다중 레벨 Atomicity를 기반으로 한 객체지향 데이타베이스 트렌젝션 모델

오희국(Heekuck Oh),최동시(Dongsee Choi) 한국정보과학회 1993 한국정보과학회 학술발표논문집 Vol.20 No.2

객체지향 데이타베이스는 종래의 관계형 데이타베이스로는 처리가 용이하지 않은 CAD나 멀티미디어와 같이 복잡한 Hierarchy 구조를 가진 어플리케이션들에 대한 적절한 대안으로 인식되고 있다. 이러한 어플리케이션 내의 트랜젝션들은 종종 장시간 지속되는 협동운영을 요구한다. 그러나 객체지향 데이타들의 특성인 클래스와 클래스 구성 체계 그리고 상속으로 부터 발생하는 복잡성으로 인해 종래의 Serializability에 의존한 Correctness Criteria는 더 이상 유효하지 못하다. 본 논문은 이 문제에 대한 부분적인 해결책으로 객체지향 데이타베이스에 적합한 트랜젝션 모델을 정의하고 시스템내의 연산들의 병행 수행을 위한 Correctness Criteria에 관해 기술한다. 본 모델은 Lynch의 다중 레벨 Atomicity의 개념을 기초로 협동운영 트렌젝션의 처리에 적합하도록 설계되었다.

릴랙세이션 학습기법과 홉필드 모델에의 적용

오희국(Heekuck Oh) 한국정보과학회 1995 정보과학회논문지 Vol.22 No.7

본 논문은 릴랙세이션 기법이라 불리는 반복 학습 기법과 홉필드 모델에의 적용을 기술한다. 릴랙세이션 기법은 오차 수정 알고리즘으로 원하는 응답과 주어진 입력에 대한 실제 응답을 비교하여 전체 시스템의 성능을 향상시키는 방향으로 신경회로망내의 파라미터를 반복적으로 수정해 가는 기법이다. 이 기법은 기존의 많은 다른 학습 기법과는 달리 몇 가지 흥미로운 특징을 갖고 있다. 첫째로 이 기법은 선형 부등식의 해를 직접 구하는 결정론적 알고리즘에 속한다. 둘째, 함수 극소의 개념이 포함되어 있지 않다. 셋째, 학습율의 선택에 있어 능동적으로 변환하는 조정 기법을 사용하는데, 이는 결과적으로 신속하고 보장된 수렴에 기여하는 특징을 갖고 있다. 릴랙세이션 기법의 응용 예로 홉필드 모델의 작고 제한된 저장 용량을 해결하기 위한 반복 학습 기술을 개발하는데 이 기법을 적용하였다. 그 결과 홉필드 모델의 릴랙세이션 학습 기법은 모든 훈련된 패턴의 되부름을 보장하고 상호 관계가 있는 패턴을 특별한 코딩 기술 없이도 잘 처리하였다. 그 밖에 알고리즘의 학습 속도는 광범위한 학습 매개 변수의 값에 대해 일정하게 높은 수준을 유지하였으며 그들의 선택은 성능에 별다른 영향을 미치지 않았다. This paper presents an iterative learning technique, called the relaxation method, and its application to the Hopfield model. The relaxation method is an error-correction algorithm that iteratively adapts neural network parameters by comparing the response to a given input with the desired response to improve performance. Unlike many existing iterative learning algorithms, the relaxation method has several interesting properties. First, it is a deterministic algorithm that directly solves a system of linear inequalities. Second, no concept of function minimization is introduced. Third, it utilizes a dynamically varying adjustment technique for selecting the learning rate, which, in turn, contributes to fast and guaranteed convergence. The relaxation method is applied to the Hopfield model by developing an iterative learning technique that solves the problem of small and restrictive storage capacity. The relaxation learning algorithm for the Hopfield model provides guaranteed recall of all training patterns and handles correlated patterns without special encoding. In addition, the learning speed of the new technique remains uniformly high over a broad range of learning parameter values and their selection is not an issue.

병행제어 프로토콜에 활용되는 의미정보의 분류

김상진,오희국 漢陽大學校 工學技術硏究所 1999 工學技術論文集 Vol.8 No.1

본 논문에서는 현재까지 제시된 병행제어 기법에 활용되는 의미정보들을 분석하였으며, 의미 정보들이 가지고 있는 특징을 이용하여 분류하였다. 분석한 의미정보로는 의존성, 교환성, 회복성이 있으며, 각 의미정보에 대한 형식화된 정의와 각 정의에 대한 해석을 제공하며, 회복성의 경우에는 연산의 읽기 집합과 쓰기 집합을 이용하여 직렬성을 보장한다는 것을 증명하였다. 그리고 객체로부터 의미정보를 체계적으로 추출할 수 있는 방법론을 분석하고 그것의 문제점을 제시하였다. In this paper, analysis on semantic information used in concurrency control protocol is given. Semantic information covered in this paper are dependancy, commutativity, and recoverability. For each semantic information, formalized definition and the meaning of the information with some examples is given. For recoverability, proof of its serializability is given using read and write set of an operation. We have also analyzed the methodology of retrieving semantic information from an object.

Cooperation-Aware VANET Clouds: Providing Secure Cloud Services to Vehicular Ad Hoc Networks

Hussain, Rasheed,Oh, Heekuck Korea Information Processing Society 2014 Journal of information processing systems Vol.10 No.1

Over the last couple of years, traditional VANET (Vehicular Ad Hoc NETwork) evolved into VANET-based clouds. From the VANET standpoint, applications became richer by virtue of the boom in automotive telematics and infotainment technologies. Nevertheless, the research community and industries are concerned about the under-utilization of rich computation, communication, and storage resources in middle and high-end vehicles. This phenomenon became the driving force for the birth of VANET-based clouds. In this paper, we envision a novel application layer of VANET-based clouds based on the cooperation of the moving cars on the road, called CaaS (Cooperation as a Service). CaaS is divided into TIaaS (Traffic Information as a Service), WaaS (Warning as a Service), and IfaaS (Infotainment as a Service). Note, however, that this work focuses only on TIaaS and WaaS. TIaaS provides vehicular nodes, more precisely subscribers, with the fine-grained traffic information constructed by CDM (Cloud Decision Module) as a result of the cooperation of the vehicles on the roads in the form of mobility vectors. On the other hand, WaaS provides subscribers with potential warning messages in case of hazard situations on the road. Communication between the cloud infrastructure and the vehicles is done through GTs (Gateway Terminals), whereas GTs are physically realized through RSUs (Road-Side Units) and vehicles with 4G Internet access. These GTs forward the coarse-grained cooperation from vehicles to cloud and fine-grained traffic information and warnings from cloud to vehicles (subscribers) in a secure, privacy-aware fashion. In our proposed scheme, privacy is conditionally preserved wherein the location and the identity of the cooperators are preserved by leveraging the modified location-based encryption and, in case of any dispute, the node is subject to revocation. To the best of our knowledge, our proposed scheme is the first effort to offshore the extended traffic view construction function and warning messages dissemination function to the cloud.

AN AUTHENTICATION MECHANISM PREVENTING MALICIOUS DEVICES FROM PARTICIPATING IN ZIGBEE NETWORK

Jaehong Ham,Heekuck Oh 한국멀티미디어학회 2007 한국멀티미디어학회 국제학술대회 Vol.2007 No.-

ZigBee, LR-WPAN's major technology. is based on IEEE 802.15.4 specification and ZigBee Alliance to realize home network environment. While basic security services are provided, there is a lack of more advanced techniques which are indispensable in modern ZigBee application. But, in ZigBee network. ZigBee coordinator progresses key exchange protocol without device authentication when initial device joined in ZigBee network. It can cause various kinds of attacks through malicious devices within ZigBee network. In this paper, we propose an authentication mechanism preventing malicious devices from participating in ZigBee network. The proposed mechanism provides authentication for initial device with ZigBee coordinator which 'serves as authentication server.

On Secure and Privacy-Aware Sybil Attack Detection in Vehicular Communications

Hussain, Rasheed,Oh, Heekuck Springer-Verlag 2014 WIRELESS PERSONAL COMMUNICATIONS Vol.77 No.4

A Step towards User Privacy while Using Location-Based Services

Abbas, Fizza,Oh, Heekuck Korea Information Processing Society 2014 Journal of information processing systems Vol.10 No.4

Nowadays mobile users are using a popular service called Location-Based Services (LBS). LBS is very helpful for a mobile user in finding various Point of Interests (POIs) in their vicinity. To get these services, users must provide their personal information, such as user identity or current location, which severely risks the location privacy of the user. Many researchers are developing schemes that enable a user to use these LBS services anonymously, but these approaches have some limitations (i.e., either the privacy prevention mechanism is weak or the cost of the solution is too much). As such, we are presenting a robust scheme for mobile users that allows them to use LBS anonymously. Our scheme involves a client side application that interacts with an untrusted LBS server to find the nearest POI for a service required by a user. The scheme is not only efficient in its approach, but is also very practical with respect to the computations that are done on a client's resource constrained device. With our scheme, not only can a client anonymously use LBS without any use of a trusted third party, but also a server's database is completely secure from the client. We performed experiments by developing and testing an Android-based client side smartphone application to support our argument.

A Step towards User Privacy while Using Location-Based Services

( Fizza Abbas ),( Heekuck Oh ) 한국정보처리학회 2014 Journal of information processing systems Vol.10 No.4

Nowadays mobile users are using a popular service called Location-Based Services (LBS). LBS is very helpful for a mobile user in finding various Point of Interests (POIs) in their vicinity. To get these services, users must provide their personal information, such as user identity or current location, which severely risks the location privacy of the user. Many researchers are developing schemes that enable a user to use these LBS services anonymously, but these approaches have some limitations (i.e., either the privacy prevention mechanism is weak or the cost of the solution is too much). As such, we are presenting a robust scheme for mobile users that allows them to use LBS anonymously. Our scheme involves a client side application that interacts with an untrusted LBS server to find the nearest POI for a service required by a user. The scheme is not only efficient in its approach, but is also very practical with respect to the computations that are done on a client’s resource constrained device. With our scheme, not only can a client anonymously use LBS without any use of a trusted third party, but also a server’s database is completely secure from the client. We performed experiments by developing and testing an Android-based client side smartphone application to support our argument.

INTRUSION DETECTION SYSTEM FOR HOME SECURITY

Kibaek Kim,Heekuck Oh 한국멀티미디어학회 2007 한국멀티미디어학회 국제학술대회 Vol.2007 No.-

To implement home network system, it is needed a variety of technologies such as wired or wireless network, middleware, and home gateway. Security issue needs to be considered in such a variety of home network systems to maintain and manage effectively. Unlike existing environment, there are many security vulnerabilities and attacks in home networks. However, it is not relevant to prevent the attack to home network using existing solutions. For this reason, we have to develop suitable and effective intrusion detection system to prevent the attack to home network. In this paper, we divided intrusion into two types, which categorized home gateway and domestic network, in order to propose the solution.

Yang과 Chang의 기법의 수학적 결함과 그 해결책

임원우 ( Wonwoo Rhim ),오희국 ( Heekuck Oh ) 한국정보처리학회 2010 한국정보처리학회 학술대회논문집 Vol.17 No.2

2009년 Yang과 Chang은 Computers and Security에 “An ID-based-remote mutual authentication with key agreement scheme on elliptic curve cryptosystem"을 제안하였다. 하지만 제안된 방법에서 사용한 타원곡선 곱셈에서 수학적 오류를 범하였고, 수학적 오류를 수정한 방법을 제안하고자 한다.