• ETRI Journal
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• 제33권5호
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• pp.826-829
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• 2011

Distributed systems particularly suffer from Sybil attacks, where a malicious user creates numerous bogus nodes to influence the functions of the system. In this letter, we propose a Bloom filter-based scheme, SybilBF, to fight against Sybil attacks. A Bloom filter presents a set of Sybil nodes according to historical behavior, which can be disseminated to at least n (e-1)/e honest nodes. Our evaluation shows that SybilBF outperforms state of the art mechanisms improving SybilLimit by a factor of (1/e)${\gamma}$ at least.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권6호
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• pp.1311-1326
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• 2010

Peer-to-peer (P2P) networks consume the most bandwidth in the current Internet and file sharing accounts for the majority of the P2P traffic. Thus it is important for a P2P file sharing application to be efficient in bandwidth consumption. Bandwidth consumption as much as downloaded file sizes is inevitable, but those in file search and bad downloads, e.g. wrong, corrupted, or malicious file downloads, are overheads. In this paper, we target to reduce these overheads even in the presence of high volume of malicious users and their bad files. Sybil attacks are the example of such hostile environment. Sybil attacker creates a large number of identities (Sybil nodes) and unfairly influences the system. When a large portion of the system is subverted, either in terms of the number of users or the number of files shared in the system, the overheads due to the bad downloads rapidly increase. We propose ELiSyR, a file search protocol that can tolerate such a hostile environment. ELiSyR uses social networks for P2P file search and finds benign files in 71% of searches even when more than half of the users are malicious. Furthermore, ELiSyR provides similar success with less bandwidth than other general efforts against Sybil attacks. We compare our algorithm to SybilGuard, SybilLimit and EigenTrust in terms of bandwidth consumption and the likelihood of bad downloads. Our algorithm shows lower bandwidth consumption, similar chances of bad downloads and fairer distribution of computation loads than these general efforts. In return, our algorithm takes more rounds of search than them. However the time required for search is usually much less than the time required for downloads, so the delay in search is justifiable compared to the cost of bad downloads and subsequent re-search and downloads.

• Journal of Information Processing Systems
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• 제14권6호
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• pp.1431-1437
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• 2018

Securing objects in the Internet of Things (IoT) is essential. Authentication model is one candidate to secure an object, but it is only limited to handle a specific type of attack such as Sybil attack. The authentication model cannot handle other types of attack such as trust-based attacks. This paper proposed two-phase security protection for objects in IoT. The proposed method combined authentication and statistical models. The results showed that the proposed method could handle other attacks in addition to Sybil attacks, such as bad-mouthing attack, good-mouthing attack, and ballot stuffing attack.

• 전기전자학회논문지
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• 제23권2호
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• pp.413-418
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• 2019

기존의 센서 네트워크 상의 공격에는 Sniffing(도청) 공격, Flood 공격, Spoofing(위조)공격 등이 있고, 이에 대한 기본적인 대응 방법에는 암호화 및 인증 방법, 스위칭 방법 등이 있다. 무선 센서 네트워크(WSN)에서 네트워크 계층에서의 공격에는 Wormhole 공격, HELLO Flood 공격, Sybil 공격, 싱크홀 공격, 선택적 전달 공격 등이 있다. 이러한 공격들은 앞서 말한 기본적인 대응방안으로 방어 되지 않는 경우가 있다. 이러한 공격들에 대한 새로운 대응방안에는 정기적인 키 변경, 정기적인 네트워크 모니터링 등의 여러 가지 방안들이 있다. 본 논문에서는 무선 센서 네트워크의 네트워크 계층의 여러 가지 위협(공격)들과 그에 따른 새로운 대응방안들에 대해 제시한다.

• 한국융합학회논문지
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• 제9권9호
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• pp.83-88
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• 2018

블록체인은 중앙 집중화된 시스템이 아닌 분산화 된 시스템을 구현하는 데에 사용되는 기술로써, 익명성, 투명성 등을 특징으로 한다. 그러나 아직 블록체인을 상용화하기에는 고질적인 공격들이 존재한다. 본 논문에서는 이러한 블록체인을 구현하기 위해서 존재하는 대표적인 합의 알고리즘으로써 Bitcoin, Algorand, 그리고 IOTA를 소개하고, 각각의 합의 알고리즘들이 어떠한 방법으로 블록체인의 고질적인 공격들인 이중 지불 공격이나 시빌 공격을 해결하는지, 혹은 해결하지 못하고 있다면 어떤 방법으로 해결할 수 있는지를 소개한다. 뿐만 아니라 기존의 고질적인 공격이 가능한 새로운 시나리오를 제안한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권12호
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• pp.6214-6242
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• 2019

Routing in mobile ad hoc networks is performed in a distributed fashion where each node acts as host and router, such that it forwards incoming packets for others without relying on a dedicated router. Nodes are mostly resource constraint and the users are usually inclined to conserve their resources and exhibit selfish behaviour by not contributing in the routing process. The trust and reputation models have been proposed to motivate selfish nodes for cooperation in the packet forwarding process. Nodes having bad trust or reputation are detected and secluded from the network, eventually. However, due to the lack of proper identity management and use of non-persistent identities in ad hoc networks, malicious nodes can pose various threats to these methods. For example, a malicious node can discard the bad reputed identity and enter into the system with another identity afresh, called whitewashing. Similarly, a malicious node may create more than one identity, called Sybil attack, for self-promotion, defame other nodes, and broadcast fake recommendations in the network. These identity-based attacks disrupt the overall detection of the reputation systems. In this paper, we propose a reputation-based scheme that detects selfish nodes and deters identity attacks. We address the issue in such a way that, for normal selfish nodes, it will become no longer advantageous to carry out a whitewash. Sybil attackers are also discouraged (i.e., on a single battery, they may create fewer identities). We design and analyse our rationale via game theory and evaluate our proposed reputation system using NS-2 simulator. The results obtained from the simulation demonstrate that our proposed technique considerably diminishes the throughput and utility of selfish nodes with a single identity and selfish nodes with multiple identities when compared to the benchmark scheme.

• Journal of Communications and Networks
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• 제17권2호
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• pp.145-156
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• 2015

In recent years, electronic commerce and online social networks (OSNs) have experienced fast growth, and as a result, recommendation systems (RSs) have become extremely common. Accuracy and robustness are important performance indexes that characterize customized information or suggestions provided by RSs. However, nefarious users may be present, and they can distort information within the RSs by creating fake identities (Sybils). Although prior research has attempted to mitigate the negative impact of Sybils, the presence of these fake identities remains an unsolved problem. In this paper, we introduce a new weighted link analysis and influence level for RSs resistant to Sybil attacks. Our approach is validated through simulations of a broad range of attacks, and it is found to outperform other state-of-the-art recommendation methods in terms of both accuracy and robustness.

• International Journal of Computer Science & Network Security
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• 제21권6호
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• pp.294-303
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• 2021

VANET is an upcoming technology with an encouraging prospect as well as great challenges, specifically in its security. This paper intends to survey such probable attacks and the correlating detection mechanisms that are introduced in the literature. Accordingly, administering security and protecting the owner's privacy has become a primary argument in VANETs. To furnish stronger security and preserve privacy, one should recognize the various probable attacks on the network and the essence of their behavior. This paper presents a comprehensive survey on diversified attacks and the recommended unfolding by the various researchers which concentrate on security services and the corresponding countermeasures to make VANET communications more secure.

• 한국인터넷방송통신학회논문지
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• 제13권1호
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• pp.115-120
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• 2013

무선 센서 네트워크의 다양한 용도만큼 많은 취약점과 다양한 공격 가능성이 여러 논문에서 제기되고 있다. 여러 공격 중에서도 시빌(sybil) 공격은 공격 노드가 많은 수의 거짓 노드를 생성하여 네트워크에 잘 못된 정보를 보내는 공격이다. 사용자가 공격을 받았음을 인지하지 못하고 거짓 노드로부터 온 데이터를 사실로 오인하고 사용하게 되면 민감한 데이터일 경우 재앙이 될 수도 있다. 인증과 같은 암호화 기법으로 방어를 할 수 있지만 저전력, 저사양을 특징으로 하는 센서 노드에서는 구현이 곤란하다. 본 논문에서는 센서 네트워크에서 시빌 공격으로 생성된 거짓 노드를 탐지하는 기법을 제안한다. 제안 기법은 정상 노드의 군집과 거짓 노드의 군집 간에 네트워크가 약하다는 특징을 이용한다. 또한 센서 노드의 저전력을 고려하여 기존 에너지 고려 라우팅에 약간의 데이터를 추가함으로써 오버헤드를 최소화 하였다. 실험 결과를 통해 제안 기법이 기존 에너지 고려 라우팅에 비해 추가적인 에너지 소모가 극히 적으면서도 시빌 공격의 탐지를 90% 이상 할 수 있음을 보였다.

• International Journal of Internet, Broadcasting and Communication
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• 제13권4호
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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.