• The KIPS Transactions:PartC
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• v.11C no.5
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• pp.585-594
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• 2004

When several service providers want to work together with only one master key, they need to properly distribute the key to participants who come in for the co-work business and then securely manage the distributed keys. This paper describes the system that can efficiently and securely manage the master key on the basis of the secret sharing scheme that can reconstruct original secret information as the necessity of reconstructing original secret arises. The proposed system can distribute secret information to several groups and also redistribute the secret to subgroup in proportion to the participant's security level using smart card-based (t, t)-(k, n)-threshold secret scheme for securely keeping secret information and authentication of participant's identification.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.4028-4049
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• 2014

Attribute-based encryption (ABE) is a promising cryptographic primitive for implementing fine-grained data sharing in cloud computing. However, before ABE can be widely deployed in practical cloud storage systems, a challenging issue with regard to attributes and user revocation has to be addressed. To our knowledge, most of the existing ABE schemes fail to support flexible and direct revocation owing to the burdensome update of attribute secret keys and all the ciphertexts. Aiming at tackling the challenge above, we formalize the notion of ciphertext-policy ABE supporting flexible and direct revocation (FDR-CP-ABE), and present a concrete construction. The proposed scheme supports direct attribute and user revocation. To achieve this goal, we introduce an auxiliary function to determine the ciphertexts involved in revocation events, and then only update these involved ciphertexts by adopting the technique of broadcast encryption. Furthermore, our construction is proven secure in the standard model. Theoretical analysis and experimental results indicate that FDR-CP-ABE outperforms the previous revocation-related methods.

• International Journal of Computer Science & Network Security
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• v.21 no.1
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• pp.174-183
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• 2021

The advent of social media has revolutionized the speed of communication between millions of people around the world in various cultures and disciplines. Social media is the best platform for exchanging opinions and ideas, interacting with other users of similar interests and sharing different types of media and files. With the phenomenal increase in the use of social media platforms, the need to pay attention to protection and security from attacks and misuse has also increased. The present study conducts a comprehensive survey of the latest and most important research studies published from 2018-20 on security and privacy on social media and types of threats and attacks that affect the users. We have also reviewed the recent challenges that affect security features in social media. Furthermore, this research pursuit also presents effective and feasible solutions that address these threats and attacks and cites recommendations to increase security and privacy for the users of social media.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.973-976
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• 2015

Inernet of Things(IoT) is interaction with each other, collecting, sharing, and analysing the data. IoT has been noted in combining the fields of medical service in particular. However, the security issue is caused, while IoT is receiving attention. U-Health and medical devices, which deal mainly the personal health information, is required to a high level of privacy and security of health information. This study analyzes cases of leakage of personal medical information, security of IoT, privacy flow, and the response strategies.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.5
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• pp.951-958
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• 2021

With the growing cyber threat to information assets, it has become important to share threat information quickly. This paper examines the sharing of cyber threat information and presents a method to determine the importance of threat indicators in the information sharing market by calculating weights. The analysis was conducted using AHP techniques, with a pairwise comparison of the four factors(attacker & infected system indicators, role indicators, malicious file indicators, technique & spread indicators) and the details of each factor. Analysis shows that malicious file indicators are the most important among the higher evaluation factors and infected system IP, C&C and Smishing are the most important factors in comparison between detailed items. These findings could be used to measure the preference of consumers and the contribution of information provider for facilitating information sharing.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.3
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• pp.131-141
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• 2011

OMA(Open Mobile Alliance) is one of the most active group about DRM technology in mobile device field. OMA announced an OMA-DRM v 2.1 standardization in 2007. After then OMA announced OMA-SRM(Secure Removable Media) and SCE(Secure Contents Exchanges) that are the extension of OMA-DRM v2.1. In SCE, a user can form user domain to share contents and rights. So the user can share contents and rights with not only the the OMA-DRM v2.1 but also home devices like mobile phones, personal computers and audios. In this paper, we analyze a sharing technology of OMA-DRM and SCE, and then propose key distribution method using proxy re-encryption and smart card to use shared contents and rights.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.13-20
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• 2003

웹 서비스는 기존 분산 처리기술과 인터넷 기술에 기반한 기술이며, 이기종 시스템간의 데이터를 자연스럽게 공유하고 통신하는 것을 목적으로 등장한 기술이다. 또한 웹서비스 기술로 구현된 프로그램은 필요한 곳에서 proxy object를 생성해서 사용할 수 있으므로, 다른 개발 환경에서 작성된 프로그램이라도 호출해서 사용할 수 있게 되었다. 본 논문에서는 프로그램을 공유하는 과정에서 발생할 수 있는 보안 요구사항을 도출해보고 보안을 위해 XML Signature와 XML Encryption을 적용한 안전한 프로그램 공유 시스템을 제시해 본다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.287-290
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• 2006

디지털 기술의 발전으로 인해 원본과 동일한 품질을 가지는 디지털 콘텐츠의 무한한 복제가 가능할 뿐만 아니라 인터넷을 통해 전 세계 어디라도 전파될 수 있다. 이러한 디지털 콘텐츠의 불법복제에 따른 문제를 해결해 줄 수 있는 것이 바로 DRM(Digital Rights Management)이다. 하지만 현재의 DRM은 콘텐츠를 구매하여 License를 받은 최초의 디바이스에서만 사용이 가능하도록 설계 되어 있다. 이러한 방식은 콘텐츠를 구매한 사용자의 권리를 제한하는 것이다. 본 논문에서는 Home Network와 같은 특정 Domain영역 안에서만 콘텐츠의 사용이 가능한 DRM 시스템을 제안한다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.3
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• pp.18-26
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• 2011

Social network services whose users increase rapidly is the online services that reflect social network. They are used for various purposes such as strategy of election, commercial advertisement and marketing, educational information sharing and exchange of medical knowledge and opinions. These services make users form social networks with other users who have common interests and expand their relationships by releasing their personal information and utilizing other users' social networks. However, the social network services based on open and sharing of information raise various security threats such as violation of privacy and phishing. In this paper, we propose a group key management scheme and protocols using key rings to protect communication of small groups in social network services.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.1
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• pp.266-286
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• 2022

Public key encryption with keyword search (PEKS) allows a user to make search on ciphertexts without disclosing the information of encrypted messages and keywords. In practice, cryptographic operations often occur on insecure devices or mobile devices. But, these devices face the risk of being lost or stolen. Therefore, the secret keys stored on these devices are likely to be exposed. To handle the key exposure problem in PEKS, the notion of key-updatable PEKS (KU-PEKS) was proposed recently. In KU-PEKS, the users' keys can be updated as the system runs. Nevertheless, the existing KU-PEKS framework has some weaknesses. Firstly, it can't update the keyword ciphertexts on the storage server without leaking keyword information. Secondly, it needs to send the search tokens to the storage server by secure channels. Thirdly, it does not consider the search token security. In this work, a new PEKS framework named key-updatable and ciphertext-sharable PEKS (KU-CS-PEKS) is devised. This novel framework effectively overcomes the weaknesses in KU-PEKS and has the ciphertext sharing function which is not supported by KU-PEKS. The security notions for KU-CS-PEKS are formally defined and then a concrete KU-CS-PEKS scheme is proposed. The security proofs demonstrate that the KU-CS-PEKS scheme guarantees both the keyword ciphertext privacy and the search token privacy. The experimental results and comparisons bear out that the proposed scheme is practicable.