• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권11호
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• pp.2941-2956
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• 2013

In this paper, we propose an effective fragile image watermarking scheme for tampering detection and content recovery. Cover image is divided into a series of non-overlapping blocks and a block mapping relationship is constructed by the secret key. Several DCT coefficients with direct current and lower frequencies of the MSBs for each block are used to generate the reference bits, and different coefficients are assigned with different bit numbers for representation according to their importance. To enhance recovery performance, authentication bits are generated by the MSBs and the reference bits, respectively. After LSB substitution hiding, the embedded watermark bits in each block consist of the information of itself and its mapping blocks. On the receiver side, all blocks with tampered MSBs can be detected and recovered using the valid extracted reference bits. Experimental results demonstrate the effectiveness of the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.2235-2253
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• 2011

Digital document file such as Adobe Acrobat or MS-Office is encrypted by its own ciphering algorithm with a user password. When this password is not known to a user or a forensic inspector, it is necessary to recover the password to open the encrypted file. Password cracking by brute-force search is a perfect approach to discover the password but a time consuming process. This paper presents a new method of speeding up password recovery on Graphic Processing Unit (GPU) using a Compute Unified Device Architecture (CUDA). PDF files are chosen as a password cracking target, and the Abode Acrobat password recovery algorithm is examined. Experimental results show that the proposed method gives high performance at low cost, with a cluster of GPU nodes significantly speeding up the password recovery by exploiting a number of computing nodes. Password cracking performance is increased linearly in proportion to the number of computing nodes and GPUs.

• 한국IT서비스학회지
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• 제11권3호
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• pp.1-16
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• 2012

This paper is aimed to present a fuzzy decision-making approach to deal with disaster recovery priority decision problem in information system. We derive an evaluation approach based on TOPSIS(Technique for Order Performance by Similarity to Ideal Solution), to help disaster recovery priority decision of total information system for port logistics in a fuzzy environment where the vagueness and subjectivity are handled with linguistic terms parameterized by trapezoidal fuzzy numbers. This study applies the fuzzy multi-criteria decision-making method to determine the importance weight of evaluation criteria and to synthesize the ratings of candidate disaster recovery system. Aggregated the evaluators' attitude toward preference, then TOPSIS is employed to obtain a crisp overall performance value for each alternative to make a final decision. This approach is demonstrated with a real case study involving 4 evaluation criteria(system dependence, RTO, loss, alternative business support), 7 information systems for port logistics assessed by 5 evaluators from Maritime Affairs and Port Office.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권3호
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• pp.1280-1300
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• 2020

In the modern financial sector, interest in providing financial services that employ blockchain technology has increased. Blockchain technology is efficient and can operate without a trusted party to store all transaction information; additionally, it provides transparency and prevents the tampering of transaction information. However, new security threats can occur because blockchain technology shares all the transaction information. Furthermore, studies have reported that the private keys of users who use the same signature value two or more times can be recovered. Because private keys of blockchain identify users, private key leaks can result in attackers stealing the ownership rights to users' property. Therefore, as more financial services use blockchain technology, actions to counteract the threat of private key recovery must be continually investigated. Private key recovery studies are presented here. Based on these studies, duplicated signatures generated by blockchain users are defined. Additionally, scenarios that generate and use duplicated signatures are applied in an actual bitcoin environment to demonstrate that actual bitcoin users' private keys can be recovered.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2013년도 추계학술발표대회
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• pp.400-401
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• 2013

Mobility in a network causes link disconnections and link recovery is vital for reliability of a network. A link failure affects all the preceding nodes on a damaged routing path; creates communication delay, throughput degradation, and congestion. This paper proposes link recovery mechanisms in CCN based networks. Packet overhearing is used to update neighboring nodes information. The recovery is done by forwarding node resulting in low control overhead, and better efficiency. The proposed mechanisms increase overall performance of a typical CCN and simulation results show that our proposed scheme works very well in densely populated networks with high mobility.

• 한국정보전자통신기술학회논문지
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• 제12권2호
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• pp.155-161
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• 2019

오늘날 수많은 기업과 기관들은 인터넷을 사용한 서비스를 제공하고 있으며, 이를 효율적이고 안정적으로 관리할 수 있도록 정보시스템을 구축하고 운영한다. 정보시스템은 재해 또는 장애로 인해 정상적인 서비스를 제공 할 수 있는 기능을 손실할 가능성을 내포하고 있다. 이에 재해복구시스템을 활용하여 이를 대비하고 있다. 그러나 기존의 재해 복구시스템은 시스템 복구를 위한 파일이 손상되는 경우 정상적으로 복구를 수행할 수 없다. 이에 본 논문에서는 하이퍼레저 패브릭 블록체인을 활용하여 시스템 복구 파일의 무결성을 검증하고 복구를 진행할 수 있는 시스템을 제안한다. 블록생성을 위하여 PBFT 합의 알고리즘을 사용하며, 블록체인 네트워크의 리더 노드에 의해 수행된다. 장애 상황 발생 시 복구 대상의 복구 파일의 해시 값을 블록체인 내의 해시 값과 비교하는 검증 작업을 거쳐 복구 파일의 무결성을 확인하고 복구를 진행한다. 제안 기법의 평가를 위하여 기존의 시스템 복구기법과 데이터 정합성, 데이터 보존 여부, 복구 파일 무결성 검증, 제안 기법 사용 시 트래픽 발생량을 분석하여 실제 적용 가능 여부를 확인하였다.

• Journal of Information Technology Applications and Management
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• 제23권4호
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• pp.25-39
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• 2016

Asset prices decline sharply and stock markets collapse when financial crisis happens. Recently we have encountered more frequent financial crises than ever. 1998 currency crisis and 2008 global financial crisis triggered academic researches on early warning systems that aim to detect the symptom of financial crisis in advance. This study proposes a risk recovery index for detection of good opportunities from financial market instability. We use SVM classifier algorithms to separate recovery period from unstable financial market data. Input variables are KOSPI index and V-KOSPI200 index. Our SVM algorithms show highly accurate forecasting results on testing data as well as training data. Risk recovery index is derived from our SVM-trained outputs. We develop a trading system that utilizes the suggested risk recovery index. The trading result records very high profit, that is, its annual return runs to 121%.

• International journal of advanced smart convergence
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• 제1권2호
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• pp.26-29
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• 2012

Recently, to efficiently support the real-time requirements of RTLS( Real Time Location System) services, interest in the main memory DBMS is rising. In the main memory DBMS, because all data can be lost when the system failure happens, the recovery method is very important for the stability of the database. Especially, disk I/O in executing the log and the checkpoint becomes the bottleneck of letting down the total system performance. Therefore, it is urgently necessary to research about the recovery method to reduce disk I/O in the main memory DBMS. Therefore, In this paper, we analyzed existing log techniques and check point techniques and existing main memory DBMSs' recovery techniques for recovery techniques research for main memory DBMS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제2권2호
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• pp.82-102
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• 2008

Packet losses tend to occur during short error bursts separated by long periods of relatively error-free transmission. There is also a significant spatial correlation in loss among the receiver nodes in a multicast session. To recover packet transmission errors at the transport layer, tree-based protocols construct a logical tree for error recovery before data transmission is started. The current tree construction scheme does not scale well because it overloads the sender node. We propose a scalable recovery tree construction scheme considering these properties. Unlike the existing tree construction schemes, our scheme distributes some tasks normally handled by the sender node to specific nodes acting as repair node distributors. It also allows receiver nodes to adaptively re-select their repair node when they experience unacceptable error recovery delay. Simulation results show that our scheme constructs the logical tree with reduced message and time overhead. Our analysis also indicates that it provides fast error recovery, since it can reduce the number of additional retransmissions from its upstream repair nodes or sender node.

• Journal of the Korean Data and Information Science Society
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• 제19권4호
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• pp.1123-1131
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• 2008

A considerable amount of research has focused on the dimensionality of service failure and recovery construct. This paper is focused on service failure and recovery in the Korean native cattle and imported beef restaurant industry in the Korea. So, this paper has adapted Kau and Loh's Service recovery measurement scale so that restaurant managers can use it to determine how customers perceive the service quality in Korean native cattle beef restaurant and imported beef restaurant. The purpose of this research is to test the difference in pre-purchase expectation and post-purchase actual performance of 4 dimensions between the restaurants that sell the beef of Korean native cattle and imported cattle. The paired t -test is used to test difference of pre-purchase expectation and post-purchase actual performance for service recovery measurement scale's 4 dimensions of the 2 restaurant types. But, there is significant difference between pre-purchase expectation and post-purchase actual performance in the 2 restaurant types.