• Review of KIISC
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• v.5 no.4
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• pp.58-90
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• 1995

PGP(Pretty Good Privacy)는 전자우현에 사용되는 보안도구로써 현재 인터넷(Internet)상에서 광범위하게 사용되고 있다. 전자우편에서 필요로 하는 기밀성, 무결성, 송신자 인증, 송신부인방지등의 기능을 모두 제공해 주고 있고 특히, 사용되는 키에 대한 인증을 하나의 기관에서 전담하지 않고, PGP의 사용자들에 의한 키 인증방식을 채택하고 있는 것이 특징이다. 본고에서는 PGP의 효과적인 보급을 위해 전자우편에 필요한 기본 암호 메카니즘과 PGP의 구조 및 사용방법을 살펴본다.

• Journal of the Korean Society for information Management
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• v.25 no.1
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• pp.75-98
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• 2008

With explosive growth in the area of the Internet and IT services, various types of e-documents are generated and circulated. An e-Document is a sort of electronic records which a organization performs works and goals. In this study, we propose a security algorithm for secure use and distribution of e-documents. Especially, the proposed method can be applied to generate digital signature which can guarantee authenticity, integrity, confidentiality of an e-document and authenticate authorized users. Also, we can get higher security level as using a smart card that provides highly storing capacity and security. We carried out an experiment to verify efficiency and security of the proposed method.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11
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• pp.3576-3583
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• 2000

Digital watermarks have recently been proposed for the purposes of copyright ptotechtion and autheutication for multimedia contents. A watermarking technique consists of an algorithm that incorporates a watermarking structure into an image in the spatial or frequency domains. In this paper we proposed a new watermarking method for authentication and integrity of digital images and the proposed algorithm uses the MD5 hash funiction and a symmetric key encryption algorithm. To decide the position of embedding watermark and the bit pasitionin the original image, the secret key is used as an input of the MD5 hash function. The simulation results show that the proposed algorithm has the advantage of difficulty to find positions of inserted watermarks, and keep the similar watermarked image quabty with Wong's method.

• Journal of KIISE
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• v.43 no.11
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• pp.1245-1258
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• 2016

Cryptographic technologies providing confidentiality and integrity such as encryption algorithms and message authentication codes (MACs) are necessary for preventing security threats in the Internet of Things (IoT) where various kinds of devices are interconnected. As a number of encryption schemes that have passed security verification are not necessarily suitable for low-power and low-performance IoT devices, various lightweight cryptographic schemes have been proposed. However, a study of lightweight MACs is not sufficient in comparison to that of lightweight block ciphers. Therefore, in this paper, we reviewed various kinds of MACs for their classification and analysis and then, we presented a new way for future MAC development. We also implemented major MAC algorithms and performed experiments to investigate their performance degradation on low-end micro-controllers.

• Journal of Digital Convergence
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• v.12 no.4
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• pp.285-291
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• 2014

Recent, development of wireless communication devices are rapidly and these device being deployed to the user very fast. By this results, a wired network device and the new device such as wireless devices incorporate. Then a demand of new mesh network is rapidly growing. In this wired/wireless integrated network environment, the network is configured automatically, and a user or wireless communication devices must be provided for authentication services. But, these services do not in the real world. Therefore, in this paper, we propose that wired/wireless integrated network environment to automatically configure the network using OpenFlow and the authentication system using Kerberos method. Our proposed system to be able to provide authentication services, confidentiality, integrity services for user or wired/wireless communication devices. And it can be prvented as well to man-in-the-middle attacks.

• The KIPS Transactions:PartB
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• v.19B no.2
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• pp.83-92
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• 2012

Multimedia contents can be copied and manipulated without quality degradation. Therefore, they are vulnerable to digital forgery and illegal distribution. In these days, with increasing the importance of multimedia security, various multimedia security techniques are studied. In this paper, we propose a content authentication algorithm based on reversible watermarking which supports JPEG compression commonly used for multimedia contents. After splitting image blocks, a specific authentication code for each block is extracted and embedded into the quantized coefficients on JPEG compression which are preserved against lossy processing. At a decoding process, the watermarked JPEG image is authenticated by extracting the embedded code and restored to have the original image quality. To evaluate the performance of the proposed algorithm, we analyzed image quality and compression ratio on various test images. The average PSNR value and compression ratio of the watermarked JPEG image were 33.13dB and 90.65%, respectively, whose difference with the standard JPEG compression were 2.44dB and 1.63%.

• Journal of Digital Convergence
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• v.19 no.10
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• pp.287-293
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• 2021

Recently, public certificates issued by nationally-recognized certification bodies have been abolished, and internet companies have issued their own common certificates as certification authority. The Electronic Signature Act was amended in a way to assign responsibility to Internet companies. As the use of a joint certificate issued by Internet companies as a certification authority is allowed, it is expected that the fraud damage caused by the theft of public key certificates will increase. We propose an authentication model that can be used in a security gateway that combines PKI with a blockchain with integrity and security. and to evaluate its practicality, we evaluated the security of the authentication model using Sugeno's hierarchical fuzzy integral, an evaluation method that excludes human subjectivity and importance degree using Delphi method by expert group. The blockchain-based joint certificate is expected to be used as a base technology for services that prevent reckless issuance and misuse of public certificates, and secure security and convenience.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.523-526
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• 2012

영상의 위변조를 탐지하거나 무결성을 인증하기 위해서는 가역 워터마킹 기법은 유용하다. 기존 워터 마킹 연구들은 원본 복원이 불가능하였으나, 가역 워터마킹은 워터마크를 검출한 후, 아무런 손상없이 영상을 원본 상태로 복원할 수 있는 방법이다. 본 논문에서는 차이값 히스토그램에 기반한 가역 워터 마킹을 통해 위변조된 영역을 탐지하는 블록단위 인증 알고리즘을 제안한다. 먼저, 영상 각 블록에 대하여 영상의 특징값을 추출하고, 사용자의 정보와 결합하여 인증 코드를 생성한다. 생성된 인증코드는 가역 워터마킹을 통하여 콘텐츠 자체에 직접 삽입한다. 영상의 인증을 위해서는 추출된 인증코드와 새로 생성된 인증코드의 비교를 수행한다. 다양한 영상들에 대하여 비교 분석하였고, 그 결과 제안한 알고리즘은 완전한 가역성과 함께 낮은 왜곡을 유지하면서도 97% 이상 인증률을 얻을 수 있었다.

• Journal of KIISE
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• v.42 no.1
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• pp.97-106
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• 2015

Recently, research on database encryption for data protection and query result authentication methods has been performed more actively in the database outsourcing environment. Existing database encryption schemes are vulnerable to order matching and counting attack of intruders who have background knowledge of the original database domain. Existing query result integrity auditing methods suffer from the transmission overhead of verification object. To resolve these problems, we propose a group-order preserving encryption index and a query result authentication method based on the encryption index. Our group-order preserving encryption index groups the original data for data encryption and support query processing without data decryption. We generate group ids by using the Hilbert-curve so that we can protect the group information while processing a query. Finally, our periodic function based data grouping and query result authentication scheme can reduce the data size of the query result verification. Through performance evaluation, we show that our method achieves better performance than an existing bucket-based verification scheme, it is 1.6 times faster in terms of query processing time and produces verification data that is 20 times smaller.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2002.11a
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• pp.551-554
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• 2002

인터넷 금융거래나 전자 상거래 등에서 인증, 기밀성, 부인방인, 무결성을 제공하기 위한 목적으로 PKI를 사용한다. PKI 시스템에 있어서 공개키 알고리즘의 공개키에 대한 CA 인증의 유효성이 중요하다. 현재 널리 사용되고 있는 CRL를 이용한 인증서의 검증은 CRL의 주기적인 발행으로 인해 인증서 폐지 정보를 실시간으로 인증서 사용자에게 전달할 수 없다는 단점이 있다. 본 논문에서는 CRL를 이용하여 인증서 검증을 하는 OCSP 서버와 CA사이에 인증서 상태정보를 전달하는 메커니즘을 제안함으로서 OCSP를 이용하여 인증서 검증을 하는 인증서 사용자에게 실시간 인증서 검증 서비스를 제공하고자 한다.