• Journal of Internet of Things and Convergence
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• v.10 no.6
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• pp.111-116
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• 2024

The core of blockchain technology lies in the fact that instead of a centralized approach, individual nodes autonomously create blocks, but go through a consensus process so that eventually, all nodes have the same blockchain ledger. The technology used in this process is the consensus algorithm. Additionally, the consensus algorithm also helps solve the issue of double spending. To address this, the consensus algorithms used, such as Proof of Work (PoW), Proof of Stake (PoS), and Delegated Proof of Stake (DPoS), have been examined. Therefore, this paper aims to examine the types of double-spending attacks in blockchain and propose a Delegated Proof of Stake (DPoS) consensus algorithm incorporating Counting Bloom Filters (CBF) to prevent double-spending attacks and collusion among delegates.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.1-10
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• 2021

The purpose of the study is to contribute to the positive development of blockchain technology by providing data to examine security vulnerabilities and threats to blockchain-based services and review countermeasures. The findings of this study are as follows. Threats to the security of blockchain-based services can be classified into application security threats, smart contract security threats, and network (P2P) security threats. First, application security threats include wallet theft (e-wallet stealing), double spending (double payment attack), and cryptojacking (mining malware infection). Second, smart contract security threats are divided into reentrancy attacks, replay attacks, and balance increasing attacks. Third, network (P2P) security threats are divided into the 51% control attack, Sybil attack, balance attack, eclipse attack (spread false information attack), selfish mining (selfish mining monopoly), block withholding attack, DDoS attack (distributed service denial attack) and DNS/BGP hijacks. Through this study, it is possible to discuss the future plans of the blockchain technology-based ecosystem through understanding the functional characteristics of transparency or some privacy that can be obtained within the blockchain. It also supports effective coping with various security threats.

• Journal of the Korea Convergence Society
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• v.9 no.9
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• pp.83-88
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• 2018

The blockchain is the technique which is used in decentralized system instead of centralized system. Its characteristics are anonymous and transparency. However, there are still some traditional attacks. In this paper, we introduced some of the famous consensus algorithm with blockchain: Bitcoin, Algorand, and IOTA. Also, this paper talked about how each consensus algorithm tried to solve those traditional attacks such as double spending attack or sybil attack. Furthermore, if the consensus algorithm does not consider those attacks yet, then the author would introduce additional methods to solve those attacks. Furthermore, this paper proposed the new scenario that can make classical attacks be happened.