• Journal of the Korea Society of Computer and Information
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• v.26 no.4
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• pp.75-84
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• 2021

In this paper, we introduce InfoDID, a robust user information management service based on DID that manages user information reliably. Since blockchain technology provides an environment in which data can be handled transparently on a decentralized basis, various services using blockchain are currently being developed As the importance of user's personal information has recently emerged, the DID technology is receiving attention. The technology allows a user to control his or her information through decentralized identifiers, and various information management services are being tried based on the technology. Using blockchain-based DID technology, InfoDID reliably controls personal information requested frequently, helping users to provide their information to other services more conveniently. In addition, to support service continuity, InfoDID uses BR2K technique that provides robust execution of blockchain application services, so that even partial service failures can be systematically recovered. To facilitate this operation, we present a replication status monitoring tool that can continuously check the replication states of blockchain application services running in association with the BR2K technique such as InfoDID.

• Journal of Information Processing Systems
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• v.18 no.6
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• pp.763-769
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• 2022

Transportation allocation requires information such as storage location and order information. In order to guarantee the safe transmission and real-time sharing of information in all links, an intelligent transportation control system based on blockchain technology is designed. Firstly, the technical architecture of intelligent transportation information traceability blockchain and the overall architecture of intelligent transportation control system were designed. Secondly, the transportation management demand module and storage demand management module were designed, and the control process of each module was given. Then, the type of intelligent transportation vehicle was defined, the objective function of intelligent transportation control was designed, and the objective function of intelligent transportation control was constructed. Finally, the intelligent transportation control was realized by genetic algorithm. It was found that when the transportation order volume was 50×103, and the CPU occupancy of the designed system was only 11.8%. The reliability attenuation of the code deletion scheme was lower, indicating better performance of the designed system.

• Journal of Information Processing Systems
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• v.16 no.3
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• pp.699-717
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• 2020

Propagation time on permissionless blockchain plays a significant role in terms of stability and performance in the decentralized systems. A large number of activities are disseminated to the whole nodes in the decentralized peer-to-peer network, thus causing propagation delay. The stability of the system is our concern in the first place. The propagation delay opens up opportunities for attackers to apply their protocol. Either by accelerating or decelerating the propagation time directly without proper calculation, it brings numerous negative impacts to the entire blockchain system. In this paper, we thoroughly review and elaborate on several parameters related to the propagation time in such a system. We describe our findings in terms of data communication, transaction propagation, and the possibility of an interference attack that caused an extra propagation time. Furthermore, we present the influence of block size, consensus, and blockchain scalability, including the relation of parameters. In the last session, we remark several points associated with the propagation time and use cases to avoid dilemmas in the light of the experiments and literary works.

• Journal of the Korea Society of Computer and Information
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• v.28 no.3
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• pp.59-65
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• 2023

As research on blockchain applications in various fields is actively increasing, management of private keys that prove users of blockchain has become important. If you lose your private key, you lose all your data. In order to solve this problem, previously, blockchain wallets, private key recovery using partial information, and private key recovery through distributed storage have been proposed. In this paper, we propose a safe private key backup and recovery method using Shamir's Secrete Sharing (SSS) scheme and biometric information, and evaluate its safety. In this paper, we propose a safe private key backup and recovery method using Shamir's Secrete Sharing (SSS) scheme and biometric information, and evaluate its safety against robustness during message exchange, replay attack, man-in-the-middle attack and forgery and tampering attack.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.5
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• pp.1634-1652
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• 2022

Due to the increasing need for data sharing in the age of big data, how to achieve data access control and implement user permission revocation in the blockchain environment becomes an urgent problem. To solve the above problems, we propose a novel blockchain-based data sharing scheme (BDSS) with fine-grained access control and permission revocation in this paper, which regards the medical environment as the application scenario. In this scheme, we separate the public part and private part of the electronic medical record (EMR). Then, we use symmetric searchable encryption (SSE) technology to encrypt these two parts separately, and use attribute-based encryption (ABE) technology to encrypt symmetric keys which used in SSE technology separately. This guarantees better fine-grained access control and makes patients to share data at ease. In addition, we design a mechanism for EMR permission grant and revocation so that hospital can verify attribute set to determine whether to grant and revoke access permission through blockchain, so it is no longer necessary for ciphertext re-encryption and key update. Finally, security analysis, security proof and performance evaluation demonstrate that the proposed scheme is safe and effective in practical applications.

• Convergence Security Journal
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• v.20 no.2
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• pp.69-76
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• 2020

Blockchain 2.0 supports programmable smart contract for the various distributed application. However, the environment of running smart contract is limited in the blockchain, so the smart contract only get the deterministic information, such as block height, block hash, and so on. Therefore, some applications, which requires random information, such as lottery or batting, should use oracle service that supply the information outside of blockchain. This paper develops a random number generator oracle service. The random number generator oracle service use irregular big data as entropy source. This paper tests the randomness of bits sequence generated from oracle service using NIST SP800-22. This paper also describes the advantages of irregular big data in our model in perspective of cost comparing hardware entropy source.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.286-293
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• 2021

Smart contract based on the blockchain technology can be applied to the real estate registry including transactions. The Ethereum coin using multi layered protocol is widely accepted as the token for the smart contract. Block chain smart contract using SOLIDITY or PYTHON can mediate transactions auch as sale or lease, creating various scenarios in the property market. Those smart contract can construct the basis for the blockchain real estate registry, which is expected to overcome conventional transaction costs concerning the national law system, the asymmetric information and the currency exchange. The advantages of blockchain technology, namely security, decentralization, global transparency and openness can be applied to the smart contract system on the property registry. Several countries have advanced such blockchain real estate registry project recently, but no actual implementation has been reported for years, owing to institutional and technological impasses.

• International Journal of Computer Science & Network Security
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• v.24 no.3
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• pp.1-11
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• 2024

Payment systems are evolving, and this study examines how blockchain and AI improve online transactional security and service quality. The study examines micro and macro payment systems, compares online, and offline methods all over the world. The study also examines how blockchain and AI affect payment system security, privacy, and efficiency globally and rapidly digitizing economy. Digital payment methods are growing all over the world with high literacy and digital engagement, but they face challenges. The research highlights cybersecurity threats and the need to balance user convenience and security. It suggests blockchain and AI improve online payment services, supporting the policies for different countries. In this extensive research survey, we compare and evaluate the strengths and weaknesses of various payment systems, their practicality, and their robustness. This study also examines how technological innovations and payment systems interact to reveal how blockchain and AI could transform the financial sector. It seeks to understand how technology-enhancing service quality can boost customer satisfaction and financial stability in the digital age. The findings should help policymakers, financial institutions, and technology developers optimize online payment systems for a more secure and efficient digital economy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.9
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• pp.3693-3711
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• 2020

e-Governance is a medium to offer various services to citizens through a web portal, that exists in many countries nowadays. The existing e-Governance technology is a vast, centrally managed database and a set of applications that connect to it via web interfaces. Despite the modernisation of services, it remains with the lack of transparency. Thus, the existing infrastructure of e-Governance paves the way for corrupt practises by the bureaucrats. e-Governance needs a powerful underlying technology which doesn't provide any way to allow tampering of the record and which in turn eliminates corruption. In this paper, we took land registration as a use-case for building e-Governance by keeping Blockchain as an underlying technology, to put off the corrupt practices and to bring transparency. Once transactions in land registration added to the Blockchain, it is immutable as it is cryptographically secured. Besides, the blockchain technology is secured as the ledger is distributed over the network. If a hacker wants to modify the ledger, he needs to hack every node in the blockchain network. Hyperledger Fabric, a permissioned Blockchain adopted for implementation and Hyperledger Caliper for performance analysis with these evaluation metrics such as throughput, latency and execution time.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.5
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• pp.899-914
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• 2022

A blockchain-based decentralized service can offer reliable services without the centralized server by operating the system based on the consensus among byzantine participants. Participants can interact with the blockchain network through a digital signature mechanism but the private key management issue remains unresolved. NIST SP800-57 provides a key-management guidance but this guidance is not appropriate for blockchain-based services because it does not consider a decentralized environment. In this paper, we define the core functions of the blockchain wallet application for private key management and present security protections according to NIST SP800-57, as well as related techniques to satisfy them. Finally, we propose the private key management guideline for secure blockchain-based decentralized services.