• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.4
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• pp.987-997
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• 2018

Blockchain has tamper-free, so many applications are developing to leverage tamper-free features of blockchain. MIT Media Labs proposed BlockCerts, educational certificate blockchain System, to solve problems of legacy certificate verifications. Existing educational certificate blockchain Systems are based on public blockchain such as bitcoin, Ethereum, so any entity can participate educational institute in principal. Moreover, the exisitng educational certricate blockchain system utilizes the integrity of blockchain, but the confidentiality of the educational certificate is not provided. This paper propose a digital certificate system based on private blockchain, name HyperCerts. Therefore, only trusted entity can participate in the private blockchain network, Hyperledger, as the issuer of digital certificate. Furthermore, the practical byzantine fault tolerance is used as consensus algorithm, HyperCerts reduce dramatically the latency of issuing digital certificate and required computing power. HyperCerts stores the hash value of digital certificate into the ledger, so breach of personal information by malicious entity in the private blockchain is protected.

• KNOM Review
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• v.21 no.2
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• pp.18-25
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• 2018

Since the development of block-chain technology by Satoshi Nakamoto and Bitcoin pioneered a new cryptocurrency market, a number of scale of cryptocurrency have emerged. There are crimes taking place using the anonymity and vulnerabilities of block-chain technology, and many studies are underway to improve vulnerability and prevent crime. However, they are not enough to detect users who commit crimes. Therefore, it is very important to detect abnormal behavior such as money laundering and stealing cryptocurrency from the network. In this paper, the characteristics of the transactions and user graphs in the Bitcoin network are collected and statistical information is extracted from them and presented as plots on the log scale. Finally, we analyze visualized plots according to the Densification Power Law and Power Law Degree, as a result, present features appropriate for detection of anomalies involving abnormal transactions and abnormal users in the Bitcoin network.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.509-517
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• 2020

This study examined Sino-globalization through the network analysis of Chinese immigrants, international students, and travelers. The data were collected from the United Nations for immigrants, UNESCO for international students, and Ministry of Culture and Tourism of China for travelers. Consequently, Chinese immigrants and international students' favorite destinations were advanced Western countries, and Chinese travelers showed a high preference for Asian regions. Specifically, Thailand was the most popular destination for traveling, while the U.S. appeared to be the main destination for Chinese immigrants and students. The QAP analysis results showed a statistically significant correlation between the immigrant network and international student network. MR-QAP analysis found a causal relationship between the two networks. These findings may serve as empirical evidence for the Chinese government to review potential opportunities and problems related to Sino-globalization and provide the basis for preparing policy measures for other countries. Subsequent studies should compensate for research limitations by analyzing specific factors affecting national choice of Chinese immigrants, students, and travelers. The economic, social, and cultural impacts of China's globalization on other countries need to be discussed using qualitative research.