• Journal of Communications and Networks
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• 제10권1호
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• pp.10-17
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• 2008

In traditional digital signature schemes, certificates signed by a trusted party are required to ensure the authenticity of the public key. In Asiacrypt 2003, the concept of certificateless signature scheme was introduced. The advantage of certificateless public key cryptography successfully eliminates the necessity of certificates in the traditional public key cryptography and simultaneously solves the inherent key escrow problem suffered in identity-based cryptography. Recently, Yap et al. proposed an efficient certificateless signature scheme and claimed that their scheme is existentially unforgeable in the random oracle model. In this paper, we show that the certificateless signature scheme proposed by Yap et al. is insecure against public key replacement attacks. Furthermore, we propose an improved certificateless signature scheme, which is existentially unforgeable against adaptive chosen message attacks under the computational Diffie-Hellman assumption in the random oracle model and provide the security proof of the proposed scheme.

• 한국경영과학회지
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• 제23권3호
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• pp.109-122
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• 1998

A Process Quality Information System (PQIS) for the CIM environment is presented. The system includes three subsystems which are qualify control, statistical analysis, and information management. As part of CIM, the PQIS was designed by using the ICAM Definition(IDEF) methodology. The Oracle-CDE was utilized as a graphic development tool which made the system more user friendly. PQIS operates on IBM or compatible PCs under MS-Windows and Oracle DBMS. The methodology developed in this research provides a foundation for the application of CIM subsystems.

• Communications for Statistical Applications and Methods
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• 제25권5호
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• pp.453-470
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• 2018

We study how to distinguish the parameters of the sparse autoregressive (AR) process from zero using a non-convex penalized estimation. A class of non-convex penalties are considered that include the smoothly clipped absolute deviation and minimax concave penalties as special examples. We prove that the penalized estimators achieve some standard theoretical properties such as weak and strong oracle properties which have been proved in sparse linear regression framework. The results hold when the maximal order of the AR process increases to infinity and the minimal size of true non-zero parameters decreases toward zero as the sample size increases. Further, we construct a practical method to select tuning parameters using generalized information criterion, of which the minimizer asymptotically recovers the best theoretical non-penalized estimator of the sparse AR process. Simulation studies are given to confirm the theoretical results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1904-1919
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• 2015

Deniable authentication protocol allows a sender to deny his/her involvement after the protocol run and a receiver can identify the true source of a given message. Meanwhile, the receiver has no ability to convince any third party of the fact that the message was sent by the specific sender. However, most of the proposed protocols didn't achieve confidentiality of the transmitted message. But, in some special application scenarios such as e-mail system, electronic voting and Internet negotiations, not only the property of deniable authentication but also message confidentiality are needed. To settle this problem, in this paper, we present a non-interactive identity-based deniable authenticated encryption (IBDAE) scheme using pairings. We give the security model and formal proof of the presented IBDAE scheme in the random oracle model under bilinear Diffie-Hellman (BDH) assumption.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권2호
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• pp.881-896
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• 2016

Certificate-based cryptography is a useful public key cryptographic primitive that combines the merits of traditional public key cryptography and identity-based cryptography. It not only solves the key escrow problem inherent in identity-based cryptography, but also simplifies the cumbersome certificate management problem in traditional public key cryptography. In this paper, by giving a concrete attack, we first show that the certificate-based encryption scheme without bilinear pairings proposed by Yao et al. does not achieve either the chosen-ciphertext security or the weaker chosen-plaintext security. To overcome the security weakness in Yao et al.'s scheme, we propose an enhanced certificate-based encryption scheme that does not use the bilinear pairings. In the random oracle model, we formally prove it to be chosen-ciphertext secure under the computational Diffie-Hellman assumption. The experimental results show that the proposed scheme enjoys obvious advantage in the computation efficiency compared with the previous certificate-based encryption schemes. Without costly pairing operations, it is suitable to be employed on the computation-limited or power-constrained devices.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1972-1988
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• 2013

In order to deal with key exposure problem, we introduce forward secure technique into certificateless proxy signature scheme, and propose the formal definition and security model of the forward secure certificateless proxy signature. Our security model takes into account the super adversary in certificateless signature. Furthermore, we present a construction of forward secure certificateless proxy signature scheme with bilinear maps. Based on the difficulty of computational Diffie-Hellman problem, we prove the scheme is secure against chosen message attack in the random oracle model. Finally, we analyze efficiency of the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5553-5571
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• 2016

In this paper, we introduce a new concept called generalized ring signcryption (GRSC), which can achieve ring signature and ring signcryption functions with only one key pair and one algorithm. It is very useful for a system which has a large number of users, or has limited storage space, or whose function requirements may be changed later. We give a formal definition and a security model of GRSC and propose a concrete scheme based on bilinear pairings. In the random oracle model, the scheme's confidentiality can be proved under the GBDH assumption, and its unforgeability can be proved under GDH' assumption, and what is more, this scheme also allows unconditional anonymity. Compared with other identity-based ring signcryption schemes that use bilinear pairings as well, our scheme is a highly efficient one.

• Spatial Information Research
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• 제5권2호
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• pp.195-198
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• 1997

WEB기반의 환경 GIS자료 관리를 위해 JVM, JDBC, Oracle DB을 이용한다. 본 논문에서의 다루는 환경 GIS자료에는 위성, 주제도, GIS자료 등이 있으며, 이 자료는 공간 정보와 속성 정보를 가지고 DB에 존재한다. 자료의 검색은 WEB Broswer의 조회용 지도를 이용한 공간 검색과 비공간 속성 정보에 의한 검색 기능을 제공한다. 자료 등록은 WEB Broswer에서 자료 등록 시스템을 이용한다.

• 한국컴퓨터정보학회논문지
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• 제23권2호
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• pp.53-61
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• 2018

In this paper, the author proposes an efficient group key agreement scheme in a mobile environment where group members frequently join and leave. This protocol consists of basic protocols and general ones and is expected to be suitable for communications between a mobile device with limited computing capability and a key distributing center (or base station) with sufficient computing capability. Compared with other schemes, the performance of the proposed protocol is a bit more efficient in the aspects of the overall cost for both communication and computation where the computational efficiency of the scheme is achieved by using exclusive or operations and a one-way hash function. Also, in the aspect of security, it guarantees both forward and backward secrecy based on the computational Diffie-Hellman (CDH) assumption so that secure group communication can be made possible. Furthermore, the author proves its security against a passive adversary in the random oracle model.

• 디지털콘텐츠
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• 10호통권29호
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• pp.100-113
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• 1995

데이터베이스라 하면 어렴풋이 어떻다하는 것은 알 것이다. 그러나 데이터베이스를 제작하는 툴 즉 데이터베이스 관리시스템(DBMS)은 직접 접해본 적은 거의 없을 것이다. 접한다 해도 과연 이 프로그램이 DBMS인지 또는 DBMS라 할지라도 어떻게 다루는지 모르고 지나치는 경우가 많을 것이다. 그리고 데이터베이스를 구축하고 프로그램을 선택할 때 DBMS에 대한 자료가 없어서 망설이는 경우도 있을 것이다. 또한 국내에 유통되는 국내외 제작한 많은 DBMS들이 있다. 이 많은 DBMS들 중에서 내가 필요로 하는 것은 어떤 제품인지 판가름하기는 좀 곤란할 것이다. 이러한 독자들의 고민을 조금이나마 해소하기 위해서 본지에서는 매월 1개 제품을 선택하여 소개하고자 한다. 지난호 사이베이스에 이어 두번째로 오라클을 게재하고자 한다. 이번에 게재되는 ORACLE은 지난 9월에 선보인 ORACLEWORKGROUP/20000과 ORACLE 7 데이터베이스 관리시스템 R7.1을 소개하고자 한다.