• Proceedings of the Korea Multimedia Society Conference
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• 1998.04a
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• pp.205-209
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• 1998

시각암호는 n개로 분산된 비밀화상을 슬라이드와 같이 물리적으로 중첩 가능한 곳에 인쇄하여 그룹내 n명에게 슬라이드를 배포한 후, 임의의 k명 이상의 슬라이드를 겹치면 비밀 화상을 복원할 수 있지만, k-1명 이하의 슬라이드를 겹치는 경우에는 비밀화상을 복원할 수 없는 방식이다. 이 논문에서는 (k, n) 시각암호의 휘도(contrast)를 개선하기 위한 구성법에서 모든 경우에 동일 휘도를 유지하면서 부화소의 수를 줄이기 위한 새로운 구성법을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.365-367
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• 2003

핑거프린팅 기법은 암호학적인 기법들을 이용하여 디지털 데이터를 불법적으로 재배포한 사용자를 찾아냄으로써 디지털 데이터의 저작권을 보호한다. 익명성이 보장되는 핑거프린팅 기법은 대칭적인 기법과 달리 사용자만이 핑거프린트가 삽입된 데이터를 알 수 있고 비대칭 기법과 달리 데이터가 재배포되기 전에는 사용자의 익명성이 보장되는 기법이다. 본 논문에서는 사용자의 익명성이 보장되는 새로운 핑거프린팅 기법을 제안한다. 비밀분산법을 이용하여 사용자의 신원정보를 숨겨두었다가 재배포 발견시 조정자에게 누가 재배포하였는지 증거를 제출함으로써 재배포자의 배포 사실을 증명한다. 또한 등록시에 Schnorr 서명을 이용하여 고발된 사용자가 범행을 부인할 수 없도록 한다. 제안된 방법은 이산대수문제와 양자간 안전한 계산과정의 안전성에 근거하여 사용자의 익명성이 보장된다.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.5_6
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• pp.353-359
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• 2004

The illegal copying and redistribution of digitally-stored information is a crucial problem to distributors who electronically sell digital data. Fingerprinting scheme is a techniques which supports copyright protection to track redistributors of electronic information using cryptographic techniques. Anonymous fingerprinting schemes, differ from symmetric fingerprinting, prevent the merchant from framing a buyer by making the fingerprinted version known to the buyer only. And the scheme, differ from asymmetric fingerprinting, allows the buyer to purchase goods without revealing her identity to the merchant. In this paper, a new anonymous fingerprinting scheme based on secret sharing is introduced. The merchant finds a sold version that has been distributed, and then he is able to retrieve a buyer's identity and take her to court. And Schnorr's digital signature prevents the buyer from denying the fact he redistributed. The buyer's anonymity relies on the security of discrete logarithm and secure two-party computations.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1996.11a
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• pp.261-271
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• 1996

M.Naor와 A.Shamir의 시각암호는 기존의 비밀 분산법에서 분산/복호시 연산량이 많은 것과는 달리 인간의 시각에 의해서 직접 복호될 수 있는 방식이다. 본 논문에서는 시각암호의 화장 방식인 복수 화상을 숨기는 방식에서 숨기려는 비밀화상의 수가 증가함에 따라 share 크기가 기하 급수적으로 커지는 문제점을 해결하기 위하여 고정 가중치부호의 해밍 거리를 조정하여 share 크기를 줄이는 방법을 제안한다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1996.11a
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• pp.251-260
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• 1996

Naor & Shamir는 시각 암호에 관한 기본 개념을 제시하고 이를 위한 구성법을 제안하고 있다. 이는 복잡한 암호학적인 계산 없이 숨겨진 비밀을 복호하는 새로운 암호형태로서 대단히 안전하고 구현이 용이하다는 장점을 가지고 있다. 본 논문에서는 (2, n)시각 비밀 분산법의 여러 방법들에 대하여 고찰한다 또한, 시각 암호의 실질적인 응용의 효과를 기대할 수 있는 농담화상에 적용하기 위한 시각 암호의 구성법과실제 구현결과를 보인다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1992.06a
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• pp.41-45
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• 1992

• Communications of Mathematical Education
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• v.22 no.4
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• pp.515-531
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• 2008

The visual cryptography scheme is a simple method which can be decoded directly the secret information in human visual system without performing any cryptographic computations. For some secret of image type, we scatter them to random n images and if any threshold (or more) of them are stacked together then original image is visible. In this paper we consider (2,n) visual cryptography scheme and show a construction method of the sample matrix using the rule of binomial coefficients $_nC_2$. This scheme can contribute interesting and effectiveness to the study of mathematics.

• The Transactions of the Korea Information Processing Society
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• v.13 no.2
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• pp.34-40
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• 2024

Secret sharing is a cryptographic technique that involves dividing a secret or a piece of sensitive information into multiple shares or parts, which can significantly increase the confidentiality of a secret. There has been a lot of research on secret sharing for different contexts or situations. Tassa's conjunctive secret sharing method employs polynomial derivatives to facilitate hierarchical secret sharing. However, the use of derivatives introduces several limitations in hierarchical secret sharing. Firstly, only a single group of participants can be created at each level due to the shares being generated from a sole derivative. Secondly, the method can only reconstruct a secret through conjunction, thereby restricting the specification of arbitrary secret reconstruction conditions. Thirdly, Birkhoff interpolation is required, adding complexity compared to the more accessible Lagrange interpolation used in polynomial-based secret sharing. This paper introduces the multi-compartment secret sharing method as a generalization of the conjunctive hierarchical secret sharing. Our proposed method first encrypts a secret using external groups' shares and then generates internal shares for each group by embedding the encrypted secret value in a polynomial. While the polynomial can be reconstructed with the internal shares, the polynomial just provides the encrypted secret, requiring external shares for decryption. This approach enables the creation of multiple participant groups at a single level. It supports the implementation of arbitrary secret reconstruction conditions, as well as conjunction. Furthermore, the use of polynomials allows the application of Lagrange interpolation.

• The KIPS Transactions:PartC
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• v.17C no.5
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• pp.399-406
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• 2010

Many problems are arisen due to the weakness in the security and invasion to privacy by malicious attacker or internal users while various data services are available in ubiquitous network environment. The matter of controlling security for various contents and large capacity of data has appeared as an important issue to solve this problem. The allocation methods of Ito, Saito and Nishizeki based on traditional polynomial require all shares to restore the secret information shared. On the contrary, the secret information can be restored if the shares beyond the threshold value is collected. In addition, it has the effect of distributed DBMS operation which distributes and restores the data, especially the flexibility in realization by using parameters t,v,k in combinatorial design which has regularity in DB server and share selection. This paper discuss the construction of new share allocation method and data distribution/storage management with the application of matrix structure of t-(v,k,1) design for allocating share when using secret sharing in management scheme to solve the matter of allocating share.

• Journal of the Korea Society for Simulation
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• v.17 no.3
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• pp.95-105
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• 2008

In this paper, we propose the DAMMC(Distributed Authentication Model using Multi-level Cluster) for wireless sensor networks. The proposed model is that one cluster header in m-layer has a role of CA(Certificate Authority) but it just authenticates sensor nodes in lower layer for providing an efficient authentication without authenticating overhead among clusters. In here, the m-layer for authentication can be properly predefined by user in consideration of various network environments. And also, the DAMMC uses certificates based on the threshold cryptography scheme for more reliable configuration of WSN. Experimental results show that the cost of generation and reconfiguration certification are decreased but the security performance are increased compared to the existing method.