• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.648-651
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• 2013

클라우드 시스템에서는 데이터 소유자가 아닌 클라우드 서비스 제공자가 각 개인의 데이터에 대한 저장과 관리를 책임진다. 따라서 클라우드 서버 상의 사용자 데이터에 대한 보안을 보장해 주는 것이 가장 중요한 이슈이다. 데이터 보안 문제는 안전하고 효율적인 접근제어 기술을 통해 해결 할 수 있다. 기존 시스템에서 많이 이용되고 있는 RBAC(Role based access control)은 접근제어의 형태가 주로 수직적이고, 데이터 접근가능 여부를 역할이라는 고정적인 값에 따라 결정하기 때문에 동적인 클라우드 환경에 적합하지 않다. 반면 HASBE(Hierarchical attribute set based encryption) 모델은 ABAC(Attribute based access control)를 통해 유연하고 탄력적인 접근제어를 제공한다. 또한 HASBE 는 인가자(Authority)와 사용자의 관계 모델이 계층적인 구조를 갖고 있기 때문에 큰 조직에서 수많은 사용자들의 데이터 관리와 키 분배를 좀더 효율적으로 할 수 있다. 본 논문에서는 위의 계층적인 모델에서 더 나아가서, 실제 클라우드 환경에서 데이터가 가질 수 있는 복잡한 속성과 인가자의 관계를 고려해 다중 인가자의 개념이 더해진 모델을 제안한다.

• Journal of Convergence for Information Technology
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• v.8 no.3
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• pp.79-84
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• 2018

Cloud services are readily available through a variety of media, attracting a lot of attention from users. However, there are various security damages that abuse the privacy of users who use cloud services, so there is not enough technology to prevent them. In this paper, we propose a protection model to safeguard user's privacy in a cloud environment so as not to illegally exploit user's privacy. The proposed model randomly manages the user's signature to strengthen the role of the middle manager and the cloud server. In the proposed model, the user's privacy information is provided illegally by the cloud server to the user through the security function and the user signature. Also, the signature of the user can be safely used by bundling the random number of the multiplication group and the one-way hash function into the hash chain to protect the user's privacy. As a result of the performance evaluation, the proposed model achieved an average improvement of data processing time of 24.5% compared to the existing model and the efficiency of the proposed model was improved by 13.7% than the existing model because the user's privacy information was group managed.

• Journal of Korea Multimedia Society
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• v.11 no.1
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• pp.1-12
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• 2008

Database encryption is one of the important mechanisms for prohibiting internal malicious users and outside hackers from utilizing data. Frequent occurrences of encryption and decryption cause degradation of database performance so that many factors should be considered in implementing encryption system. In this paper, we propose an architecture of database encryption system and data encryption module. In addition we suggest extended SQL in order to manage data encryption and decryption. In implementing database encryption system, we adopt ARIA encryption algorithm which is proved to be the most fast one among Korea standardized encryption algorithm. We use an single key for each database in encrypting data rather than using several keys in order to improve performance. Research over performance evaluation of database encryption system is rare up to now. Based on our implemented system, we provide performance evaluation results over various H/W platforms and compare performance differences between plain text and encrypted data.

• Journal of Digital Convergence
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• v.14 no.6
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• pp.405-413
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• 2016

To solve various problems of the Internet as well as to enhance network performance, various future Internet architectures utilize cached data in network nodes or in proxy servers. Named-data networking (NDN), one of future Internet architectures, implements in-network data caching functionality, and then responds itself to request messages. However, it can cause users' privacy invasion that the publisher of data can not engage in the sharing/using process of the data anymore after the data was cached in-network. So NDN implements both encryption-based access control and group access control. But, since such access control schemes need to exchange additional messages in order to search for a proper access control list and keys, it causes inefficiency. This paper surveys the access control schemes of NDN, and then proposes an improved scheme.

• Journal of the Korea Society of Computer and Information
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• v.11 no.4 s.42
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• pp.147-154
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• 2006

Effective and efficient representation of color features of multiple video frames is an important vet challenging task for visual information management systems. This paper Proposes a Video Browsing Service(VBS) that provides both the video content retrieval and the video browsing by the real-time user interface on Web. For the scene segmentation and key frame extraction of video sequence, we proposes an efficient scene change detection method that combine the RGB color histogram with the X2 (Chi Square) histogram. Resulting key frames are linked by both physical and logical indexing. This system involves the video editing and retrieval function of a VCR's. Three elements that are the date, the need and the subject are used for video browsing. A Video Browsing Service is implemented with MySQL, PHP and JMF under Apache Web Server.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.747-754
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• 2016

DHCP(Dynamic Host Configuration Protocol) is a protocol for efficiency and convenience of the IP address management. DHCP automatically assigns an IP address and configuration information needed to run the TCP/IP communication to individual host in the network. However, existing DHCP is vulnerable for network attack such as DHCP spoofing, release attack because there is no mutual authentication systems between server and client. To solve this problem, we have designed a new DHCP protocol supporting the following features: First, ECDH(Elliptic Curve Diffie-Hellman) is used to create session key and ECDSA(Elliptic Curve Digital Signature Algorithm) is used for mutual authentication between server and client. Also this protocol ensures integrity of message by adding a HMAC(Hash-based Message Authentication Code) on the message. And replay attacks can be prevented by using a Nonce. As a result, The receiver can prevent the network attack by discarding the received message from unauthorized host.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.1
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• pp.5-14
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• 2018

With the advance of the 4th industrial revolution, Internet of Things (IoT) technology is actively being studied. In the era of the IoT, a decentralized operation is required to reduce load on servers and enable autonomous IoT data communication rather than focusing on centralized operation of being server client structures. This paper analyzes the security of a blockchain, a new form of distributed database platform that supports integrity and permanence of data. To achieve this, we divide the blockchain's major operations into a consensus process, network communication process, and key management process, and then describe possible attacks and countermeasures in each process. We also describe the attack occurred in typical cryptocurrency platforms such as Bitcoin and Ethereum.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.1
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• pp.87-97
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• 2005

A secure index search protocol let us search the index of encrypted documents using the trapdoor for a keyword. It enables an untrusted server to learn nothing more than the search result about the documents without revealing the keyword. A lot of secure search protocols have been suggested but they only considered the search between a single-user and a server. In real organizations such as government offices or enterprises where exist many hierarchical departments, the search system for groups is arisen more often. In this paper, we construct secure index search protocols for hierarchical group settings without re-encryption of the old encrypted documents when group keys are re-keyed newly.

• Journal of Digital Contents Society
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• v.9 no.1
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• pp.125-130
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• 2008

User web service is increasing by development of internet technology. Quantity of encrypted data that transmitted through the network are increasing by development of encipherment technology. We have many problems; it is caused by technical development and service increase of user requests. It is like that, we have reliability of contents and illegality copy problem of internet contents in web application system. It is contents protection skills in web that encipherment technology, authentication and digital signature. We need message encoding and secret key for solve vulnerability of encipherment in web application system. In this paper, we propose a distributed secure system that can data confidentiality and user authentication. It prevent performance degradation from bottle neck in encipherment server, and improve service quality.

• Convergence Security Journal
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• v.11 no.6
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• pp.37-44
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• 2011

VANET(Vehicular Ad-hoc Network) is a kind of ad hoc networks consist of intelligence vehicular ad nodes, and has become a hot emerging research project in many field. It provide traffic safety, cooperative driving and etc. but has also some security problems that can be occurred in general ad hoc networks. Also, in VANET, vehicles shoul d be able to authenticate each other to securely communicate with network-based infrastructure, and their locations and identifiers should not be exposed from the communication messages. This paper proposes V2I(Vehicular to Infra structure) authentication protocol that anonymity and untraceability of vehicular using Error Correcting Code that ge nerate encoding certification using generation matrix. The proposed scheme based on ECC resolves overhead problems of vehicular secure key management of KDC.