60 research outputs found

    An Empirical Study of the I2P Anonymity Network and its Censorship Resistance

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    Tor and I2P are well-known anonymity networks used by many individuals to protect their online privacy and anonymity. Tor's centralized directory services facilitate the understanding of the Tor network, as well as the measurement and visualization of its structure through the Tor Metrics project. In contrast, I2P does not rely on centralized directory servers, and thus obtaining a complete view of the network is challenging. In this work, we conduct an empirical study of the I2P network, in which we measure properties including population, churn rate, router type, and the geographic distribution of I2P peers. We find that there are currently around 32K active I2P peers in the network on a daily basis. Of these peers, 14K are located behind NAT or firewalls. Using the collected network data, we examine the blocking resistance of I2P against a censor that wants to prevent access to I2P using address-based blocking techniques. Despite the decentralized characteristics of I2P, we discover that a censor can block more than 95% of peer IP addresses known by a stable I2P client by operating only 10 routers in the network. This amounts to severe network impairment: a blocking rate of more than 70% is enough to cause significant latency in web browsing activities, while blocking more than 90% of peer IP addresses can make the network unusable. Finally, we discuss the security consequences of the network being blocked, and directions for potential approaches to make I2P more resistant to blocking.Comment: 14 pages, To appear in the 2018 Internet Measurement Conference (IMC'18

    Computer science and technology : historiography V (3)

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    I2P, X-Files season 10, video game writing credits..

    Measuring and Evading Turkmenistan's Internet Censorship: A Case Study in Large-Scale Measurements of a Low-Penetration Country

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    Since 2006, Turkmenistan has been listed as one of the few Internet enemies by Reporters without Borders due to its extensively censored Internet and strictly regulated information control policies. Existing reports of filtering in Turkmenistan rely on a small number of vantage points or test a small number of websites. Yet, the country's poor Internet adoption rates and small population can make more comprehensive measurement challenging. With a population of only six million people and an Internet penetration rate of only 38%, it is challenging to either recruit in-country volunteers or obtain vantage points to conduct remote network measurements at scale. We present the largest measurement study to date of Turkmenistan's Web censorship. To do so, we developed TMC, which tests the blocking status of millions of domains across the three foundational protocols of the Web (DNS, HTTP, and HTTPS). Importantly, TMC does not require access to vantage points in the country. We apply TMC to 15.5M domains, our results reveal that Turkmenistan censors more than 122K domains, using different blocklists for each protocol. We also reverse-engineer these censored domains, identifying 6K over-blocking rules causing incidental filtering of more than 5.4M domains. Finally, we use Geneva, an open-source censorship evasion tool, to discover five new censorship evasion strategies that can defeat Turkmenistan's censorship at both transport and application layers. We will publicly release both the data collected by TMC and the code for censorship evasion.Comment: To appear in Proceedings of The 2023 ACM Web Conference (WWW 2023

    Assessing the Privacy Benefits of Domain Name Encryption

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    As Internet users have become more savvy about the potential for their Internet communication to be observed, the use of network traffic encryption technologies (e.g., HTTPS/TLS) is on the rise. However, even when encryption is enabled, users leak information about the domains they visit via DNS queries and via the Server Name Indication (SNI) extension of TLS. Two recent proposals to ameliorate this issue are DNS over HTTPS/TLS (DoH/DoT) and Encrypted SNI (ESNI). In this paper we aim to assess the privacy benefits of these proposals by considering the relationship between hostnames and IP addresses, the latter of which are still exposed. We perform DNS queries from nine vantage points around the globe to characterize this relationship. We quantify the privacy gain offered by ESNI for different hosting and CDN providers using two different metrics, the k-anonymity degree due to co-hosting and the dynamics of IP address changes. We find that 20% of the domains studied will not gain any privacy benefit since they have a one-to-one mapping between their hostname and IP address. On the other hand, 30% will gain a significant privacy benefit with a k value greater than 100, since these domains are co-hosted with more than 100 other domains. Domains whose visitors' privacy will meaningfully improve are far less popular, while for popular domains the benefit is not significant. Analyzing the dynamics of IP addresses of long-lived domains, we find that only 7.7% of them change their hosting IP addresses on a daily basis. We conclude by discussing potential approaches for website owners and hosting/CDN providers for maximizing the privacy benefits of ESNI.Comment: In Proceedings of the 15th ACM Asia Conference on Computer and Communications Security (ASIA CCS '20), October 5-9, 2020, Taipei, Taiwa

    Datenschutzfördernde Techniken für private Dienste

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    Privacy on the Internet is becoming more and more important, as an increasing part of everyday life takes place over the Internet. Internet users lose the ability to control which information they give away about themselves or are even not aware that they do so. Privacy-enhancing technologies help control private information on the Internet, for example, by anonymizing Internet communication. Up to now, work on privacy-enhancing technologies has mainly focused on privacy of users requesting public services. This thesis introduces a new privacy risk that occurs when private persons run their own services. One example are instant messaging systems which allow users to exchange presence information and text messages in real time. These systems usually do not provide protection of presence information which is stored on central servers. As an alternative, decentralized instant messaging system designs mitigate this problem by having private persons provide instant messaging services to each other. However, providing a service as a private person causes new security problems as compared to providing a service as an organization or enterprise: First, the presence of such a service reveals information about the availability of the service provider. Second, the server location needs to be concealed in order to hide the whereabouts of a person. Third, the server needs to be specifically protected from unauthorized access attempts. This thesis proposes to use pseudonymous services as a building block for private services. Pseudonymous services conceal the location of a server that provides a specific service. The contribution made here is to analyze what parts of pseudonymous services, in particular Tor hidden services, are missing in order to apply them for private services. This analysis leads to three main problems for which solutions are proposed: First, known pseudonymous service designs do not scale to the expected number of private services which might be provided in the future. This thesis proposes a new approach to store hidden service descriptors in a distributed data structure rather than on central servers. A particular focus lies on the support of private entries which are required for private services. Second, pseudonymous services leak too much information about service identity during advertisement in the network and connection establishment by clients. The approach taken in this thesis is to reduce the information that a service publishes in the network to a minimum and prevent unauthorized clients from accessing a service already during connection establishment. These changes protect service activity and usage patterns from non-authorized entities. Third, pseudonymous services exhibit worse performance than direct service access. The contribution of this thesis is to measure performance, identify possible problems, and propose improvements.Privatsphäre im Internet wird immer wichtiger, da ein zunehmender Teil des alltäglichen Lebens über das Internet stattfindet. Internet-Benutzer verlieren die Fähigkeit zu steuern, welche Informationen sie über sich weitergeben oder wissen nicht einmal, dass sie dieses tun. Datenschutzfördernde Techniken helfen dabei, private Informationen im Internet zu kontrollieren, zum Beispiel durch die Anonymisierung von Internetkommunikation. Bis heute liegt der Fokus bei datenschutzfördernden Techniken hauptsächlich auf dem Schutz von Anfragen an öffentliche Dienste. Diese Arbeit wirft die Frage nach den Risiken beim Betrieb von Internetdiensten durch Privatpersonen auf. Ein Beispiel hierfür sind Instant-Messaging-Systeme, die es ermöglichen, Anwesenheitsinformationen und Textnachrichten in Echtzeit auszutauschen. Üblicherweise schützen diese Systeme die Anwesenheitsinformationen, die auf zentralen Servern gespeichert werden, nicht besonders. Als Alternative verringern dezentrale Instant-Messaging-Systeme dieses Problem, indem Privatpersonen sich gegenseitig Dienste anbieten. Allerdings bringt das Anbieten eines Dienstes als Privatperson im Vergleich zu Organisationen oder Unternehmen neue Sicherheitsprobleme mit sich: Erstens werden durch die Verfügbarkeit eines solchen Dienstes Informationen über die Präsenz des Dienstanbieters preisgegeben. Zweitens soll der Standort des Servers unerkannt bleiben, um nicht den Aufenthaltsort des Dienstanbieters zu offenbaren. Drittens muss der Server besonders vor unautorisierten Zugriffsversuchen geschützt werden. Diese Arbeit schlägt die Nutzung von pseudonymen Diensten als Baustein von privaten Diensten vor. Pseudonyme Dienste verbergen den Standort eines Servers, der einen bestimmten Dienst anbietet. Der hier geleistete Beitrag soll herausfinden, welche Teile von pseudonymen Diensten, besonders von Tor Hidden Services, fehlen, um sie für private Dienste einzusetzen. Dies führt zu drei Hauptproblemen, zu denen Lösungen vorgeschlagen werden: Erstens skalieren bisherige Ansätze für pseudonyme Dienste nicht für die in Zukunft zu erwartende Anzahl von privaten Diensten. Diese Arbeit schlägt einen neuen Ansatz vor, der Hidden-Service-Beschreibungen in einer verteilten Datenstruktur ablegt, anstatt sie auf zentralen Servern zu speichern. Ein besonderer Fokus liegt auf der Unterstützung von privaten Einträgen, die für private Dienste benötigt werden. Zweitens geben pseudonyme Dienste während des Anbietens im Netzwerk und der Verbindungsherstellung durch Clients zu viele Informationen über die Identität des Dienstes preis. Der in dieser Arbeit verfolgte Ansatz ist, die Informationen, die ein Dienst im Netzwerk bekanntgibt, auf ein Minimum zu reduzieren und nicht-autorisierte Clients am Zugriff auf den Dienst schon während der Verbindungsherstellung zu hindern. Diese Änderungen schützen die Aktivität und das Nutzungsmuster des Dienstes vor nicht-autorisierten Personen. Drittens weisen pseudonyme Dienste eine schlechtere Effizienz auf als Dienste, auf die direkt zugegriffen wird. Der Beitrag dieser Arbeit ist, die Effizienz zu messen, mögliche Probleme zu identifizieren und Verbesserungen vorzuschlagen
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