• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.7
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• pp.2286-2304
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• 2022

Blockchain is a distributed ledger that combines technologies such as cryptography, consensus mechanism, peer-to-peer transmission, and time stamping. The rapid development of blockchain has attracted attention from all walks of life, but storage scalability issues have hindered the application of blockchain. In this paper, a scalable blockchain storage model based on Distributed Hash Table (DHT) and the InterPlanetary File System (IPFS) was proposed. This paper introduces the current research status of the scalable blockchain storage model, as well as the basic principles of DHT and the InterPlanetary File System. The model construction and workflow are explained in detail. At the same time, the DHT network construction mechanism, block heat identification mechanism, new node initialization mechanism, and block data read and write mechanism in the model are described in detail. Experimental results show that this model can reduce the storage burden of nodes, and at the same time, the blockchain network can accommodate more local blocks under the same block height.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06a
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• pp.292-294
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• 2006

최근 수년간 클라이언트 모델에서 발생하는 문제인 서버 병목 현상, Dos공격, 그리고 시스템의 확장성에 따른 비용 증가 등의 문제를 해결하는 방법으로 P2P 방식이 활발히 연구되고 있으며, 그 중 사용자간 파일 공유하는 분야에 적용된 P2P가 가장 널리 알려져 있다. 본 논문에서는 플랫폼에 독립적이고, 네트워크 디바이스에 독립적인 환경을 지원하는 JXTA 네트워크 환경에서 분산된 자원의 효율적인 검색을 하는 DHT(Distributed Hash Table) 알고리즘을 제안하고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.982-985
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• 2007

인터넷의 보급과 PC의 발달로 정보의 분산과 공유가 가속화를 이루었고, 컴퓨팅 구조가 인터넷 기반으로 변화하였다. 이후 지금까지 수많은 시스템들이 클라이언트/서버 모델을 유지하고 있는 한편 대단위 분산 다중서버로 구성되는 환경이 출현하였다. 클라이언트/서버 모델에서 사용자들의 정보 공유의 제약을 해소하기 위해 개인의 피어 사이에 서로 공유하는 P2P(Peer-to-Peer) 패러다임이 출현 되었다. 하지만 기존의 DHT(Distributed Hash Table)를 기반으로 하는 P2P 시스템에선 정보를 검색할 때, 검색어와 검색결과의 모호성이 존재하고, 범위 검색을 지원하지 못하는 문제가 있었다. 우리는 이 문제를 해결할 한 가지 방안을 본 논문에서 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.46-48
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• 2004

Distributed Hash Table(DHT)를 기반으로 하는 structured P2P에서 복잡 질의를 통친 원하는 자료를 찾는 것은 쉽지 않다. 이와 같은 것들 중 하나가 범위 값을 이용하여 원하는 값을 찾는 range query이다. 본 논문에서는 full binary tree의 특징을 이용하여 structured P2P에서 range query를 수행할 수 있는 mapping 함수와, load balance를 지원하기 위한 방법을 제안한다 또한 실험을 통해서 이 방법들이 어느 정도의 성능을 보여주는 지도 살펴본다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.11
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• pp.1-11
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• 2009

A content based pub/sub (Publish/subscribe) services at the peer-to-peer network has the requirements about how to distribute contents information of subscriber and to delivery the events efficiently. For satisfying the requirements, a DHT(Distributed Hash Table) based pub/sub overlay networking and tree type topology based network construction using filter technique have been proposed. The DHT based technique is suitable for topic based pub/sub service but it's not good contents based service that has the variable requirements. And also filter based tree topology networking is not efficient at the environment where the user requirements are distributed. In this paper we propose the R-Tree algorithm based pub/sub overlay network construction method. The proposed scheme provides cost effective event delivery method by mapping user requirement to multi-dimension and hierarchical grouping of the requirements. It is verified by simulation at the variable environment of user requirements and events.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.550-552
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• 2004

분산 해시 테이블 (Distributed Hash Table) 을 사용한 P2P 시스템에서는 해시함수를 사용하며 파일과 노드의 ID를 정의하고 파일의 ID와 매핑 (mapping) 되는 ID를 가진 노드에 파일을 저장함으로써 시스템 전체에 파일을 완전히 분산시킨다. 이러한 시스템에서는 파일을 찾을 때 해시된 파일 ID로 찾기 때문에 정확한 매치 (exact match) 만 가능하다. 하지만 현재 P2P 파일 공유 시스템에서는 파일의 전체 이름을 정확히 알지 못하더라도 부분적인 키워드로 파일을 검색할 수 있도록 하는 키워드 검색 (keyword search) 이 요구된다. 본 논문에서는 분산 해시 테이블을 기반으로 하는 P2P 시스템에서 키워드 검색이 가능하도록 하는 방안을 제안한다.

• Journal of the Korea Society of Computer and Information
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• v.16 no.3
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• pp.131-140
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• 2011

File pollution (i.e., sharing of corrupted files, or contaminating index information with bogus index records) is a de facto problem in many file sharing Peer-to-Peer (P2P) systems in use today. Since pollution squanders network resources and frustrates users with unprofitable downloads (due to corrupted files) and unproductive download trials (due to bogus index records), the viability of P2P systems (and similar distributed information-sharing applications) is questionable unless properly addressed. Thus, developing effective anti-pollution mechanisms is an immediate problem in this literature. This paper provides useful information and deep insight with future researchers who want to design an effective anti-pollution mechanism throughout an extensive measurement study of user behavior and file pollution in a representative DHT-based P2P system, the Kad network.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.10
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• pp.752-760
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• 2009

Emerging peer-to-peer systems benefit from the large amount of resources provided by many peers. However, many peer-to-peer systems or applications suffer from malicious peers and it is not guaranteed that peers are always online. Micropayment systems are accounting and charging mechanism for buying services, so we can apply them to solve these problems. In the past the majority of micropayment system uses a centralized broker but the problem with most existing micropayment system is a heavy load on the broker. For instance, when an owner of the coin is offline, the broker delegates the owner and handles payment messages. It occurs frequently because of characteristic of peer-to-peer system and is another load of the broker. In this paper we introduce DPay, a peer-to-peer micropayment system that uses distributed hash table (DHT) for storing encrypted payment messages and increases scalability and reduces the load of broker by removing downtime protocol. We show the idea of real-time double spending detection in DPay and report the results of several evaluations in order to compare DPay and other payment scheme. In simulation result, the load of broker in DPay is reduced by 30% on average of other previous payment scheme. We expect that DPay can apply various peer-to-peer systems because it provides a real-time double spending detection and stores more secure payment messages.

• Journal of Information Processing Systems
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• v.10 no.4
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• pp.628-645
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• 2014

In past few years, distributed hash table (DHT)-based P2P systems have been proven to be a promising way to manage decentralized index information and provide efficient lookup services. However, the skewness of users' preferences regarding keywords contained in a multi-keyword query causes a query load imbalance that combines both routing and response load. This imbalance means long file retrieval latency that negatively influences the overall system performance. Although index replication has a great potential for alleviating this problem, existing schemes did not explicitly address it or incurred high cost. To overcome this issue, we propose, in this paper, an integrated solution that consists of three replication schemes to alleviate query load imbalance while minimizing the cost. The first scheme is an active index replication that is used in order to decrease routing load in the system and to distribute response load of an index among peers that store replicas of the index. The second scheme is a proactive pointer replication that places location information of each index to a predetermined number of peers for reducing maintenance cost between the index and its replicas. The third scheme is a passive index replication that guarantees the maximum query load of peers. The result of simulations indicates that the proposed schemes can help alleviate the query load imbalance of peers. Moreover, it was found by comparison that our schemes are more cost-effective on placing replicas than PCache and EAD.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.10 no.4
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• pp.121-127
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• 2011

Many peer-to-peer (p2p) systems have been studied in distributed, ubiquitous computing environments. Distributed hash table (DHT)-based p2p systems can improve load-balancing even though locality utilization and user mobility are not guaranteed. We propose a mobile locality-based hierarchical p2p overlay network (MLH-Net) to address locality problems without any other services. MLH-Net utilizes mobility features in a mobile environment. MLH-Net is constructed as two layers, an upper layer formed with super-nodes and a lower layer formed with normal-nodes. Because super-nodes can share advertisements, we can guarantee physical locality utilization between a requestor and a target during any discovery process. To overcome a node failure, we propose a simple recovery mechanism. The simulation results demonstrate that MLH-Net can decrease discovery routing hops by 15% compared with JXTA and 66% compared with Chord.