• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.1823-1826
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• 2003

본 논문은 디지털 컨텐츠의 지적 재산권 보호를 위해 활발히 연구가 진행되고 있는 디지털 워터마킹 기술의 응용분야로서 CAD 프로그램 상에서 도안된 건축설계도면에 워터마크를 은닉하는 기법을 제안한다. 워터마크 은닉에 필요한 컴퓨터로 설계된 건축도면 정보의 추출과 CAD데이터의 특성에 맞는 워터마크 은닉알고리즘에 대해 연구하여 워터마크를 은닉하고 추출하는 실험을 하였다. 실험결과 은닉된 워터마크는 비가시성을 만족하였으며, format 변환, cropping등에도 워터마크는 추출됨을 확인하였다.

• Proceedings of the KAIS Fall Conference
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• 2006.11a
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• pp.212-215
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• 2006

본 논문에서는 MANET 환경에서 악의적인 노드들로부터 데이터를 보호하고 안전하게 전달하는 방법으로 클러스터 기반의 라우팅 알고리즘인 CBRP를 이용하여 클러스터 헤더간의 데이터 교환처럼 데이터를 캡슐화 하여 데이터의 은닉효과를 주었다. 또한 Diffie-Hellman 키 교환 알고리즘을 이용하여 노드간에 전송되는 데이터를 암호화함으로써 악의적인 노드는 데이터를 습득하더라도 키를 가지고 있지 않기 때문에 어떤 내용인지 알기 어려운 특성을 지니고 있다.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2002.11a
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• pp.514-519
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• 2002

우리는 유머문서의 추천을 위해서 문서 정보, 사용자 정보, 공통 등급매김 정보 등을 모두 이용하는 4 개의 관찰 변수와 이들간 관계의 학습을 위한 은닉변수를 사용한 확률모델을 구축하였다. 이 모델은 학습된 은닉 변수와 가시 변수 간의 관계를 통해 누락 관찰 데이터에 대해서도 추정값을 유도해 낼 수 있으므로 등급매김 정보가 부족하거나 새로운 사용자와 문서의 도입시에 안정적인 추천 성능을 보여 줄 수가 있다. 또한 확률 모델의 학습을 위해서 EMl 알고리즘을 이용하였는데 저평가된 데이터의 이용도를 높이기 위해서 추천을 반대하는 확률 모델을 따로 두고 이들간에 분류모델(classification model)을 두어서 추정값을 분류해내는 방식을 취한다.

• The KIPS Transactions:PartB
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• v.10B no.2
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• pp.143-150
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• 2003

Error concealment plays an important role in combating transmission errors. Methods of error concealment which produce better quality are generally of higher complexity, thus making some of the more sophisticated algorithms is not suitable for real-time applications. In this paper, we develop temporal and spatial error resilient video encoding and data hiding approach to facilitate the error concealment at the decoder. Block interleaving scheme is introduced to isolate erroneous blocks caused by packet losses for spatial area of error resilience. For temporal area of error resilience, data hiding is applied to the transmission of parity bits to protect motion vectors. To do error concealment quickly, a set of edge features extracted from a block is embedded imperceptibly using data hiding into the host media and transmitted to decoder. If some part of the media data is damaged during transmission, the embedded features are used for concealment of lost data at decoder. This method decreases a complexity of error concealment by reducing the estimation process of lost data from neighbor blocks. The proposed data hiding method of parity bits and block features is not influence much to the complexity of standard encoder. Experimental results show that proposed method conceals properly and effectively burst errors occurred on transmission channel like Internet.

• Journal of Internet Computing and Services
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• v.12 no.2
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• pp.9-17
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• 2011

This paper proposes an algorithm that predicts the state of user's next actions, exploiting the HMM (Hidden Markov Model) on user profile data stored in the ubiquitous home network. The HMM, recognizes patterns of sequential data, adequately represents the temporal property implicated in the data, and is a typical model that can infer information from the sequential data. The proposed algorithm uses the number of the user's action performed, the location and duration of the actions saved by "Activity Recognition System" as training data. An objective formulation for the user's interest in his action is proposed by giving weight on his action, and change on the state of his next action is predicted by obtaining the change on the weight according to the flow of time using the HMM. The proposed algorithm, helps constructing realistic ubiquitous home networks.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1347-1359
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• 2017

SQLite database is a file-based DBMS(Database Management System) that provides transactions, and it is loaded on smartphone because it is appropriate for lightweight platform. AS the usage of smartphone increased, SQLite-related crimes can occur. In this paper, we proposed a new concealing method for SQLite db file and a detection method against it. As a result of concealing experiments, it is possible to intentionally conceal 70bytes in the DB file header and conceal original data by inserting artificial pages. But it can be detected by parsing 70bytes based on SQLite structure or using the number of record and index. After that, we proposed detection algorithm for concealed data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.1063-1075
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• 2000

This paper proposes an adaptive error concealment technique for compressed video. Since redundancy is extracted out during compression process, compressed video is vulnerable to errors which occur during transmission of video over error prone networks such as wireless channels and Internet. Error concealment is a process of reconstructing video out of damaged video bit stream. We proved that scalable encoding is very useful for error concealment. Analysis of experiments shows that some part of image is better concealed by using base layer information and other part of image is better concealed by using previous frame information. We developed a technique which enables to decide which methodology is more effective, adaptively, based on motion vectors and regional spatial activity. We used H.263v2 for scalable encoding, but, our approach could be applied to all DCT based video codec.

• Journal of Digital Contents Society
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• v.17 no.6
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• pp.461-469
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• 2016

A novel steganography based on ternary BCH code with t = 2 is presented in this paper. Proposed method utilizes powerful BCH code with t = 2 for data hiding to the DCT coefficients from JPEG images. The presented data hiding technique uses a proposed look up table approach for searching multiple solutions for ternary BCH code with t = 2. The proposed look up table approach enables fast and efficient search for locations of DCT coefficients, which are necessary to modify for hiding data. Presented data hiding technique is the first steganography technique based on ternary BCH code. Experimental results clearly indicate advantages of using ternary BCH compared to binary BCH.

• The Journal of the Korea Contents Association
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• v.8 no.5
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• pp.44-51
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• 2008

Pattern matching and pattern searching in time series data have been active issues in a number of disciplines. This paper suggests a novel pattern matching technology which can be used in the field of stock market analysis as well as in forecasting stock market trend. First, we define conceptual patterns, and extract data forming each pattern from given time series, and then generate learning model using Hidden Markov Model. The results show that the context-based pattern matching makes the matching more accountable and the method would be effectively used in real world applications. This is because the pattern for new data sequence carries not only the matching itself but also a given context in which the data implies.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.11-16
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• 2014

Block truncation coding (BTC) is a recent technique used for compression of monochrome image data. The original algorithm of BTC implement to use the standard mean and the standard deviation. For data hiding, it is needed to modify bit-planes of an images. These modifications yields unacceptable quality of BTC images. Thus, we propose IODBTC (Improved Ordered dithering BTC) improving BTC. In this paper, we improve this problem. Experimental results show that the reconstructed secret messages are the same as the original secret messages, and that the proposed scheme exhibits a good BTC images compared to that of previous schemes.