interaction by rendering and displaying 3D virtual objects overlaid in the real world view. It is a good way to display received annotation message visually in Annotation Message System. This paper proposes a new architecture for AR-Based Annotation Message System by applying service-oriented architecture, which is an extendible, interoperable, modular, and scalable software/system architectural model. We develop it and also implement with a specific case. Experimental results show that this architecture can work well in real time.

A personal locating system using the vision-based augmented reality

This paper describes the personal locating system in image sequence using a vision-based augmented reality technique which allows the user to navigate an unfamiliar and unknown place in an office environment. For identifying personal location in image sequences, the system uses a color histogram matching method and location model. The results are overplayed on the user’s view through AR technique. This system is applicable to guide an application.