A Secure Peer-to-Peer Application Framework

The nature of the Internet has changed dramatically. From a modest research network, it has evolved into one of the most important fabrics of our modern society, affecting the lives of billions each day. We rely on it for everything from performing our daily chores to accessing rich media and keeping in touch with our friends. Despite this change, service provisioning has largely remained intact. Services are provided in a centralized manner, resulting in bottlenecks and vulnerable collections of, often unwittingly, submitted sensitive information. Peer-to-peer (P2P) technologies have the potential to provide a better alternative for future networking. P2P services distribute the load from a single node to a network of peers, relying on the resources of the end-users themselves. Not only does it remove the bottlenecks, it has the potential to provide a more personal and safe networking environment. In this dissertation, we inspect the feasibility and implications of a generic, cross-application, P2P framework. We present the design and implementation of a framework that uses existing infrastructure and advanced networking protocols to create a secure environment. Using this framework, applications are able to benefit from P2P networking without having to deploy new infrastructure or implement complex connection- and identity management. Users benefit from using a single, strong, cross-application identity management and having better control over their data. This improves the trust within the system and enables new ways of dealing with security threats. We demonstrate the feasibility of the framework by evaluating the performance and usability of the prototype implementation. This provides a model for future networking applications and insight into the security and usability issues these will face

A power market-based operation support model for sub-daily hydropower regulation practices

Highlights • Investigate the impact of instant energy demand on sub-daily river regime. • Introducing power market impact index. • Introducing system efficiency ratio index. • Provides an efficient tool for sustainable river management. • Assess the interaction of power market and regulation practices.With increasing power production from renewable energy sources, sub-daily variations in energy demand need to be balanced. Today, hydropower is commonly used as balancing power. In this study, we quantified the impact of capacity constraints, in terms of reservoir volume and hydropower capacity, on the potential to comply with instant energy demand. To evaluate the impact, we developed two new metrics, power market impact and system efficiency ratio, which are based on two threshold flow regimes derived from natural flow as lower threshold release and regulated flow (based on hourly energy prices) as upper threshold release. The operation support model comprises 96 different regulation scenarios based on varying combinations of hydropower and reservoir capacities. For each scenario, an hourly water balance was simulated, to obtain the highest complying with upper threshold release based on actual energy demand. We tested the framework on the Kemijoki river with defined thresholds based on the natural flow regime (tributary river Ounasjoki) and the hourly energy price in Finland in 2017, and estimated the impact of regulation on hourly flow regime at the Taivalkoski hydropower station. The annual flow regime impact in 2013, 2014 and 2015 was estimated to be 74%, 84% and 61%, respectively, while the monthly impact varied from 27% to 100%. Our framework for evaluating interactions between the power market and sub-daily regulation practices is a useful novel tool for sustainable river management and can be easily applied to different rivers and regions and evaluated for different timescales

Tiedonjakojärjestelmä langattomille laitteille

Nykyaikaiset älypuhelimet mahdollistavat käyttäjilleen monenlaisen tiedon välityksen. Tämänhetkisillä älypuhelinsovelluksilla, joita käytetään tiedon esittämiseen ja hallintaan, on vain rajatut toiminteet tiedon tuomiselle käyttäjälle. Tavallisesti tietoa haetaan vain käyttäjän aloitteesta ja tiedonsiirrossa käytetään mobiiliverkon operaattorin maksullisia palveluja. Tämä heikentää sovellusten käytettävyyttä ja haluttavuutta, mutta on kuitenkin kustannustehokasta, sillä älykkäitä, monikanavaisia tiedonsiirtoratkaisuja on hankala kehittää. Tämä diplomityö käsittelee konseptia yleisestä, laajennettavasta tiedonjakoalustasta langattomille laitteille. Alusta tarjoaa sovelluksille toimintoja kuten automaattiset päivitykset ja tiedon jakeluun vertaisverkkojen avulla. Alusta on suunniteltu käytettäväksi mahdollisimman pienillä muutoksilla olemassa oleviin sovelluksiin. Työssä esitellään myös Symbian-pohjainen prototyyppitoteutus alustalle. Konseptia tarkistellaan tutkimalla ratkaisuja samankaltaisiin ongelmiin perinteisissä tietoverkoissa ja analysoimalla näiden ratkaisujen soveltuvuutta mobiiliympäristöihin. Tämän tutkimuksen avulla luodaan vaatimukset mobiiliympäristössä toimivalle tiedonjakoalustalle. Tämän jälkeen esitellään alustan prototyyppitoteutus. Prototyypin avulla suoritettu lyhyt käyttäjätutkimus konseptin käytettävyydestä esitetään lopuksi. Tutkimuksen tulokset viittaavat siihen että oikein toteutettuna ja laajassa käytössä, tämänkaltainen alusta voisi parantaa älypuhelimien käytettävyyttä tietyissä yhteyksissä

Cyclic ranking in single-resource peer-to-peer exchange

Peer-to-peer (P2P) sharing systems use incentives for resource exchange to encourage cooperation and ensure fairness. In bilateral strategies, such as BitTorrent Tit-for-Tat or deficit-based FairTorrent, individual decisions of peers utilize direct observations. It may result in low performance and unfair treatment. In this paper, we study a novel exchange strategy that applies Cyclic Ranking (CR). In addition to direct observations, a peer utilizes provision cycles---a shared history of effective exchanges. The PageRank algorithm runs for the locally collected cycles and computes the numerical ranks to estimate the reputation. The CR strategy incrementally augments known incentive-aware strategies. For evaluation we implement CR-BitTorrent and CR-FairTorrent variants. Our simulation model captures the dependence on network bandwidth and the number of seeders as well as selfishness and stability of the participants. The initial experiments show improved fairness and download times, compared to the original BitTorrent and FairTorrent. The performance of selfish and unstable peers decreases by as much as 50%. The CR strategy suits well in environments where direct reciprocity has shown little effect. Contrasted to existing solutions, the CR strategy rewards longevity and stability of peers.Peer reviewe

Seroepidemiology of the human polyomaviruses.

To assess the stability of polyomavirus antibodies in serial samples over time and the incidence and age-specific prevalence of polyomavirus infections, we established enzyme immunoassays (EIAs) using purified yeast-expressed virus-like particles (VLPs) containing the VP1 major capsid proteins of JC virus (JCV) and the AS and SB strains of BK virus (BKV). A random subsample of 150 Finnish women who had serum samples taken during the first trimester of pregnancy and had a second pregnancy during a 5 year follow-up period was selected, grouped by age of first pregnancy. The polyomavirus antibody levels were similar in samples taken during the first and second pregnancies (correlation coefficient 0·93 for BKV SB and 0·94 for JCV). Analysis of serum samples from 290 Swedish children aged 1–13 years, grouped by age in 2 year intervals, demonstrated that BKV seropositivity increased rapidly with increasing age of the children, reaching 98 % seroprevalence at 7–9 years of age, followed by a minor decrease. JCV seroprevalence increased only slowly with increasing age and reaching 72 % positivity among mothers >25 years of age. The age-specific seroprevalence of the human polyomaviruses measured using this VLP-based EIA was similar to previous serosurveys by other methods. The stability of the antibodies over time indicates that polyomavirus seropositivity is a valid marker of cumulative virus exposure, and polyoma VLP-based EIAs may therefore be useful for epidemiological studies of these viruses