peer to peer network
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2022 ◽  
pp. 16-27
Author(s):  
Mohammad Khalid Imam Rahmani

Blockchain is a distributed decentralized peer-to-peer network aiming to facilitate the immutability and security of data. Towards the service orientation, blockchain is a collection of distributed blocks having unique hash codes without any point of failure. Each block is stored on distributed ledgers, and transactions with them are secure, transparent, immutable, and traceable. To create a new block and allow a transaction to complete, an agreement between all parties is required. To reach an agreement in a blockchain network, consensus algorithms are used. In this chapter, fundamental principles and algorithms of blockchain networks have been discussed, and a detailed review of the blockchain consensus algorithms PoW, PoS, DPoS, PoET, PoWeight, PoB, PoA, and PoC have been provided including the merits and demerits of consensus algorithms with analysis to provide a deep understanding of the current research trends and future challenges.


2021 ◽  
Author(s):  
Ngoc Hong Tran ◽  
Tri Nguyen ◽  
Quoc Binh Nguyen ◽  
Susanna Pirttikangas ◽  
M-Tahar Kechadi

This paper investigates the situation in which exists the unshared Internet in specific areas while users in there need instant advice from others nearby. Hence, a peer-to-peer network is necessary and established by connecting all neighbouring mobile devices so that they can exchange questions and recommendations. However, not all received recommendations are reliable as users may be unknown to each other. Therefore, the trustworthiness of advice is evaluated based on the advisor's reputation score. The reputation score is locally stored in the user’s mobile device. It is not completely guaranteed that the reputation score is trustful if its owner uses it for a wrong intention. In addition, another privacy problem is about honestly auditing the reputation score on the advising user by the questioning user. Therefore, this work proposes a security model, namely Crystal, for securely managing distributed reputation scores and for preserving user privacy. Crystal ensures that the reputation score can be verified, computed and audited in a secret way. Another significant point is that the device in the peer-to-peer network has limits in physical resources such as bandwidth, power and memory. For this issue, Crystal applies lightweight Elliptic Curve Cryptographic algorithms so that Crystal consumes less the physical resources of devices. The experimental results prove that our proposed model performance is promising.


2021 ◽  
Author(s):  
Logi Karlsson ◽  
Astrid Kemperman ◽  
Sara Dolnicar

Demand for tourist accommodation offered on peer-to-peer networks is skyrocketing. In such networks tourists can only book if the accommodation provider (host) gives their permission. Needing permission to book accommodation is radically new in tourism. No hotel, motel or B&B assesses a booking inquiry in detail before accepting their booking. But do peer-to-peer network hosts actually refuse permission to book and, if so, why? A choice experiment with Airbnb hosts shows that refusing permission to book is common and that specific attributes of the booking inquiry—such as the purpose of their trip—affect the likelihood of getting permission to book.


2021 ◽  
Vol Volume 17, Issue 4 ◽  
Author(s):  
Massimo Bartoletti ◽  
Letterio Galletta ◽  
Maurizio Murgia

Decentralized blockchain platforms have enabled the secure exchange of crypto-assets without the intermediation of trusted authorities. To this purpose, these platforms rely on a peer-to-peer network of byzantine nodes, which collaboratively maintain an append-only ledger of transactions, called blockchain. Transactions represent the actions required by users, e.g. the transfer of some units of crypto-currency to another user, or the execution of a smart contract which distributes crypto-assets according to its internal logic. Part of the nodes of the peer-to-peer network compete to append transactions to the blockchain. To do so, they group the transactions sent by users into blocks, and update their view of the blockchain state by executing these transactions in the chosen order. Once a block of transactions is appended to the blockchain, the other nodes validate it, re-executing the transactions in the same order. The serial execution of transactions does not take advantage of the multi-core architecture of modern processors, so contributing to limit the throughput. In this paper we develop a theory of transaction parallelism for blockchains, which is based on static analysis of transactions and smart contracts. We illustrate how blockchain nodes can use our theory to parallelize the execution of transactions. Initial experiments on Ethereum show that our technique can improve the performance of nodes.


Mobile ad hoc networks as an infrastructure free, and constrained resource environment network. The network aim is to establish internet connectivity everywhere regardless of location. The applications of network are healthcare, disaster relief and military, where reliable communication is major concern. Communication in the network is initiated by establishing the communication route between source and destination and sending the information through it. One of the characteristics of MANETs is a peer-to-peer network, where intermediate nodes have to cooperate for reliable communication by acting as routers. In literature number of routing protocols have been designed based on the MANET’s peer to peer characteristic. However, it may not be every time true that the intermediate nodes act as faithful routers, and they may untrustworthy either due to malicious behavior or bottleneck. Number of secure protocols have been designed to mitigate malicious behavior by neglecting the bottleneck. The paper aims to define the bottleneck, and its importance in communication. Finally, how bottleneck influence on the MANETs performance during malicious nodes mitigation


Author(s):  
Federico Franzoni ◽  
Xavier Salleras ◽  
Vanesa Daza

AbstractOver the past decade, the Bitcoin P2P network protocol has become a reference model for all modern cryptocurrencies. While nodes in this network are known, the connections among them are kept hidden, as it is commonly believed that this helps protect from deanonymization and low-level attacks. However, adversaries can bypass this limitation by inferring connections through side channels. At the same time, the lack of topology information hinders the analysis of the network, which is essential to improve efficiency and security. In this paper, we thoroughly review network-level attacks and empirically show that topology obfuscation is not an effective countermeasure. We then argue that the benefits of an open topology potentially outweigh its risks, and propose a protocol to reliably infer and monitor connections among reachable nodes of the Bitcoin network. We formally analyze our protocol and experimentally evaluate its accuracy in both trusted and untrusted settings. Results show our system has a low impact on the network, and has precision and recall are over 90% with up to 20% of malicious nodes in the network.


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