Sungwon Sohn

Chalcogenide thin-film transistors using oxygenated n-type and p-type phase change materials

A technique for chalcogenide thin-film transistors (ChG-TFT) using oxygenated (Ox) n-type and p-type phase change materials is developed. By the oxygen doping into Ge2Sb2Te5 (GST) in a range of 10%–35%, the oxygen impurities induced by destabilization of the electron killers in GST and resultantly n-type Ox-GST was realized. For a p-type Ox-GST, by GeTe deposition with GeTe/Ox-GST ratio more than 0.3 and subsequent thermal diffusion, the diffused film showed the p-type conductivity. With n-type and p-type Ox-GST films, the doped ChG-TFTs were developed. The rectification ratio was ∼103 at +5 V, and was increased by the p-n junction structure.A technique for chalcogenide thin-film transistors (ChG-TFT) using oxygenated (Ox) n-type and p-type phase change materials is developed. By the oxygen doping into Ge2Sb2Te5 (GST) in a range of 10%–35%, the oxygen impurities induced by destabilization of the electron killers in GST and resultantly n-type Ox-GST was realized. For a p-type Ox-GST, by GeTe deposition with GeTe/Ox-GST ratio more than 0.3 and subsequent thermal diffusion, the diffused film showed the p-type conductivity. With n-type and p-type Ox-GST films, the doped ChG-TFTs were developed. The rectification ratio was ∼103 at +5 V, and was increased by the p-n junction structure.

Design of an Extended Architecture for Secure Low-Cost 900MHz UHF Mobile RFID Systems

The mobile RFID (radio frequency identification) is a technology for developing a RFID reader embedded in a mobile terminal and providing various application services over wireless networks. Various security issues-Inter domain security, privacy, authentication, E2E (end-to-end) security, and untraceability etc.-need to be addressed before the widespread use of mobile RFID. Low cost mobile RFID systems are increasingly being deployed in industry and m-commerce. These contactless devices have raised public concern regarding violation of privacy and information security. There is a growing need in the mobile RFID community to discover and develop techniques and methods to overcome several problems posed by the above-mentioned concerns. This paper presents proposals on feasible security mechanisms for low-cost mobile RFID systems and analyses them from both security and privacy points of view

Certificate validation service using XKMS for computational grid

A computational grid is a hardware and software infrastructure capable of providing dependable, consistent, pervasive, and inexpensive access to high-end computational resource. There are many ways to access the resources of a computational grid, each with unique security requirements and implications for both the resource user and the resource provider. Current Grid security Infrastructure using PKI based on SSO. But open grid service Security Infrastructure in Global Grid Forum(GGF) will extend use of grid system or services up to business area using XML web services security technology. This paper describes a novel security approach on open grid service to validate certificate based on current globus toolkit environment using XKMS(XML Key Management Specification) and SAML(Security Assertion Markup Language), XACML(extensible Access Control Markup Language) in XML security.

XML-signcryption based LBS security protocol acceleration methods in mobile distributed computing

This paper describes the open security architecture for LBS (Location- based Services) platform ensuring interoperability among the wireless networks and various location-based application services and the functional security requirements for the LBS platform. The goal of this paper is to investigate how well the most limited wireless devices can make use of LBS security services. In this paper, we suggest security acceleration methods for high speed open LBS using XML signcryption mechanism. And proposed secure LBS security protocols allows a client to offload mobile certificate handling to the server and to enable the central administration of privacy polices. The idea is to create a signcryption technique for software based XML signature acceleration.

Certificate Validation Scheme of Open Grid Service Usage XKMS

Current Grid Security Infrastructure using PKI based on SSO. Trust is hard to establish in a service-oriented grid architecture because of the need to support end user SSO and dynamic transient service. Open Grid Service (OGS) Security Infrastructure in Global Grid Forum will extend use of Grid system or services up to business area using XML Web Service security technology. This paper describes a novel security approach on Open Grid Service to validate certificate based on current Globus Toolkit environment using XKMS and SAML, XACML in XML Security. Our security model is based on XKMS, an implementation of the Java component and international standard specification.

Kernel-level intrusion detection system for minimum packet loss

Supporting dynamic rule change with minimum packet loss is one of the key issues for intrusion detection. To detect intrusion, in general, Intrusion Detection System(IDS) has a copy step where P packet is captured at kernel level and it is used for detection in user level. While doing this job, the next packet cannot be captured because this procedure isn¿t finished yet. This paper proposes the Kernel-level Intrusion Detection System(KIDS) which can detect various network attacks with minimum packet loss. This system is executed in kernel as a kernel program, and can detect intrusion at kernel level without copy step. Dynamic rule change is done quickly through appending and setting a delete mark operation. After this work, it is not needed to reboot a kernel and new type of network attack can be detected easily. With the help of this dynamic rule change, waiting time of detection process is minimized and its job can be continued as quickly as possible. Due to these features, the packet loss is greatly reduced.

In situ measurement of superoxide and hydroxyl radicals by frequency mixing detection technique

Frequency mixing magnetic detection (FMMD) was used to detect superoxide from hypoxanthine and xanthine reaction and to detect hydroxyl radical from the Fenton reaction. FMMD was also applied to measure the reactive oxygen species (ROS) level released from microglial cells. We could assess the formation and extinction of the free radicals without a spin trap reagent. The FMMD signal amplitude scaled with the concentration of the radicals. It was verified that no signals are obtained from the substrates and reagents. Based on the observations and on previous research, we suggest that the FMMD signals originate from superoxide and hydroxyl radicals, indicating that FMMD can be used to detect O-centered radicals. Subsequent analysis of free radicals generated from living microglial cells showed that there were significant differences between the activated microglial cells and resting ones. The results of this research are promising regarding the applications of FMMD for in situ measurement of free radicals from various sources, including the cell.

Generation of audible sound with ultrasonic signals through the human body

This paper presents an innovative hearing system. The hearing system generates audible sound in the ears without any receivers, and no one can hear the generated sound except the user. The theory for generating audible sound is based on a self-demodulation effect which arises from the nonlinearity of the transmission medium. The nonlinear acoustics of the human body allow ultrasonic waves to interact in the transmission medium. When two ultrasonic waves with different frequencies are transmitted through the human body, an audio signal at the difference frequency of two waves is produced in the ears due to the self-demodulation effect.

XML key management system for Web-based business application

XML is a global standard for the Internet and e-business, and its use is growing in proportion to the spreading speed of e-commerce. Thus, a policy for providing a safer security service for exchanging e-documents within e-commerce is necessary. XKMS (XML key management specification), one of XMLs security specifications, defines the protocol for distributing and registering public keys for verifying digital signatures and enciphering e-documents of e-commerce applications with various and complicated functions. This paper presents an XKMS-based key management system architecture and a service model using Java crypto technologies and XML security mechanisms.

Development of XKMS-Based Service Component for Using PKI in XML Web Services Environment

The emerging Web Services technology provides a systematic and standard-based approach to enable application-to-application integration. In this paper, we propose XKMS(XML Key Management Specification)-based key management service model and design protocol component based on standard specification. Also describes the analysis and security method of key management service for secure global XML Web Services, paying attention to the features of XML based security service. This service model offers the security construction guideline for future e-business and global XML Web Services frameworks.