• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.1
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• pp.25-33
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• 2001

In 1998, A. Young and M. Yung introduced the concept of ARC that conjugates functionalities of a typical PKI with the ability to escrow privte keys of the system users. Also in 1999, P. Paillier and M. Yung proposed a new notion - called SE-PKI -which presents other additional advantages beyond ARC. But SE-PKI system uses only one escrow agent. The storage of users secret information at a single agent can make it significant point of attack and arouse controversy about invasion of privacy. This paper presents SE-PKI key recovery system that multiple escrow agents can participate in it. Also, in our system, escrow agents can\`t recover user\`s ciphertext.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.4
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• pp.111-122
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• 2008

Web service is defined to support interoperable machine to machine interaction over a network and defined as distributed technologies. Recently in web service environment, security has become one of the most critical issues. An attacker may expose user privacy and service information without authentication. Furthermore, the users of web services must temporarily delegate some or all of their behalf. This results in the exposure of user privacy information by agents. We propose a delegation model for providing safety of web service and user privacy in ubiquitous computing environments. In order to provide safety of web service and user privacy, XML-based encryption and a digital signature mechanism need to be efficiently integrated. In this paper, we propose web service management server based on XACML, in order to manage services and policies of web service providers. For this purpose, we extend SAML to declare delegation assertions transferred to web service providers by delegation among agents.

• Journal of KIISE:Information Networking
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• v.36 no.4
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• pp.263-274
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• 2009

Decentralized group key management mechanisms offer beneficial solutions to enhance the scalability and reliability of a secure multicast framework by confining the impact of a membership change in a local area. However, many of the previous decentralized solutions reveal the plaintext to the intermediate relaying proxies, or require the key distribution center to coordinate secure group communications between subgroups. In this study, we propose a decentralized group key management scheme that features a mechanism allowing a service provider to deliver the group key to valid members in a distributed manner using the proxy cryptography. In the proposed scheme, the key distribution center is eliminated while data confidentiality of the transmitted message is provided during the message delivery process. The proposed scheme can support a secure group communication in dynamic network environments where there is no trusted central controller for the whole network and the network topology changes frequently.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.534-536
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• 2014

CCTV의 다양한 필요성이 대두됨에 따라 CCTV를 통합관리하는 CCTV 통합관제 센터가 늘어나고 있다. 행정안전부는 2015년까지 전국 시군구에 CCTV 통합관제센터 구축을 추진하고 있을 정도로 앞으로도 계속적으로 증가할 예정이다. 하지만 이를 관리할 전문 모니터링 요원이 턱없이 부족한 상황이며, 전문 교육의 부재로 CCTV 영상을 개인적 호기심이나 개인의 이익을 위해 열람하는 경우가 발생하고 있다. 본 논문을 비밀 분산 기법을 이용하여 암호화된 키를 분배하고 요청에 따라 일정 수 이상의 분배키가 모이면 영상 열람권한을 주는 방식으로 설계 하여 관리자가 임의로 영상정보에 접근하는 상황을 방지하였다. 또한 그룹 키를 분배하고 수시로 키 갱신을 함으로서 다양한 보안 위협에 대응 하였다.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.4
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• pp.141-146
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• 2015

Data have been increased enormously due to the development of IT technology such as recent smart equipments, social network services and streaming services. To meet these environments the technologies that can treat mass data have received attention, and the typical one is Hadoop. Hadoop is on the basis of open source, and it has been designed to be used at general purpose computers on the basis of Linux. To initial Hadoop nearly no security was introduced, but as the number of users increased data that need security increased and there appeared new version that introduced Kerberos and Token system in 2009. But in this method there was a problem that only one secret key can be used and access permission to blocks cannot be authenticated to each user, and there were weak points that replay attack and spoofing attack were possible. Hence, to supplement these weak points and to maintain efficiency a protocol on the basis of group key, in which users are authenticated in logical group and then this is reflected to token, is proposed in this paper. The result shows that it has solved the weak points and there is no big overhead in terms of efficiency.

• Journal of Broadcast Engineering
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• v.20 no.4
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• pp.580-597
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• 2015

Broadcast encryption system is a cryptographic primitive that enables a sender to broadcast a message to a set of receivers in a secure channel. Out of previous proposed broadcast encryption systems, the most effective is the one that uses the Subset Difference(SD) method in a binary tree structure. The SD method has been realized by two underlying approaches: Pseudo-Random Generator(PRG) and Secret Sharing(SS). 2-SD method is the generalized version of the SD method by which two subsets of revoked receivers can be dealt with by one subset (in an SD-based broadcast encryption system). The primary advantage of the 2-SD method is to further reduce the size of transmission overhead, compared to the SD method. Until now, however, there is no known broadcast encryption system that is based on such a 2-SD technique using either PRG or SS basis. In this paper, we suggest a new 2-SD broadcast encryption system using the SS-based technique that was suggested by Jae Hwan Lee et al. in 2014[9]. The new system can reduce the size of ciphertext by 25% of the one in the previous SS-based broadcast encryption system. Also, on a theoretical note, ours is the first 2-SD broadcast encryption system that is provably secure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.116-128
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• 2005

The low-cost REID system is expected to be widely used in the ubiquitous computing environment as an intelligent device. Although REID systems have several advantages, they may create new threats to users' privacy. In this paper, a traceable and unlinkable REID system called 'Fair EPC system' is proposed for low-cost RFID tags. The proposed system enables the protection of users' privacy from unwanted scanning, and it is traceable to the tag by authorized administrators when necessary. The proposed system has some advantages; (1) eliminating any danger of exposing users' information via tag tracking through the cooperation between readers or back-end databases, (2) enabling the tracking of real serial number of the tag only through the cooperation of authorized administrators using a cryptographic secret sharing scheme, and (3) providing the efficiency of the proposed system reduce the computational workloads of back-end databases.