Fair Exchange Mechanism for P2P Systems

2010 ◽  
Author(s):  
Xu Xiao-long ◽  
Xiong Jing-Yi ◽  
Cheng Chun-Ling
Keyword(s):  
Exchange Mechanism ◽  
Fair Exchange ◽  
P2p Systems

scholarly journals Secure and Efficient Key Exchange Mechanism for Heterogeneous Connected Objects

2021 ◽  
Author(s):  
Sofiane Aissani ◽  
Tarek Fettioune ◽  
Nafaa Maizia ◽  
Mohamed Mohammedi ◽  
Mawloud Omar
Keyword(s):  
Key Exchange ◽  
Exchange Mechanism

scholarly journals Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks

2021 ◽  
Vol 21 (2) ◽  
pp. 1-27
Author(s):  
Michał Król ◽  
Alberto Sonnino ◽  
Mustafa Al-Bassam ◽  
Argyrios G. Tasiopoulos ◽  
Etienne Rivière ◽  
...  
Keyword(s):  
Mobile Application ◽  
Reward System ◽  
Fair Exchange ◽  
Content Dissemination ◽  
Collusion Attacks ◽  
Computational Overhead ◽  
Smart Contract ◽  
Memory Footprint ◽  
Vast Range ◽  
Over Time

As cryptographic tokens and altcoins are increasingly being built to serve as utility tokens, the notion of useful work consensus protocols is becoming ever more important. With useful work consensus protocols, users get rewards after they have carried out some specific tasks useful for the network. While in some cases the proof of some utility or service can be provided, the majority of tasks are impossible to verify reliably. To deal with such cases, we design “Proof-of-Prestige” (PoP)—a reward system that can run directly on Proof-of-Stake (PoS) blockchains or as a smart contract on top of Proof-of-Work (PoW) blockchains. PoP introduces “prestige,” which is a volatile resource that, in contrast to coins, regenerates over time. Prestige can be gained by performing useful work, spent when benefiting from services, and directly translates to users minting power. Our scheme allows us to reliably reward decentralized workers while keeping the system free for the end-users. PoP is resistant against Sybil and collusion attacks and can be used with a vast range of unverifiable tasks. We build a simulator to assess the cryptoeconomic behavior of the system and deploy a full prototype of a content dissemination platform rewarding its participants. We implement the blockchain component on both Ethereum (PoW) and Cosmos (PoS), provide a mobile application, and connect it with our scheme with a negligible memory footprint. Finally, we adapt a fair exchange protocol allowing us to atomically exchange files for rewards also in scenarios where not all the parties have Internet connectivity. Our evaluation shows that even for large Ethereum traces, PoP introduces sub-millisecond computational overhead for miners in Cosmos and less than 0.013$ smart contract invocation cost for users in Ethereum.

Patients' Perceptions of Different Information Exchange Mechanisms: An Exploratory Study in the United States

2020 ◽  
Vol 59 (04/05) ◽  
pp. 162-178
Author(s):  
Pouyan Esmaeilzadeh
Keyword(s):  
United States ◽  
Health Care ◽  
Health Information ◽  
Health Care Providers ◽  
Information Exchange ◽  
The United States ◽  
Exchange Mechanism ◽  
Care Providers ◽  
Security Risks ◽  
Direct Exchange

Abstract Background Patients may seek health care services from various providers during treatment. These providers could serve in a network (affiliated) or practice separately (unaffiliated). Thus, using secure and reliable health information exchange (HIE) mechanisms would be critical to transfer sensitive personal health information (PHI) across distances. Studying patients' perceptions and opinions about exchange mechanisms could help health care providers build more complete HIEs' databases and develop robust privacy policies, consent processes, and patient education programs. Objectives Due to the exploratory nature of this study, we aim to shed more light on public perspectives (benefits, concerns, and risks) associated with the four data exchange practices in the health care sector. Methods In this study, we compared public perceptions and expectations regarding four common types of exchange mechanisms used in the United States (i.e., traditional, direct, query-based, patient-mediated exchange mechanisms). Traditional is an exchange through fax, paper mailing, or phone calls, direct is a provider-to-provider exchange, query-based is sharing patient data with a central repository, and patient-mediated is an exchange mechanism in which patients can access data and monitor sharing. Data were collected from 1,624 subjects using an online survey to examine the benefits, risks, and concerns associated with the four exchange mechanisms from patients' perspectives. Results Findings indicate that several concerns and risks such as privacy concerns, security risks, trust issues, and psychological risks are raised. Besides, multiple benefits such as access to complete information, communication improvement, timely and convenient information sharing, cost-saving, and medical error reduction are highlighted by respondents. Through consideration of all risks and benefits associated with the four exchange mechanisms, the direct HIE mechanism was selected by respondents as the most preferred mechanism of information exchange among providers. More than half of the respondents (56.18%) stated that overall they favored direct exchange over the other mechanisms. 42.70% of respondents expected to be more likely to share their PHI with health care providers who implemented and utilized a direct exchange mechanism. 43.26% of respondents believed that they would support health care providers to leverage a direct HIE mechanism for sharing their PHI with other providers. The results exhibit that individuals expect greater benefits and fewer adverse effects from direct HIE among health care providers. Overall, the general public sentiment is more in favor of direct data transfer. Our results highlight that greater public trust in exchange mechanisms is required, and information privacy and security risks must be addressed before the widespread implementation of such mechanisms. Conclusion This exploratory study's findings could be interesting for health care providers and HIE policymakers to analyze how consumers perceive the current exchange mechanisms, what concerns should be addressed, and how the exchange mechanisms could be modified to meet consumers' needs.

Effectiveness of Calcium Deficiency in Nanosized Hydroxyapatite for Removal of Fe(II), Cu(II), Ni(II) and Cr(VI) Ions from Aqueous Solutions

2019 ◽  
Vol 56 ◽  
pp. 17-27
Author(s):  
Van Dat Doan ◽  
Van Thuan Le ◽  
Hoang Sinh Le ◽  
Dinh Hien Ta ◽  
Hoai Thuong Nguyen
Keyword(s):  
Electron Microscopy ◽  
Ion Exchange ◽  
Aqueous Solutions ◽  
Calcium Deficiency ◽  
Exchange Mechanism ◽  
Precipitation Method ◽  
X Ray ◽  
Transmission Electron ◽  
Bet Method ◽  
Langmuir Isotherm Model

In this work, nanosized calcium deficient hydroxyapatite (nCDHA) was synthesized by the precipitation method, and then utilized as an adsorbent for removal of Fe (II), Cu (II), Ni (II) and Cr (VI) ions from aqueous solutions after characterizing it by various techniques as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and BET method. A possible structure of synthesized nCDHA was proposed. The adsorption study indicated that the adsorption equilibrium is well fitted with Langmuir isotherm model with the maximum adsorption capacities followed the order of Fe (II) > Cu (II) > Ni (II) > Cr (VI) with the values of 137.23, 128.02, 83.19 and 2.92 mg/g, respectively. The ion-exchange mechanism was dominant for the adsorption of metal ions onto nCDHA at initial metal concentrations lower than 0.01 mol/L. Along with the ion-exchange mechanism, there was an additional precipitation occurred on the surface of nCDHA in the case of Fe (II) and Cu (II) at initial concentrations higher than 0.01 mol/L.

Sodium-calcium exchange-mediated contractions in feline ventricular myocytes

1992 ◽  
Vol 263 (4) ◽  
pp. H1161-H1169 ◽  
Author(s):  
H. B. Nuss ◽  
S. R. Houser
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Ventricular Myocytes ◽  
Membrane Potentials ◽  
Exchange Mechanism ◽  
Ca Channel ◽  
Ca Current ◽  
Voltage Step ◽  
Reverse Mode ◽  
Sodium Calcium ◽  
Calcium Exchange

The hypothesis that Ca entry by the sarcolemmal Na-Ca exchange mechanism induces sarcoplasmic reticulum (SR) Ca release, loads the SR with Ca, and/or directly induces contractions by elevating cytosolic free Ca was tested in voltage-clamped feline ventricular myocytes. Intracellular Na concentration was increased by cellular dialysis to enhance Ca influx via "reverse-mode" Na-Ca exchange at positive membrane potentials, at which the "L-type" Ca current (ICa) should be small. Contractions were induced in the presence of Ca channel antagonists by depolarization to these potentials, suggesting that Ca influx via reverse-mode Na-Ca exchange was involved. These contractions had both phasic (SR related) and tonic components of shortening. They were smaller and began with more delay after depolarization than contractions which involved ICa. The magnitude of shortening was graded by the amount and duration of depolarization, suggesting that Ca influx via reverse-mode Na-Ca exchange has the capacity to induce and grade SR Ca release. Small slow contractions could be evoked in the presence of ryanodine (to impair SR function) and verapamil (to block ICa), supporting the idea that Ca influx via Na-Ca exchange is sufficient to directly activate the contractile proteins. Contractions induced by voltage steps to +10 mV, which were usually small when ICa was blocked, were potentiated if preceded by a voltage step to strongly positive potentials. This potentiation was inhibited by ryanodine, suggesting that Ca entry that occurs by Na-Ca exchange may be important for normal SR Ca loading.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Group-oriented fair exchange of signatures

2011 ◽  
Vol 181 (16) ◽  
pp. 3267-3283 ◽  
Author(s):  
Qiong Huang ◽  
Duncan S. Wong ◽  
Willy Susilo
Keyword(s):  
Fair Exchange
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