• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.75-87
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• 2001

The Conditional Access System is the complete system for ensuring that broadcasting services are only accessible to those who are entitled to receive them. Four major parts to this system are scrambling, descrambling, authentication and encryption. For the proper operation, which means hard-to- break and uninterrupted service, secure key management and efficient delivery mechanism are very important design factors to this system. Performance analysis is another important factor to this system that is used in massive subscriber environment. In this thesis, one of the secure and efficient key management mechanisms is proposed. For the secrecy of this mechanism, hierarchical stacking of keys and key generation matrix are proposed. For the proof of efficient delivery of those keys, simulation results and performance analysis. which is based on queuing analysis, are presented. Lastly, optimal key generation and delivery period, maximal and minimal key deliver time, and communication capacity for data collection are presented for various subscriber volume.

• Journal of KIISE
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• v.44 no.7
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• pp.703-709
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• 2017

Outsourcing databases is to offload storage and computationally intensive tasks to the third party server. Therefore, data owners can manage big data, and handle queries from clients, without building a costly infrastructure. However, because of the insecurity of network systems, the third-party server may be untrusted, thus the query results from the server may be tampered with. This problem has motivated significant research efforts on authenticating various queries such as range query, kNN query, function query, etc. Although aggregation queries play a key role in analyzing big data, authenticating aggregation queries has not been extensively studied, and the previous works are not efficient for data with high dimension or a large number of distinct values. In this paper, we propose the AMR-tree that is a data structure, applied to authenticate aggregation queries. We also propose an efficient proof construction method and a verification method with the AMR-tree. Furthermore, we validate the performance of the proposed algorithm by conducting various experiments through changing parameters such as the number of distinct values, the number of records, and the dimension of data.

• Journal of the Korea Computer Industry Society
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• v.2 no.8
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• pp.1089-1098
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• 2001

Structure information contained in a structured document supports various access paths to document. In order to use structure information contained in a structured document, it is required to construct an index structural on document structures. Content indexing and structure indexing per document require high memory overhead. Therefore, processing of pure structure queries based on document structure like relationship between elements or element orders, low memory overhead for indexing are required. This paper suggests the GDIT(Global Document Instance Tree) data structure and indexing scheme about structure of document which supports low memory overhead for indexing and powerful types of user queries. The structure indexing scheme only index the lowest level element of document and does not effect number of document having retrieval element. Based on the index structure, we propose an query processing algorithm about pure structure, proof the indexing schemes keeps up indexing efficient in terms of space. The proposed index structure bases GDR concept and uses index technique based on GDIT.

• Journal of Korean Library and Information Science Society
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• v.4
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• pp.91-111
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• 1977

The view point of the library is treated as a first subject. This study is scheduled to construct, as a experimental study, the system of the Library Science. The study of this fields is called upon greatly because the trial to understand library as a socio-cultural phenomenon did not study as many times. As a result of the study, library is defined as ${\ulcorner}Structural Formation of Inquirying Behavior{\lrcorner}$. Not only technique and actual proof are possible in this study but also this definition is technical definition to indicate the main phenomenon of Librarial Behavior. This schedule represent the trial to define Library Behavior which could anticipate and fabricate when we analyze this definition First, we can find out, first of all, the researching behavior among the human behaviors and then human behavior has the condition of practice. At last, researching behavior can not have any result when it is a natural situation, it has only the meaning when it is guided by an obvious intention. The object of the library is just this human behavior. Second, Formation permits the guidance and self-control at the same-times. The answer about what we find out and practice make it possible the act of guidance. This guidance can't burden any subject but permit the people to result his own researching behaviors. He can save his activities, his own researching behaviors by the result of it. Third, The statematical means efficient performances, and them efficient performances is impossible, here is 'discoveries' of behavior itself. The system of the library is the formation of the relation between the accumulated civilizations and accumulated civilizations. As the definitions of the above mentions, library has the big abilities to the creation and succession of the civilization. As the contemporary view-points, there are some questions about the above described definition can meet it of the library. When we frame the science of library as the learning systems, we can't but the library as this definitions.

• Journal of the Korean Society for Library and Information Science
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• v.45 no.4
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• pp.77-102
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• 2011

The purpose of this study is to design, implement and evaluate a personalized search system using gathered information on users to provide more accurate search results. For this purpose, a hybrid-based user profile is constructed by using subject classification. In order to evaluate the performance of the proposed system, experts directly measured and evaluated MRR, MAP and usability by using the Korean journal articles of science and technology DB. Its performance was better than the general search system in the area of "Computer Science" and "Library and Information Science". Especially better results were shown when tested on ambiguous keywords. Evaluation through in-depth interviews proved that the proposed personalized search system was more efficient in looking up and obtaining information. In addition, the proposed personalized search system provided a variety of recommendation systems which proved helpful in navigating for new information. High user satisfaction ratings on the proposed personalized search system were another proof of its usefulness. In this study, we were able to prove through expert evaluation that the proposed personalized search system was more efficient in information retrieval.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.5
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• pp.2427-2445
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• 2016

In contrast to traditional "store-and-forward" routing mechanisms, network coding offers an elegant solution for achieving maximum network throughput. The core idea is that intermediate network nodes linearly combine received data packets so that the destination nodes can decode original files from some authenticated packets. Although network coding has many advantages, especially in wireless sensor network and peer-to-peer network, the encoding mechanism of intermediate nodes also results in some additional security issues. For a powerful adversary who can control arbitrary number of malicious network nodes and can eavesdrop on the entire network, cryptographic signature schemes provide undeniable authentication mechanisms for network nodes. However, with the development of quantum technologies, some existing network coding signature schemes based on some traditional number-theoretic primitives vulnerable to quantum cryptanalysis. In this paper we first present an efficient network coding signature scheme in the standard model using lattice theory, which can be viewed as the most promising tool for designing post-quantum cryptographic protocols. In the security proof, we propose a new method for generating a random lattice and the corresponding trapdoor, which may be used in other cryptographic protocols. Our scheme has many advantages, such as supporting multi-source networks, low computational complexity and low communication overhead.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.6
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• pp.1304-1316
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• 2009

This study is for the pursuit of the basic application of the efficient conversion factor in the fee contract. This aims to investigate the effects of DEA efficiency index and conversion factors to identify and group the 60 hospitals with intern and residents education. To achieve the aims, AHP was used to select the inuput and output variables for DEA. It was found that the more inefficient in the technical and scale side, the higher the conversion factors were. Conversion factor and DEA efficiency index can be used very effectively to group and discriminant hospitals into a specialized general hospital and a general hospital. Even if the variables used to calculate DEA efficiency are applied to discriminant analysis, The conversion factor and DEA efficiency index have a significant power to make a function modeling. So, if we can make a more conclusive proof based on the large number samples, We can imagine to introduce a efficiency concept in the insurance fee contracts about a conversion factor in Korea Health Insurance System.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.4
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• pp.75-88
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• 2007

Current electronic voting systems are not sufficient to satisfy trustworthy elections as they do not provide any proof or confirming evidence of their honesty. This lack of trustworthiness is the main reason why e-voting is not widespread even though e-voting is expected to be more efficient than the current plain paper voting. Many experts believe that the only way to assure voters that their intended votes are casted is to use paper receipts. In this paper, we propose an efficient scheme for issuing receipts to voters in an e-voting environment using the well-known cut-and-choose method. Our scheme does not require any special printers or scanners, nor frequent observations of voting machines. In addition, our scheme is more secure than the previous schemes.

• Journal of applied mathematics & informatics
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• v.30 no.3_4
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• pp.365-380
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• 2012

Non-negative matrix factorization (NMF) is a very efficient method to explain the relationship between functions for finding basis information of multivariate nonnegative data. The multiplicative update (MU) algorithm is a popular approach to solve the NMF problem, but it fails to approach a stationary point and has inner iteration and zero divisor. So the elementwisely alternating projected gradient (eAPG) algorithm was proposed to overcome the defects. In this paper, we use the fact that the equilibrium point is stable to prove the convergence of the eAPG algorithm. By using a classic model, the equilibrium point is obtained and the invariant sets are constructed to guarantee the integrity of the stability. Finally, the convergence conditions of the eAPG algorithm are obtained, which can accelerate the convergence. In addition, the conditions, which satisfy that the non-zero equilibrium point exists and is stable, can cause that the algorithm converges to different values. Both of them are confirmed in the experiments. And we give the mathematical proof that the eAPG algorithm can reach the appointed precision at the least iterations compared to the MU algorithm. Thus, we theoretically illustrate the advantages of the eAPG algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.1
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• pp.119-131
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• 2013

With the explosive growth of computer networks, many remote service providing servers and multi-server network architecture are provided and it is extremely inconvenient for users to remember numerous different identities and passwords. Therefore, it is important to provide a mechanism for a remote user to use single identity and password to access multi-server network architecture without repetitive registration and various multi-server authentication schemes have been proposed in recent years. Recently, Tsaur et al. proposed an efficient and secure smart card based user authentication and key agreement scheme for multi-server environments. They claimed that their scheme satisfies all of the requirements needed for achieving secure password authentication in multi-server environments and gives the formal proof on the execution of the proposed authenticated key agreement scheme. However, we find that Tsaur et al.'s scheme is still vulnerable to impersonation attack and many logged-in users' attack. We propose an extended scheme that not only removes the aforementioned weaknesses on their scheme but also achieves user anonymity for hiding login user's real identity. Compared with other previous related schemes, our proposed scheme keeps the efficiency and security and is more suitable for the practical applications.