• Journal of KIISE:Computing Practices and Letters
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• v.7 no.6
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• pp.582-592
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• 2001

Video indexing plays an important role in the applications such as digital video libraries or web VOD which archive large volume of digital videos. Video indexing is usually based on video segmentation. In this paper, we propose a software tool called V2Web Studio which can generate video clips utilizing shot boundary detection algorithm. With the V2Web Studio, the process of clip generation consists of the following four steps: 1) Automatic detection of shot boundaries by parsing the video, 2) Elimination of errors by manually verifying the results of the detection, 3) Building a modeling structure of logical hierarchy using the verified shots, and 4) Generating multiple video clips corresponding to each logically modeled segment. The aforementioned steps are performed by shot detector, shot verifier, video modeler and clip generator in the V2Web Studio respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5572-5595
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• 2016

Multi-server authentication enables the subscribers to enjoy an assortment of services from various service providers based on a single registration from any registration centre. Previously, a subscriber had to register from each service provider individually to avail respective services relying on single server authentication. In the past, a number of multi-server authentication techniques can be witnessed that employed lightweight and even computationally intensive cryptographic operations. In line with this, Zhu has presented a chaotic map based multi-server authentication scheme recently, which is not only vulnerable to denial-of-service attack, stolen-verifier attack, but also lacks anonymity. This research aims at improving the Zhu's protocol in terms of cost and efficiency. Moreover, the comparative study is presented for the performance of improved model against the existing scheme, and the security of proposed model is formally proved using BAN Logic.

• Journal of Information Processing Systems
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• v.8 no.4
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• pp.653-668
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• 2012

In this study, an improved HMM based recognition model is proposed for online English and Korean handwritten characters. The pattern elements of the handwriting model are sub character strokes and ligatures. To deal with the problem of handwriting style variations, a modified Hierarchical Clustering approach is introduced to partition different writing styles into several classes. For each of the English letters and each primitive grapheme in Korean characters, one HMM that models the temporal and spatial variability of the handwriting is constructed based on each class. Then the HMMs of Korean graphemes are concatenated to form the Korean character models. The recognition of handwritten characters is implemented by a modified level building algorithm, which incorporates the Korean character combination rules within the efficient network search procedure. Due to the limitation of the HMM based method, a post-processing procedure that takes the global and structural features into account is proposed. Experiments showed that the proposed recognition system achieved a high writer independent recognition rate on unconstrained samples of both English and Korean characters. The comparison with other schemes of HMM-based recognition was also performed to evaluate the system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.870-879
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• 1997

At crypto'89 meeting, D. chaum suggested an undeniable signature scheme. Undeniable signatures are verified via a protocol between the signer and verifier, so the cooperation of the signer is necessary. So far, ther have been several variants of undeniable signatures to obtain a signature scheme, which can control the abous of ordinary digital signatures. In this paper we integrate these variants into a generalized undeniable-type signature scheme. Also, it will be pointed out, that undeniable signature schemes but its first realization are vulnerable in full view of eavesdropping third party. Moreover, to solve this problem, we propose a new type of digital signature, called "result-indisting-uishable undeniable signature" and construct a practical protocol that implements it.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.393-398
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• 2003

본 논문에서는 사용자 인증에 사용되는 패스워드 검증자의 안전성을 더욱 보강한 새로운 패스워드 검증자 기반 키 분배 프로토콜을 제안한다 기존 패스워드 기반 키 분배프로토콜 방식은 네트워크 상에서 패스워드의 안전한 전송이 어려웠고, 패스워드 파일의 안전한 보호가 어렵다는 문제가 있었다. 이에 패스워드 파일을 그대로 서버에 저장하지 않고 패스워드를 사용하여 생성한 검증자(verifier)를 저장하게 함으로써 패스워드파일을 보다 안전하게 보호할 수 있게 되었으며, 서버가 사용자의 패스워드를 알지 못하더라도 검증자를 사용한 증명방식을 통해 사용자를 인증할 수 있게 되었다. 본 논문에서는 사용자와 서버의 비밀정보로 만든 새로운 형태의 검증자를 사용하고, 사용자는 다른 저장정보 없이 기억하고 있는 ID와 패스워드만을 사용하여 키 분배를 수행하는 패스워드 검증자 기반 키 분배 프로토콜을 제안한다. 제안하는 프로토콜의 안전성 분석을 위해 active impersonation과 forward secrecy, man-in-the-middle attack, off-line dictionary attack 등의 공격 모델을 적용하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1027-1030
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• 2015

하드웨어 디자인 설계에서 초기 단계의 설계 오류 발견은 개발 비용 감소 및 설계 시간 단축 측면에서 그 효과가 매우 크다. 이러한 초기 설계 오류 발견을 위한 대표적인 방법으로는 정형 검증(formal verification)이 있으며, Cadence SMV(Symbolic Model Verifier)는 정형 검증을 위해 Verilog HDL(Hardware Description Language)을 SMV로 자동 변환 해주는 장점이 있지만, 사건 기반 구조(event based structures)의 sensitivity list에 대한 지원을 하지 않는 한계가 있다. 이에 본 논문에서는 Cadence SMV에서 디지털회로(digital circuit) 중 하나인 조합 논리회로(combinational logic circuit)를 sensitivity list가 고려된 검증이 가능하도록 하는 방법을 제안한다. 신뢰성 있는 실험을 위해 본 논문에서는 제안하는 방법의 일반적인 규칙을 도출하였고, 도출된 규칙이 적용된 SMV 파일을 생성하는 자동화 프로그램을 구현하여 실험하였다. 실험결과 제안한 방법을 적용한 경우 기존 Cadence SMV가 발견하지 못한 설계상의 오류를 발견할 수 있었다.

• Journal of the Korea Convergence Society
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• v.10 no.11
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• pp.41-46
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• 2019

Recently, the Byzantine Fault Tolerance(BFT) family of consensus algorithms has been attracting attention as the problems of the Proof-of-work (PoW) blockchain consensus algorithms result in energy waste and lack of scalability. One of the great features of the PBFT family consensus algorithms is the formation of a set of validators and consensus within them. In this paper, we compared and analyzed the scalability, targeted attackability, and civil attackability of Algorand, Stellar, and EOS validator set formation methods among BFT family consensus algorithms. Also, we found the problems of each verifier formation method through data analysis, and the consensus algorithms showed that the centralization phenomenon that the few powerful nodes dominate the whole system in common.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.1003-1019
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• 2019

Threshold ring signature scheme enables any t entities from N ring members to spontaneously generate a publicly verifiable t-out-of-N signature anonymously. The verifier is convinced that the signature is indeed generated by at least t users from the claimed group, but he cannot tell them apart. Threshold ring signatures are significant for ad-hoc groups such as mobile ad-hoc networks. Based on the lattice-based ring signature proposed by Melchor et al. at AFRICRYPT'13, this work presents a lattice-based threshold ring signature scheme, employing the technique of message block sharing proposed by Choi and Kim. Besides, in order to avoid the system parameter setup problems, we proposed a message processing technique called "pad-then-permute", to pre-process the message before blocking the message, thus making the threshold ring signature scheme more flexible. Our threshold ring signature scheme has several advantages: inherits the quantum immunity from the lattice structure; has considerably short signature and almost no signature size increase with the threshold value; provable to be correct, efficient, indistinguishable source hiding, and unforgeable.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.280-283
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• 2013

최근 원자력 발전소, 의료 시스템, 항공 시스템 등과 같이 사람의 생명과 밀접하게 관련되어 있는 소프트웨어로 제어하는 시스템들이 점차 늘어나고 있다. 차량에서 또한 차량 제어 소프트웨어의 오작동으로 인한 잦은 사고로 인하여 운전자와 탑승자의 생명을 위협 받고 있다. 이러한 문제로 인하여 차량시스템 제어 소프트웨어도 안전성 확보를 위한 기술로 차량에 통신 기술을 접목한 차량 통신 기술에 대한 관심이 높아지고 있다. 차량 운전자 뿐 아니라 탑승자의 안전과 밀접하기 때문에 많은 연구가 진행되고 있다. 이러한 많은 연구 중 긴급메시지전송 시스템은 차량 간 통신(V2V)을 통한 운전자의 안전성 확보에 대한 연구다. 본 논문에서는 차량 긴급메시지 전송에 필요한 모듈을 구조적으로 나누고 이를 통하여 긴급메시지 전송시스템 구조의 안전성을 평가한다. 긴급메시지 전송시스템의 안정성을 검증하기 위하여 오토마타 모델링을 통한 시스템 구조를 설계하고 검증을 위해 CTL 논리식 정의, SMV(Symbolic Model Verifier)검증도구를 통한 시스템 안전성 모델 검사를 하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.6
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• pp.15-24
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• 2004

Electronic commerce is widely used with the development of information communication technologies in internet using public key certificates. And the study for access control in Web application and DB system is also progressed actively. There are many verification method for PKC(Public Key Certificates), which are CRL, OCSP, SCVP and others. But their certificates verification methods for PKC cannot to be applied to PMI(Privilege Management Infrastructure) which is using AC(Attribute certificates) because of synchronization of PKC and AC. It is because AC has no public key, AC Verifier must get the PKC and verify the validity on PKC and AC. So in this paper we proposed the new AC-based certificate verification model. which provide the synchronization in two certificates(AC and PKC).