Tor is a popular anonymity-preserving network, consisting of routers run by volunteers all around the world. It protects Internet users’ privacy by relaying their network traffic through a series of routers, thus concealing the linkage between the sender and the recipient. Despite the advantage of Tor’s anonymizing capabilities, it also brings extra latency, which discourages more users from joining the network. One of the factors that causes the latency lies in Tor’s circuit scheduling algorithm, which allows busy circuits to crowd out bursty circuits. In this work, we propose and implement a more advanced scheduling algorithm which treats circuits differently, based on their recent activity. In this way, bursty circuits such as those used for web browsing can gain higher priority over busy ones such as used for bulk transfer; the performance for most activities over Tor is improved, while minimal overhead is incurred. Our algorithm has been incorporated into the latest build of Tor.

Tor is a popular anonymity-preserving network, consisting of routers run by volunteers all around the world. It protects Internet users’ privacy by relaying their network traffic through a series of routers, thus concealing the linkage between the sender and the recipient. Despite the advantage of Tor’s anonymizing capabilities, it also brings extra latency, which discourages more users from joining the network. One of the factors that causes the latency lies in Tor’s circuit scheduling algorithm, which allows busy circuits to crowd out bursty circuits. In this work, we propose and implement a more advanced scheduling algorithm which treats circuits differently, based on their recent activity. In this way, bursty circuits such as those used for web browsing can gain higher priority over busy ones such as used for bulk transfer; the performance for most activities over Tor is improved, while minimal overhead is incurred. Our algorithm has been incorporated into the latest build of Tor.

Anonymity on the internet is becoming a actuall issue nowadays. There are several tools, that can be used to monitor user's activity and it can lead to lose privacy of users. The aim of this master's thesis is to describe different ways of working anonymous systems, especially the method called Onion Routing. The introduction of this work is devoted to the description of this method together with asymmetric cryptosystem RSA. The second part belongs to basics of socket programming and to the implementation of anonymous system in programming language C++. The final part is focussed on analysis of system in terms of security and time complexity. The conditions of anonymity and decentralization are accomplished. There is no presence of central server in the system and the management is handled by signalling messages.

Cette thèse s'articule autour de deux parties, toutes deux liées à la protection de la vie privée dans les réseaux informatiques en général et sur l'Internet en particulier.<br /><br />Dans la première partie, nous proposons un système permettant d'établir des communications interactives non-observables, c'est-à-dire telles qu'un observateur ne puisse pas déterminer vers quelle(s) destination(s) sont établies ces communications, ni même, en fait, être certain qu'il y a bien de vraies communications!<br />Ce système innove par le niveau de protection qu'il vise, puisque même un observateur très puissant ne devrait pas être à même de la contourner.<br />Cette protection se base sur l'Onion-Routing et le complète avec des méthodes sophistiquées destinées à déjouer l'analyse de trafic.<br /><br />Dans la seconde partie, nous nous intéressons plus particulièrement au protocole DNS.<br />Bien qu'il soit possible de le protéger avec notre proposition de la partie précédente, cela dégrade ses performances (en termes de latence), ce qui à son tour a un impact sur celles des protocoles qui utilisent DNS.<br />Dans cette partie, nous proposons une solution spécifique à DNS, qui fournit à la fois un bon niveau de protection et de meilleures performances.<br /><br />Ces deux systèmes peuvent bien sûr se combiner, mais aussi être utilisés comme des briques séparées, avec d'autre mécanismes de protection de la vie privée.

V tejto práci sumarizujeme aktuálny výskum protokolov z rodiny Proof-of-Stake ako napr. Algorand, Tendermint a LaKSA. Analyzovali sme ich funkcionalitu a tiež ich problémy. V rámci výskumu sme implementovali a novy protokol z rodiny Dôkaz-Podielom, ktorý rieši nájdené problémy ako priepustnosť, škálovatelnosť a bezpečnosť.

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Master´s thesis focuses on certain possibilities of how user can anonymously commununicate through the Internet. There are described following anonymous programs: TOR, JAP, I2P and CyberGhost, which allow user to hide his own identity to other IP address. Subsequently, measurements from different technologies are made by anonymous program TOR for calculate transmission speed.

Freedom of speech and the right to privacy are maybe the most important elements of a modern society, yet the rights are often violated. This fact was the main reason for writing this thesis covering P2P network models, anonymity, censorship resistance and their use in real P2P networks and publishing systems. We discuss their effectiveness and suitability for specific purposes, but also the security considerations of their use. The second part of this thesis presents the LSPP publishing protocol, which is an library implementation of an anonymous censorship resistant P2P network. Finally, we analyze the proposed protocol and compare it with existing solutions.

Numerous mobile applications have the potential to collect and share userspecific information on top of the essential data handling. This is made possible through poor application design and its improper implementation. The lack of security and privacy in an application is of main concern since the spread of sensitive and personal information can cause both physical and emotional harm, if it is being shared with unauthorized people. This thesis investigates how to confidentially transfer user information in such a way that the user remains anonymous and untraceable in a mobile application. In order to achieve that, the user will first authenticate itself to a third party, which provides the user with certificates or random generated tokens. The user can then use this as its communication credentials towards the server, which will be made through the Tor network. Further, when the connection is established, the WiFi details are sent periodically to the server without the user initiating the action. The results show that it is possible to establish connection, both with random tokens and certificates. The random tokens took less time to generate compared to the certificate, however the certificate took less time to verify, which balances off the whole performance of the system. Moreover, the results show that the implementation of Tor is working since it is possible for the system to hide the real IP address, and provide a random IP address instead. However, the communication is slower when Tor is used which is the cost for achieving anonymity and improving the privacy of the user. Conclusively, this thesis proves that combining proper implementation and good application design improves the security in the application thereby protecting the users’  privacy. / Många mobilapplikationer har möjlighet att samla in och dela användarspecifik information, utöver den väsentliga datahanteringen. Det här problemet möjliggörs genom dålig applikationsdesign och felaktig implementering. Bristen på säkerhet och integritet i en applikation är därför kritisk, eftersom spridning av känslig och personlig information kan orsaka både fysisk och emotionell skada, om den delas med obehöriga personer. Denna avhandling undersöker hur man konfidentiellt kan överföra användarinformation på ett sätt som tillåter användaren av mobilapplikationen att förbli både anonym och icke spårbar. För att uppnå detta kommer användaren först att behöva autentisera sig till en tredje part, vilket förser användaren med slumpmässigt genererade tecken eller med ett certifikat. Användaren kan sedan använda dessa till att kommunicera med servern, vilket kommer att göras över ett Tor-nätverk. Slutligen när anslutningen upprättats, kommer WiFi-detaljerna att skickas över periodvis till servern, detta sker automatiskt utan att användaren initierar överföringen. Resultatet visar att det är möjligt att skapa en anslutning både med ett certifikat eller med slumpmässiga tecken. Att generera de slumpmässiga tecknen tog mindre tid jämfört med certifikaten, däremot tog certifikaten mindre tid att verifiera än tecknen. Detta resulterade i att de båda metoderna hade en jämn prestanda om man ser över hela systemet. Resultatet visar vidare att det implementeringen av Tor fungerar då det är möjligt för systemet att dölja den verkliga IPadressen och att istället tillhandahålla en slumpmässig IP-adress. Kommunikationen genom Tor gör dock systemet långsammare, vilket är kostnaden för att förbättra användarens integritet och uppnå anonymitet. Sammanfattningsvis visar denna avhandling att genom att kombinera korrekt implementering och bra applikationsdesign kan man förbättra säkerheten i applikationen och därmed skydda användarnas integritet.

Denna rapport beskriver arbetsgången för att utreda och ta fram ett lösningsförslag för hur en meddelandemotor skulle kunna implementeras i TeamTags delvis redan befintliga system. Små delar av implementeringen som infördes under projektet presenteras också. / This report describes the workflow to investigate and develop a solution proposal for how a messaging engine could be implemented in TeamTags partly already implemented system. Small parts of the implementation that was introduced during the project is also presented.