• Proceedings of the Korea Information Processing Society Conference
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• 2000.10a
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• pp.837-840
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• 2000

For secure communications in using multicast applications such as Cable-TV, It is essential for us to manage shared keys to encrypt/decrypt data through crypto algorithm as DES, which is called Group Key Management. In GKM, It is a hot issue that reduces the number of join/leave operation and subgroup key in key tree model. In this paper, we propose optimized mechanism of group key management required for providing multicast security.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.1
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• pp.3-13
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• 2004

E-Commerce is suddenly spreading in a daily life. A rights trading system is a system that circulates digital-tickets such as plane tickets, software license, coupon. There are two main approaches so far account-based and smart-card based systems. The NTT Proposed FlexToken, a new smart card based copy prevention scheme for digital rights. They Proposed using pseudonymous self certified keys of Petersen and Horster in order to ensure anonymity of users. However. Petersen and Holster's scheme should register a pseudonymous key pair at TTP (One-time) every time so that users create the signature which is satisfied with unlinkability property In this paper, we propose a new anonymous rights trading system using group signature. This paper has a meaning having applied to digital rights trading system an efficient smart card based group signature.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.235-246
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• 2002

While the Internet is suffering from the massive data such as video stream, IP multicast can ease the load of the Internet by enabling one copy of digital information to be received by multiple computers simultaneously. But If multicast is based on UDP, packets are delivered using a best-effort Policy without any reliability, congestion control or flow control. Multicast group members can join or leave a multicast group at will, and multicast uses broadcast mechanism, it's very hard to keep security from unauthorized members. In this paper, we introduce a new reliable multicast protocol TRDMF proper for one-to-many multicast model with reliability, flow control, congestion control and key management.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.3
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• pp.119-131
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• 2009

The world's widely used key exchange protocols are open cryptographic communication protocols, such as TLS/SSL, whereas in the financial field in Korea, key exchange protocols developed by industrial classification group have been used that are based on PKI(Public Key Infrastructure) which is suitable for the financial environments of Korea. However, the key exchange protocols are not only vulnerable to client impersonation attacks and known-key attacks, but also do not provide forward secrecy. Especially, an attacker with the private keys of the financial security server can easily get an old session-key that can decrypt the encrypted messages between the clients and the server. The exposure of the server's private keys by internal management problems, etc, results in a huge problem, such as exposure of a lot of private information and financial information of clients. In this paper, we analyze the weaknesses of the cryptographic communication protocols in use in Korea. We then propose two key exchange protocols which reduce the replacement cost of protocols and are also secure against client impersonation attacks and session-key and private key reveal attacks. The forward secrecy of the second protocol is reduced to the HDH(Hash Diffie-Hellman) problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.5
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• pp.410-415
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• 2013

Recently, as Internet enters WEB 2.0, many social network services through such as Facebook, Twitter and Youtube appeared. In these social network sites, users can easily make friends, join groups and access others personal information. Therefore, a malicious user can easily gather information of others. In order to protect user's personal information from the unauthenticated users, we propose privacy protection mechanism based on key assignment and user's trust level. A master-key is generated for each users and is segmented into a core-key and several sub-key. The master-key stores at the information owner's side and the sub-key will be distributed to requestor according to the relation and trust level. At last, in order to proof the efficiency, the performance of our proposed mechanism is compared with those of existing mechanisms.

• Journal of the Korean Society for information Management
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• v.32 no.3
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• pp.377-396
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• 2015

This study proposed a key-frame automatic extraction method for video storyboard surrogates based on users' cognitive responses, EEG signals and discriminant analysis. Using twenty participants, we examined which ERP pattern is suitable for each step, assuming that there are five image recognition and process steps (stimuli attention, stimuli perception, memory retrieval, stimuli/memory comparison, relevance judgement). As a result, we found that each step has a suitable ERP pattern, such as N100, P200, N400, P3b, and P600. Moreover, we also found that the peak amplitude of left parietal lobe (P7) and the latency of FP2 are important variables in distinguishing among relevant, partial, and non-relevant frames. Using these variables, we conducted a discriminant analysis to classify between relevant and non-relevant frames.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.5
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• pp.45-57
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• 2009

In this paper, we implemented the conference system based on DTLS for saving securely the VoIP, which is served sprightly in the latest, securely and tested (and also analyzed) the system. As VoIP technology development, demand of conference system is increased and the related technologies are growed. But Security protocol to protect conference service is getting late than conference technology. In this paper, we studied based on DTLS protocol that can provide function of signaling, channel security, media channel security and application of group key and apply to VoIP conference system based UDP unchanged. In this paper, we searched suggested security protocols based on DTLS can apply to conference system and implement and apply the protocol to conference system. And we tested (and also alayzed) overhead of encryption and key management mechanism.

• The Journal of the Korea Contents Association
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• v.19 no.5
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• pp.187-193
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• 2019

Key-value storage engines are an essential component of growing demand in many computing environments, including social networks, online e-commerce, and cloud services. Recent key-value storage engines offer many features such as transaction, versioning, and replication. In a key-value storage engine, transaction processing provides atomicity through Write-Ahead-Logging (WAL), and a synchronous commit method for transaction processing flushes log data before the transaction completes. According to our observation, flushing log data to persistent storage is a performance bottleneck for key-value storage engines due to the significant overhead of fsync() calls despite the various optimizations of existing systems. In this article, we propose a group synchronization method to improve the performance of the key-value storage engine. We also design and implement a transaction scheduling method to perform other transactions while the system processes fsync() calls. The proposed method is an efficient way to reduce the number of frequent fsync() calls in the synchronous commit while supporting the same level of transaction provided by the existing system. We implement our scheme on the WiredTiger storage engine and our experimental results show that the proposed system improves the performance of key-value workloads over existing systems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.10
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• pp.40-48
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• 2008

Security of self organized mobile ad hoc networks is an important issue because administration information in the networks is managed by the constituent nodes. Especially authentication mechanism is necessary for trust setup between newly joining nodes and the network. The authentication models and protocols which are based on the wireline infrastructure could not be practical for mobile ad hoc network. Although public key algorithm-based method is widely used for authentication, it is not easy to be applied to mobile ad hoc networks because they do not have infrastructure such as centralized CA which is needed for certificate verification. In this paper, we consider the public key based random CA group method proposed in [1] to provide efficient authentication scheme to mobile ad hoc networks and analyze the performance of the method, which is then compared to the home CA method. From the analysis results, we see that the random CA method where the function of CA is distributed to some mobile nodes and the authentication information is propagated to randomly chosen CAs shows higher reliability and lower cost than home CA method.

• 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.