• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3086-3092
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• 2014

The FTP that provides file transfer capabilities to/from another station cannot provides data confidentialities. The FTPS and SFTP can support a security functionalities. The FTPS needs a SSL layer and SFTP use a functions of SSH. And therefore the FTPS or SFTP needs an additional modules such as SSL or SSH. In this paper, we propose a new Secured FTP protocol that can support the security functions without extra security system. The Secured FTP uses Diffie-Hellman key agreement algorithm for shared secret key generation and AES-Counter algorithm for data encryption algorithm. Our designed Secured FTP is implemented in Linux environments and the proper operations of implemented Secured FTP is verified.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.12C
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• pp.1238-1244
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• 2002

In this paper, H.235-based security mechanism for H.323 multimedia applications was implemented. H.235 covers authentication using HMAC, Diffie-Hellman key exchange, session key management for voice channel, and encryption functions such as DES, 3DES, RC2. Extra encryption algorithms such as SEED, and AES were also included for possible use in the future. And, we also analyzed the quality of service (QoS), the requirement of implementation, and interoperability to the result in this study. The results could be applied to secure simple IP phone terminals, gateways, or gatekeepers.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.49-59
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• 2018

Smart grid system has been deployed fast despite of legal, business and technology problems in many countries. One important problem in deploying the smart grid system is to protect private smart meter readings from the unbelievable parties while the major smart meter functions are untouched. Privacy-preserving involves some challenges such as hardware limitations, secure cryptographic schemes and secure signal processing. In this paper, we focused particularly on the smart meter reading aggregation,which is the major research field in the smart meter privacy-preserving. We suggest a noisy weighted aggregation scheme to guarantee differential privacy. The noisy weighted values are generated in such a way that their product is one and are used for making the veiled measurements. In case that a Diffie-Hellman generator is applied to obtain the noisy weighted values, the noisy values are transformed in such a way that their sum is zero. The advantage of Diffie and Hellman group is usually to use 512 bits. Thus, compared to Paillier cryptosystem series which relies on very large key sizes, a significant performance can be obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.977-983
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• 2010

In mobile and secure military networks, full-meshed IPSec tunnels, which do correspond to not physical links but logical links between each IPSec device and its peer, are required to provide multicast communications. All IPSec devices need support in changing IPSec tunnels by a way of using a multicast group key which is updated dynamically. Tactical terminals, which often constitute a group, need also secure multicast communications in the same group members. Then, the multicast group key is required to be updated dynamically in order to support group members' mobility. This paper presents challenging issues of designing a secure and dynamic group key management of which concept is based on the Diffie-Hellman (DH) key exchange algorithm and key trees. The advantage of our dynamic tree based key management is that it enables the dynamic group members to periodically receive status information from every peer members and effectively update a group key based on dynamically changing environments.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.5
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• pp.73-92
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• 2005

Joux's tripartite key agreement protocol is one of the most prominent developments in the area of key agreement. Although certificate-based and ID-based authentication schemes have been proposed to provide authentication for Joux's protocol, no provably secure password-based one round tripartite key agreement protocol has been proposed yet. We propose a secure one round password-based tripartite key agreement protocol that builds on Joux's protocol and adapts PAK-EC scheme for password-based authentication, and present a proof of its security.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11c
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• pp.1759-1762
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• 2003

최근 키 분배 프로토콜과는 다르게 하드웨어에 암호키를 저장하여 사용하는 것과 달리, 사용자가 기억할 수 있는 길이의 패스워드(password)를 사용해 서버와의 인증과 키 교환을 동시에 수행하는 패스워드 기반 키 분배 프로토콜이 제안되고 있다. 본 논문에서는 이러한 패스워드 기반의 키 분배 프로토콜 중 BPKA(Balanced Password-authenticated Key Agreement)에 속하는 DH-EKE(Diffie-Hellman Encrypted Key Exchange), PAK(Password-Authenticated Key exchange), SPEKE(Simple Password Exponential Key Exchange) 프로토콜을 비교 분석하고, 이를 바탕으로 기존의 BPKA 프로토콜에 비해 적은 연산량을 가지면서 사용자와 서버가 각기 다른 정보를 갖는 패스워드-검증자 기반 프로토콜을 제안한다. 본 논문에서 제안하는 패스워드 기반 키 분배 프로토콜의 안전성 분석을 위해 Active Impersonation 과 Forward Secrecy, Off-line dictionary attack, Man-in-the -middle Attack 등의 공격모델을 적용하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.6
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• pp.23-35
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• 2009

Password-Authenticated Key Exchange (PAKE) Protocol is a useful tool for secure communication conducted over open networks without sharing a common secret key or assuming the existence of the public key infrastructure (PKI). It seems difficult to design efficient PAKE protocols using RSA, and thus many PAKE protocols are designed based on the Diffie-Hellman key exchange (DH-PAKE). Therefore it is important to design an efficient PAKE based on RSA function since the function is suitable for designing a PAKE protocol for imbalanced communication environment. In this paper, we propose a computationally-efficient key exchange protocol based on the RSA function that is suitable for low-power devices in imbalanced environment. Our protocol is more efficient than previous RSA-PAKE protocols, required theoretical computation and experiment time in the same environment. Our protocol can provide that it is more 84% efficiency key exchange than secure and the most efficient RSA-PAKE protocol CEPEK. We can improve the performance of our protocol by computing some costly operations in offline step. We prove the security of our protocol under firmly formalized security model in the random oracle model.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2002.11a
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• pp.479-486
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• 2002

본 논문에서는 국내 광대역 위성 액세스 망(BSAN: Broadband Satellite Access Network) 에 적용 가능한 보안 기능을 위한 가이드 라인을 살펴보고, RCST와 NCC간에 인증 및 키 관리 기능을 위하여 요구되는 주요 핵심 보안 메커니즘에 기술한다. 더불어 국내 광대역 위성 액세스망을 위한 가이드라인을 기술하고, ETSI 표준을 분석한다. 기종 표준안의 키 공유 프로토콜은 키의 신선도와 확신성을 제공하지 않는다. 따라서 본 논문에서는 키의 신선도와 확신성을 갖으면서 계산적 복잡도와 교환되는 데이터 량을 감소시키기 위한 세 가지 키분배 프로토콜을 제안하고 제안된 프로토콜의 특성을 비교 분석한다. 특히 이러한 특성을 갖는 ECDH(Elliptic Curve Diffie-Hellman)키 공유 프로토콜을 제안한다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1994.11a
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• pp.263-274
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• 1994

협대역 ISDN은 사용자-망 인터페이스가 디지탈화되므로 사용자 정보를 보호하기 위한 기능을 비교적 저렴하게 사용자-망 인터페이스에서 제공할 수 있다. 그러나 음성, 화상, 데이타 등 정보의 종류가 다양하고 여러 채널을 통한 다양한 서비스 기능이 있으므로 실제적인 구현에는 많은 어려움이 따른다. 이러한 문제들을 고려하여 본 논문에서는 ISDN 사용자 정보의 비밀보장 서비스를 위한 키 분배 및 인증 방법을 제안하였다. 따라서 먼저 ITU-T(구 CCITT) 권고안의 표준을 중심으로 ISDN 사용자-망 인터페이스의 구조와 ISDN의 각종 서비스에서 우려되는 정보침해 요소론 분석한 후, 이 분석 자료를 근간으로 하여 비밀보장 서비스를 위한 기본적인 정책을 수립하고 적합한 프로토콜 구조를 제안하였다. 그리고 Diffie-Hellman이 제안한 공개키 분배방식을 기반으로 하여, 호(Call)설정시 Q.931 메세지 교환을 통하여 키 분배 및 인증이 안전하게 이루어지도록 적합한 키 분배 프로토콜을 제안하였으며, 키의 분배 및 인증의 명확성 여부를 GNY 로직을 이용하여 검증하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.1
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• pp.59-69
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• 2004

Password-based authenticated group key exchange protocols provide a group of user, communicating over a public(insecure) channel and holding a common human-memorable password, with a session key to be used to construct secure multicast sessions for data integrity and confidentiality. In this paper, we present a password-based authenticated group key exchange protocol and prove the security in the random oracle model and the ideal cipher model under the intractability of the decisional Diffie-Hellman(DH) problem and computational DH problem. The protocol is scalable, i.e. constant round and with O(1) exponentiations per user, and provides forward secrecy.