• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.1
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• pp.123-132
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• 2015

In cloud storage, processing the duplicated data, namely deduplication, is necessary technology to save storage space. Users who store sensitive data in remote storage want data be encrypted. However Cloud storage server do not detect duplication of conventionally encrypted data. To solve this problem, Convergent Encryption has been proposed. But it inherently have weakness due to brute-force attack. On the other hand, to save storage space as well as save bandwidths, client-side deduplication have been applied. Recently, various client-side deduplication technology has been proposed. However, this propositions still cannot solve the security problem. In this paper, we suggest a secure source-based deduplication technology, which encrypt data to ensure the confidentiality of sensitive data and apply proofs of ownership protocol to control access to the data, from curious cloud server and malicious user.

• The KIPS Transactions:PartA
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• v.15A no.4
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• pp.199-210
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• 2008

A Clustering based wireless internet proxy server needs a layer-7 load balancer with URL hashing methods to reduce the total storage space for servers. Layer-4 load balancer located in front of server cluster is to distribute client requests to the servers with the same contents at transport layer, such as TCP or UDP, without looking at the content of the request. Layer-7 load balancer located in front of server cluster is to parse client requests in application layer and distribute them to servers based on different types of request contents. Layer 7 load balancer allows servers to have different contents in an exclusive way so that it can minimize the total storage space for servers and improve overall cluster performance. However, its scalability is limited due to the high overhead of parsing requests in application layer as different from layer-4 load balancer. In order to overcome its scalability limitation, in this paper, we propose a distributed layer-7 load balancer by replacing a single layer-7 load balancer in the conventional scheme by a single layer-4 load balancer located in front of server cluster and a set of layer-7 load balancers located at server cluster. In a clustering based wireless internet proxy server, we implemented the conventional scheme by using KTCPVS(Kernel TCP Virtual Server), a linux based layer-7 load balancer. Also, we implemented the proposed scheme by using IPVS(IP Virtual Server), a linux-based layer-4 load balancer, installing KTCPVS in each server, and making them work together. We performed experiments using 16 PCs. Experimental results show scalability and high performance of the proposed scheme, as the number of servers grows, compared to the conventional scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.1
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• pp.83-94
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• 2015

Deduplication, which is a technique of eliminating redundant data by storing only a single copy of each data, provides clients and a cloud server with efficiency for managing stored data. Since the data is saved in untrusted public cloud server, however, both invasion of data privacy and data loss can be occurred. Over recent years, although many studies have been proposed secure deduplication schemes, there still remains both the security problems causing serious damages and inefficiency. In this paper, we propose secure and efficient client-side deduplication with Key-server based on Bellare et. al's scheme and challenge-response method. Furthermore, we point out potential risks of client-side deduplication and show that our scheme is secure against various attacks and provides high efficiency for uploading big size of data.

• Journal of the Korea Society for Simulation
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• v.16 no.2
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• pp.9-15
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• 2007

As the Internet grows and the mass multimedia data become popular, the storage system migrates from DAS, where the storage and the server are directly connected, to SAN and NAS. SAN connects the storages with a separate network, and NAS provides only file services, connects the storages with IP network. However, SAN and NAS can not fulfill the needs for companies if used separately, thus are asked to be integrated. In this research, we propose an efficient data sharing method which employees the concept of GMC, Croup Master Cache for the integrated environment of SAN and NAS. GMC is based on MCI, Metadata server and Cluster system Integration, but tries to solve the high expansion cost problem with MCI. We introduce the basic concept of GMC, compare the performance of GMC with that of MCI using computer simulation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.330.1-330.1
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• 2014

개인용 노트북, 태블릿 PC, 핸드폰 기술 발전에 의해 언제 어디서나 데이터를 작성하고 기록하는 일들이 가능해졌다. 특히 cloud 시스템을 이용하여 데이터를 휴대기기에 직접 저장하지 않고 server에 기록하는 일들이 가능해짐에 따라 server 기기의 성능, server-room power 및 space 에 대한 관심이 증가하였다. Storage class memory (SCM) 이란 memory device와 storage device의 장점을 결합한 memory를 일컫는 기술로 현재 소형 디바이스 부분부터 점차 그 영역을 넓히고 있다. 그중 phase change material을 이용한 phase change memory (PCM) 기술이 가장 각광받고 있다. PCM의 경우 scaling됨에 의해 cell간의 열 간섭으로 인한 data 손실의 우려가 있어 cell의 면적을 최소화 하여 소자를 제작하여야 한다. 기존의 sputtering등의 PVD 방법으로는 한계가 있어 ALD 공정을 이용한 PCM에 대한 연구가 활발히 진행중이다. 특히 tellurium 원료기체로 silyl 화합물 [1]을 사용하여 주로 $Ge_2Sb_2Te_5$의 조성에 초점을 맞춰 진행되고 있으나, 세부 공정에 대한 기본적인 연구는 미비하다. 본 연구에서는 Ge-Sb-Te 3원계 박막을 형성하기 위한 Sb-Te 화합물의 증착 공정에 대한 연구를 수행하였다. 특히 원료기체로 Si이 없는 새로운 Te 원료기체를 이용하여 조성 조절을 하였고, 박막의 물성을 분석하였다. 또한 공정온도에 따른 박막의 물성 변화를 분석하였다.

• Journal of KIISE
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• v.43 no.2
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• pp.143-151
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• 2016

Data deduplication is an important technique for cloud storage savings. These techniques are especially important for encrypted data because data deduplication over plaintext is basically vulnerable for data confidentiality. We examined encrypted data deduplication with the aid of a key issuing server and compared Convergent Encryption with a technique created by M.Bellare et al. In addition, we implemented this technique over not only Dropbox but also an open cloud storage service, Openstack Swift. We measured the performance for this technique over Dropbox and Openstack Swift. According to our results, we verified that the encrypted data deduplication technique with the aid of a key issuing server is a feasible and versatile method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.11-15
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• 2015

SSD(Solide State Disk) Memory is gradually replacing HDD(Hard Disk Drive) for high speed data input and output processing on Internet server system. In this paper, we proposed efficient data distribution storage algorithm in DRAM based SSD. And we did performance test for proposed algorithm and existing algorithm in the same server environment condition. The result of comparison of performance test is as fellows. Data backup processing time of proposed algorithm was reduced by half than that of existing algorithm.

• Journal of Information Processing Systems
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• v.15 no.1
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• pp.151-158
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• 2019

With the recent advances of memory technologies, high-performance non-volatile memories such as non-volatile dual in-line memory module (NVDIMM) have begun to be used as an addition or an alternative to server-side storages. When these memory bus-connected storages (MBSs) are installed over non-uniform memory access (NUMA) servers, the distance between NUMA nodes and MBSs is one of the crucial factors that influence file processing performance, because the access latency of a NUMA system varies depending on its distance from the NUMA nodes. This paper presents the design and implementation of a high-performance logical volume manager for MBSs, called MBS-LVM, when multiple MBSs are scattered over a NUMA server. The MBS-LVM consolidates the address space of each MBS into a single global address space and dynamically utilizes storage spaces such that each thread can access an MBS with the lowest latency possible. We implemented the MBS-LVM in the Linux kernel and evaluated its performance by porting it over the tmpfs, a memory-based file system widely used in Linux. The results of the benchmarking show that the write performance of the tmpfs using MBS-LVM has been improved by up to twenty times against the original tmpfs over a NUMA server with four nodes.

• Journal of Software Assessment and Valuation
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• v.15 no.2
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• pp.95-100
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• 2019

In this paper, we propose a simple hardware reporting method for errors in soft-RAID systems of Linux OS. Compared with other reporting methods, the proposed method displays error status intuitively without any additional access process such as log-in process or home-page access. In particular, the server actively displays the error status, so the administrator can take immediate action. In order to confirm the effectiveness of the proposed method, the experimental circuit was constructed and the experimental results showed that the error was actively displayed when an error occurred in the storage device. As such, a soft-RAID system can perform almost the same function as a hardware RAID system, thereby ensuring server data reliability at low cost.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1553-1557
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• 2005

High performance and reliability of the storage system to handle a very large amount of data has been become very important. Many techniques have been applied on the various application systems to establish very large capacity storage that satisfy the requirement of high I/O speed and physical or logical failure protection. We applied RAID and LVM to construct a storage system for the global data center which needs a very reliable large capacity storage system. The storage system is successfully established and equipped on the latest Linux application server.